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When to Use guardrail spacer？

16 Jun.,2025

Guard rail support, attachment, and positioning spacer block

USB2 - Guard rail support, attachment, and positioning spacer block - Google Patents

Guard rail support, attachment, and positioning spacer block Download PDF

Info

Publication number: USB2
Authority: US; United States
Prior art keywords: spacer block; block; spacer; face; tab
Prior art date: -11-15
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.): Expired - Lifetime

Application number

US10/001,903

Other versions

USA1 (en

Inventor

David T. King

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

K E S S Inc

Original Assignee

K E S S Inc

Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)

-11-15

Filing date

-11-15

Publication date

-07-06

-11-15 Application filed by K E S S Inc filed Critical K E S S Inc

-11-15 Priority to US10/001,903 priority Critical patent/USB2/en

-02-20 Priority to US10/079,280 priority patent/USB2/en

-06-03 Assigned to TRINITY INDUSTRIES, INC. reassignment TRINITY INDUSTRIES, INC. LICENSE (SEE DOCUMENT FOR DETAILS). Assignors: KING, DAVID T.

-07-18 Publication of USA1 publication Critical patent/USA1/en

-02-03 Assigned to K.E.S.S. INC. reassignment K.E.S.S. INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KING, DAVID T.

-03-10 Priority to US10/385,006 priority patent/USA1/en

-07-06 Application granted granted Critical

-07-06 Priority to US10/885,398 priority patent/USA1/en

-07-06 Publication of USB2 publication Critical patent/USB2/en

-11-15 Anticipated expiration legal-status Critical

Status Expired - Lifetime legal-status Critical Current

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Classifications

- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
- E01F15/00—Safety arrangements for slowing, redirecting or stopping errant vehicles, e.g. guard posts or bollards; Arrangements for reducing damage to roadside structures due to vehicular impact
- E01F15/02—Continuous barriers extending along roads or between traffic lanes
- E01F15/04—Continuous barriers extending along roads or between traffic lanes essentially made of longitudinal beams or rigid strips supported above ground at spaced points
- E01F15/—Metal rails
- E01F15/—Spacers between rails and posts, e.g. energy-absorbing means

Definitions

This device relates to spacer blocks for attachment of guard rails to support posts.
Guard rails are typically installed along highways as a roadway safety barrier system.
the guard rails are usually formed as strips of material, typically extruded metal about 12 feet long and weighting about 90 pounds.
a preferred embodiment comprises an elongated strip of metal, usually composed of galvanized steel, (typically about 12 gauge), aluminum, steel, fiber glass, or even synthetic materials.
At least one configuration of a guard rail used includes a corrugation forming an undulating cross section in order to absorb energy upon receiving an impact from an out of control vehicle to prevent or at least control the direction of the vehicle prior to its leaving the roadway.
these beams are about 9 inches wide, have two crowns and are shaped substantially like the letter “W”.
An alternate corrugated guard rail is known in the industry as a thrie beam which has three crowns and is about a third wider than the conventional two crown guard rail.
a plurality of guard rails will be linked together horizontally at their distal ends, either end to end, or overlapping, and be supported by a plurality of vertically oriented posts which are typically “I-beamed” shaped, round, or square posts which are driven into the ground spaced apart a selected distance from the edge of the road.
posts are also fabricated from aluminum, wood, or other metals and could be formed from polymers or fiberglass materials.
the posts are usually driven into the ground and typically will yield under a desired amount of pressure and move within the ground or bend in accordance with the deformation of the guard rail rather than break off at ground level, in order to assist the rail in dissipating force upon receiving a blow from a vehicle.
a spacer block is disposed between the guard rail and the post to support the guard rail at a selected distance from the post to prevent an uncontrolled vehicle from hitting and entangling the posts.
the spacer block keeps the automobile wheels from impacting the posts and initiating a roll of the vehicle.
the guard rail provides a continuous rail or track for guiding the vehicle providing at least some response time for the driver to regain control of the vehicle before leaving the roadway.
wood The most popular material spacer blocks are made out of is wood. Some of the problem with wood is it deteriorates over time, it is heavy, it can give installers splinters, it contracts and expands with season changes. Also, wood tends to leach out chemicals typically used for pressure treating which may be toxic to the environment. Conventional plastic blocks on the market today are typically wood block designs made out of plastic.
the instant invention provides a spacer block having improved strength, reduced weight, and competitive cost. Furthermore, the spacer block of the present invention was designed with the assembly process in mind in order to enable a single individual to erect a guard rail safety barrier system on spacer blocks supported by posts.
the guard rail support attachment and positioning block or spacer block is used to space guard railing away from posts such as “I” beams which are driven into the ground.
the spacer block of the instant invention provides a design that is strong yet light, which makes it installation friendly, reduces the cost of manufacture, and permits one person to install a section of guardrail. In the past it might require two or three people to hold the rail and mount it to the spacer block and support post.
Plastic properties are different from wood and requires a design that takes advantage of the different properties.
the present design is specific for plastic, (polyethylene, PVC, polypropylene polyethylene terphthalate, nylon), or plastic/rubber and will out perform the wood design in all performance specifications.
the resiliency, elasticity, flexibility, and ability to be impervious to weathering elements, extend longtivity, and require little or no maintenance are important features of the present invention.
a preferred embodiment to the spacer block of the instant invention is a generally rectangular block or cube including corded-out cavities to reduce weight and one or more tabs on the top and/or sides projecting outwardly for cooperatively engaging the sides and top edge of the post.
a preferred embodiment is approximately 4 inches in width which is the same as conventional I-beam posts providing a lightweight, compact, high strength spacer block as compared to conventional spacer blocks made from wood or plastic typically having a width of 6 inches or more.
a tab projecting outward from the face of the spacer block provides a support member to hold, steady, and even align the guard rail which rests thereon providing a means for one individual to mount the guard rail on spacer blocks, whereas conventional spacer blocks do not support the guard rail prior to attachment thereto and require at least two individuals if not three to attach the guard rail to the spacer block and post.
the preferred embodiment of the spacer block of the present invention comprises one or more polymers, such as (polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, and mixtures thereof), and preferably a polymer/rubber blend.
polymers such as (polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, and mixtures thereof), and preferably a polymer/rubber blend.
Other plastic materials which may be used may be selected from ABS, Acetyl, polypropylene oxide, nylon PBT, polycarbonate, polystyrene, modified polyphenylene oxide, polyester, fiberglass filled nylon, fiberglass filled styrene, fiberglass filled SAN, acrylic, ethylene copolymers, ionomers, and polysulfone.
the spacer block of the present invention may be formed of a single type of polymer or mixtures of various polymers.
the polymers may be virgin material or the spacer block may be composed of at least some if not all of regrind materials, such as reground polyethylene, ethylene.
the rubber and/or elastomeric compound which can be incorporated in the formulation may be comprised of a natural rubber or synthetic rubber, either virgin, regrind material or combinations thereof. It is contemplated that fiberglass may also be used as an additive or substitute raw material for all or at least a portion of the plastic material. Fillers such as wood chips. sawdust, calcium carbonate may also be used.
the rubber from used tires have been a huge problem for the environment and could be utilized as the source of rubber for the instant invention.
the spacer blocks may themselves be recyclable.
One preferred embodiment of the present invention is a spacer block utilizing a blend of at least one polymer including one or more of the plastic materials set forth heretofore, together with at least one rubber or elastomeric materials mixed and molded together with the polymer(s).
the ability to mold large blocks of plastic containing virgin, and/or regrind thermoplastics which can be obtained from reusable containers, alone or together with virgin or grind rubber from used tires or other sources providing a useful means of disposal and recycling of waste products.
One preferred embodiment of the invention utilizes grind rubber in combination with a one or more thermoplastics extruded or molded by low pressure injection molding or vacuum forming.
the molding process is believed to encapsulate the rubber particles with the thermoplastic melt thereby providing a stronger blended product with enhanced performance capabilities as compared to a simple mixture of thermoplastic and rubber particles compressed together under high pressure.
One source of the grind rubber is reground vehicle tires, representing a new method of disposal of used tires.
Another important aspect of the present invention is the molding of the spacer blocks using a structural foam process to further increase strength, reduce costs, and reduce the weight of the spacer blocks.
the structural foam techniques utilizes a gas and/or chemical foaming agent injection process in the molding operation to form a foam core creating structural support webbing between solid plastic skins to increase structural strength and reduce weight and cost.
the design of the block to include structural external webbing between void spaces in the spacer blocks of the instant invention further provides strength and weight advantages to the space block.
the use of the blend of plastics and rubber and/or the webbing within the block cavity are unique features; however, in addition the utilization of structural foam forming the skin provides another novel feature not utilized in spacer blocks taught in the prior art.
all or at least a portion of the spacer block 10 could be filled with foam, gel, finely ground solid material, or even a liquid such as water and/or alcohol and water such as a glycol to inhibit freezing, or that the cavity could contain a bag containing same to cushion and absorb impact thereto.
the material could be contained within the spacer block body or insertion of a container into the webbing or cavity formed within the spacer block could even be removable, such as a water bag or a deformable plastic container such as a jug.
a cellular core could be utilized for impact absorption within the cavities, or an impact absorbing block filled with cellular material, a gel, or a liquid could be disposed within the cavities formed in the present spacer blocks.
the instant invention includes a hanger enabling the spacer block to hang on the I beam by itself.
a guard rail resting tab On the bottom of the spacer block is a guard rail resting tab so that the guard rail can be lifted and placed on the resting tab for mounting to the spacer block and post.
One person can install a section by placing the bolt with in hands reach, it is possible for one person to lift a section of guardrail and rest it on the rail tab and install the bolt.
a section of guardrail can be installed by a single person at a much faster pace than the designs of today. Therefor, it is an objective of the present invention to provide a spacer block which enables one person to mount a guard rail to a spacer block and post.
Another important optional feature is the utilization of a plastic/rubber copolymer material to enhance the performance of the spacer block.
Yet another object of the present invention is to provide an embodiment which may be formed from structural foam in order to optimize the weight to strength of the spacer block.
FIG. 1 is a perspective view showing the spacer block of the present invention mounted to a post and cooperatively engaging a guard rail;
FIG. 2 is a rear perspective view showing the spacer block of FIG. 1 and the post;
FIG. 3 is a rear perspective view showing the spacer block of FIG. 1 having a cavity formed between the top, side, and medial wall, and a cavity formed between the medial side, and bottom wall;
FIG. 4 is a front perspective view of FIG. 1 showing the flat face of the spacer block and guard rail support and positioning tab;
FIG. 5 is perspective rear view showing an alternate embodiment of the spacer block utilizing a plurality of tabs removably and slidably positional within grooves formed in the top surface of the spacer block;
FIG. 6 is front view of an alternate embodiment of the spacer block showing webbing within the cavities
FIG. 7 is front view of an elongated embodiment of the spacer block utilizing the webbing arrangement of FIG. 6 for use with a thrie beam spacer block;
FIG. 8 is front view of an alternate embodiment of the spacer block showing a different webbing arrangement within the cavities
FIG. 9 is a side view of the spacer block of FIG. 8 formed of structural foam
FIG. 10 is front view of an elongated embodiment of a spacer block utilizing the webbing arrangement of FIG. 8 for use with a thrie beam spacer block;
FIG. 11 is a sectional view of a portion of a block showing a cellular core and an integral solid skin on each side thereof;
FIG. 12 is a sectional view along Section 9 — 9 of FIG. 9 showing a structural foam segment showing a cellular core and an integral solid skin, wherein the transition from skin to core is gradual;
FIG. 13 is a perspective view showing the spacer block of FIG. 12 mounted to a post and cooperatively engaging a guard rail;
FIG. 14 is a rear perspective view showing the spacer block of FIG. 12 and the post.
the structural integrity of the various embodiments of the spacer blocks 10 of the present invention is attributed to the lightweight composite materials and the reinforcing webbing which provides the rigidity and controlled compression of the spacer blocks 10 under load.
the spacer block 11 is mounted to a post 30 , shown as an I-beam, and cooperatively engages and supports a guard rail 14 having an “M” shaped corrugated cross section.
the spacer block 11 is shown with the removable slidable top tab 40 engaging the top edge of the I beam and the optional side tabs 42 preventing lateral movement thereof.
the guard rail 14 is shown resting, positioned on the bottom tab 64 extending from the spacer block 11 supporting and aligning the guard rail 14 for attachment to the post 30 with one or more bolts extending through the through holes or bores 28 of the spacer block 11 .
Conventional I-beam posts 30 have a single hole punched into the flange 54 on one side of the post 30 only.
the spacer block 10 used for conventional two crown guard rails or other conventional longitudinal rail members is typically about four (4) inches wide, about seven and one-half (71 ⁇ 2) inches deep, and about 14 inches long.
the spacer blocks 10 of the present invention include a front face 12 constituting the surface for attachment of the guard rail 14 .
the front face 12 is a generally flat solid surface. Of course it is anticipated that the face 12 could be webbed, curved, or even corrugated to correspond to the shape of the guard rail 14 .
the front face 12 can be formed to be concave and include a longitudinal depression to fit around posts as well.
the front face 12 is connected to a rear face 16 by a pair of spaced apart opposing side walls 18 to a top panel 20 and a bottom panel 22 .
the interconnecting side walls 18 , top panel 20 , and bottom panel 22 may have rounded shoulders 24 as shown in FIGS. 1-4 or squared shoulders 26 as shown in FIG. 5 .
the spacer block 11 can include a top cavity 34 and a bottom cavity 36 separated by a horizontally disposed medial wall 38 joining the front face 12 and rear face 16 , defining a pair of sleeves having bores 18 therethrough.
the corded-out cavities of the spacer block can be reinforced with webbing, solid block materials, gel material, foam, or liquids such as water, glycol, and mixtures thereof to aid in the dissipation of any stress.
An important feature of a preferred embodiment of the spacer block 11 of the present invention is a pair of mounting bores 28 formed in the spacer block 11 oriented along the horizontal axis, side by side, to facilitate aligning a bore 28 of the spacer block 11 with the offset hole 55 preformed in the typical metal I-beam 30 .
the bore 28 can be positioned for quick alignment and attachment of the spacer block 11 and guard rail 16 to the post 30 .
the spacer blocks 11 can include at least one and preferably a plurality of mounting bores 28 extending through the front face 12 for cooperative engagement of a corresponding bolt extending through the guard rail 14 and spacer block 11 for attachment to a post 30 .
the bore 28 extends through both the front face 12 and the rear face 16 .
the bore 18 can extend through the medial wall 38 interconnecting the front face 12 and the rear face 16 .
a sleeve 32 formed from a cylinder having a bore therethrough could be utilized as a removable spacer means for insertion between the hole formed in the front face 12 and rear face 16 abutting an interior surface of the front face 12 , extending through the cavity formed in the interior of the block 11 to interconnect with the interior surface of the rear face 16 to provide additional structural support.
a feature which is very useful and adaptable to the various spacer block 11 embodiments are locating and holding means for cooperatively engaging the post 30 and/or guard rail 14 .
the preferred embodiments of the spacer blocks 11 can include a top tab 40 fixedly attached to the top surface of the top panel 20 .
the tab 40 may also be provided as a removable or slidable tab having projections cooperatively engaging grooves formed in the channel 43 in a tongue and groove arrangement.
the tabs 43 extend from past the rear face 22 of the spacer block for holding the spacer block 11 onto the top of a post 30 . It is contemplated the tab 40 could comprise a flat plate or even a ring to engage a cylindrical post; however, the embodiment shown in FIGS.
1-5 includes projecting members or fingers 50 extending downward from the tab 40 mounted on the top of the block 11 extending past the rear face 22 enabling the tab 40 to set on top of an I-beam shaped post 30 with the fingers 50 extending behind the flanges 54 of the post 30 thereby holding the spacer block 11 securely to the post 30 for mounting.
a groove or channel 43 can be formed or cut into the surface of the spacer block 11 top panel 20 to facilitate molding or handling of the blocks.
a leg 48 can extend from the bottom surface of the tab 40 to be supported by and preferably to connect with the top of the channel 43 in order to provide additional structural support for the tab 40 .
a first and second channel, 56 and 58 respectively, are formed in the top panel 20 of the spacer block 13 .
a pair of tabs 41 and 46 fixedly attached to the top surface of the top panel 20 extend past the rear face 22 of the spacer block for holding the spacer block 13 onto the top of a post 30 .
the tabs 41 and 46 may also be provided as a removable or slidable tab having projections cooperatively engaging grooves formed in the channels 56 and 58 in a tongue and groove arrangement.
the tabs 41 and 46 extend from past the rear face 22 of the spacer block 13 for holding the spacer block 13 onto the top of a post 30 .
the top tab 42 allows the spacer blocks 13 to hang on the post 30 during mounting of the guard rail, post, and spacer block assembly.
a stop means may be incorporated within the channel or attached to the ends thereof to limit movement of a movable top tab 40 , 41 , and 46 .
FIGS. 6-14 show the use of side flanges 45 .
the side tabs 44 or side flanges 45 are spaced apart generally opposing one another and preferably in alignment with one another; however, it is not necessary that the side tabs 44 align with one another or that there be a corresponding number of side tabs on each side. Even one side tab 44 or side flange 45 aids in positioning the spacer blocks 10 with respect to the post 30 .
the side tabs 44 or side flanges 45 can be integrally formed within the spacer block 10 or attached by holding means such as a screw or projection engaging a hole formed in the spacer block 10 .
the spacer block 10 can be aligned in proper orientation by utilizing the side tabs 42 extending from the sides of the block 10 .
a support tab 64 can be provided extending from the bottom panel 22 of the front face 12 for supporting a guard rail 14 resting thereon and aiding in the alignment of the bores 28 with holes in the guard rail 14 and post 30 .
a recess or notch 60 can be formed or cut into the bottom edge panel 22 and rear face 16 of the spacer block 10 disposed therein for cooperatively engaging the support tab 64 permitting stacking and nesting of the spacer blocks 10 one upon the other for storage or transport.
FIGS. 6 and 8 show alternate embodiments of the spacer block of the present invention which utilize webbing within the top cavity 34 and bottom cavity 36 separated by a horizontally disposed medial wall 38 joining the front face 12 and rear face 16 , defining a pair of sleeves formed as cylinders having bores 18 therethrough.
FIGS. 6 and 8 A preferred configuration of webbing design is shown in FIGS. 6 and 8, wherein the rear end of the spacer block shows webbing formed by various lengths of lateral, longitudinal, and transverse members having cavities thereinbetween are formed to increase the structural strength while controlling compression and flexing forces and minimizing the weight of the spacer block.
a spacer block 70 includes webbing which extends from the interior surface of the front face 12 through the cavity 34 or 36 having a distal end equal distance with the side walls 18 forming the rear face 16 .
Extending from the center of the interior surface of the front face 12 and through the first cavity 34 is a first cylindrical reinforcement member 72 .
a corresponding second cylindrical reinforcement member 74 extends from the interior surface of the front face 12 through the second cavity 36 .
the webbing comprises runners extending radially from a cylindrical reinforcing members 72 , 74 to intersect with the interior surface of either the side wall 18 , top panel 20 , bottom panel 22 , or medial wall 38 .
a first runner 76 extends vertically from the top panel 20 to intersect with the cylindrical reinforcing member 72 .
a pair of second runners 78 extend radially from the cylindrical reinforcing member 72 toward the corners connecting the top panel 20 with the side wall 18 .
a pair of third runners 80 radiate horizontally from the cylindrical reinforcing member 72 toward the side walls 18 .
a fourth pair of runners 82 radiate downwardly from the cylindrical reinforcing member 72 toward the bores 28 in the medial wall 38 forming a tear drop shaped cavity thereinbetween.
a first runner 176 extends vertically from the bottom panel 22 to intersect with the cylindrical reinforcing member 74 .
a pair of second runners 178 extend radially from the cylindrica reinforcing member 74 toward the corners connecting the top panel 20 with the side wall 18 .
a pair of third runners 180 radiate horizontally from the cylindrical reinforcing member 74 toward the side walls 18 .
a fourth pair of runners 182 radiate downwardly from the cylindrical reinforcing member 172 toward the bores 28 in the medial wall 38 forming a tear drop shaped cavity thereinbetween.
spacer block 70 can be formed or molded having a front face 12 which is slightly shorter than the rear face 16 so that the top panel 12 or bottom panel 22 incline toward one another slightly at the front face 12 to facilitate removing the spacer block from the mold.
the notch (not shown) of the spacer block 70 is formed on the bottom of the bottom panel as a declining channel extending from the rear face 16 toward the front face 12 which does not extend through the interior surface of the bottom panel 22 .
FIG. 7 shows an alternate elongated embodiment of a spacer block 84 for use with thrie beam guard rails.
the elongated spacer block 84 includes an additional third center cavity 35 , medial wall 138 and bores 128 , disposed between the first top cavity 34 and the second bottom cavity 36 .
the spacer block 84 utilizes substantially the same webbing configuration of the spacer block 70 of FIG. 6 .
the spacer block 84 is approximately 4 inches wide, about 21 inches long, and about 71 ⁇ 2 to 8 inches thick.
the depth and length dimension could vary on any of the spacer blocks 10 depending upon the dimensions of the selected guard rail; however, the four inch wide dimension, although not critical is preferably maintained at about 4 inches or equivalent to the thickness of the mounting post excluding the side rails 45 or side tabs 42 .
a pair of runners 278 radiating upwardly from the cylindrical reinforcing member 172 toward the bores 28 in the medial wall 38 forming a tear drop shaped cavity thereinbetween.
a pair of runners 280 radiate horizontally from the cylindrical reinforcing member 274 toward the side walls 18 .
a pair of runners 282 radiate downwardly from the cylindrical reinforcing member 274 toward the bores 128 in the medial wall 138 forming a tear drop shaped cavity thereinbetween.
the spacer block embodiment 86 has similar dimensions, features, and webbing to that of the spacer block 84 . As best illustrated in FIGS. 8 and 9, it differs from spacer block 84 in that spacer block 86 does not utilize runner 76 extending vertically from the top panel 20 to intersect with the cylindrical reinforcing member 74 or the vertical runner 176 extending vertically from the bottom panel 22 to intersect with the cylindrical reinforcing member 74 . Moreover, the notch 260 is formed or cut into the bottom edge panel 22 and rear face 16 of the spacer block 10 forming a pocket, and does not cut through the bottom panel 22 exterior surface.
FIG. 10 shows an alternate elongated embodiment of the spacer block 86 for use with thrie beam guard rails.
the elongated spacer block 88 includes an additional third center cavity 35 , medial wall 138 and bores 128 , disposed between the first top cavity 34 and the second bottom cavity 36 .
the spacer block 88 utilizes substantially the same webbing configuration of the spacer block 86 of FIG. 8 .
the spacer block 88 is approximately 4 inches wide, about 21 inches long, and about 71 ⁇ 2 to 8 inches thick.
the depth and length dimension could vary on any of the spacer blocks 10 depending upon the dimensions of the selected guard rail; however, the four inch wide dimension, although not critical is preferably maintained at about 4 inches or equivalent to the thickness of the mounting post excluding the side rails 45 or side tabs 42 .
the structural foam spacer blocks of the present invention are molded and have a cellular core and an integral solid skin, wherein the transition from skin to core is gradual as shown in FIG. 11 .
the solid skin gives the molded part its form and toughness, while the cellular core contributes to the high strength to weight characteristics.
the skin of the structural foam spacer blocks can be up to 1 ⁇ 2 inch thick, more preferably up to 1 ⁇ 4 inch thick and most preferably up to 1 ⁇ 8 inch thick.
Thermoset materials such as polyurethane is produced by polyaddition of reactive components such as polyol and isocyanate. The exotherm generated by the reaction vaporizes a blowing agent that causes the mixture to expand.
Thermoplastic materials typically require the addition of physical or chemical blowing agents to product a foam and do not undergo chemical change. Some blowing agents decompsoe when heated to process temperature to evolve a gas such as carbon dioxide. Often sodium bicarbonate or ammonium carbonate is used for cellular or sponge rubber, halocarbons and methylene chloride is used in urethane, pentane in expanded polystyrene, and in some cases hydrazine for foamed plastics.
Spacer blocks utilizing plastic and/or rubber components formed with solid walls usually does not exceed 4 mm (0.16 inches).
the wall thickness of the spacer block composed of plastic and/or rubber components is usually not less than about 4 mm in order to gain the full advantage of the foam webbing structure between the two layers of skin.
thick wall thicknesses may be obtained using structural foam.
structural foam spacer blocks have few if any sink marks due to the residual gas pressure in the cells, which allows the material to expand internally while the part cools, thus holding the skin firmly against the mold walls. Because of their cellular structure the spacer blocks formed of structural foam are virtually stress-free, resulting in bowing and warpage being greatly reduced.
the properties of the structural form spacer block depends on the base polymer, overall part density, density distribution, skin thickness, cell shape and size. All of these parameters are affected by the processing method, process variables, wall thickness, and mold design.
Density of the structural foam varies across the cross section and is lowest in the core. As the distance from the center of the foamed block increases, the cells get smaller until they disappear completely in the outer skin.
the objective is to produce a part with high skin density and very low core density without the presence of voids.
the range of the density varies in the present invention from about 30 percent in the center to 100 percent at the outer skin.
the overall part density, density distribution, skin thickness, cell shape and size depend upon the mold cycle which may vary between 1 ⁇ 2 to 10 minutes.
a preferred embodiment of the spacer block of the instant invention is processed using a low pressure injection molding machine using thermoplastics and/or rubber.
a screw is used to plasticate a mixture of polymer and chemical blowing agent of up to 1% and preferably up to 1 ⁇ 2 percent wherein the screw barrels has zones at different temperatures arranged so that the blowing agent in only near the nozzle.
a foamable mixture is produced and pumped under pressure to an accumulator an stored in a molten state at a pressure higher than the foaming pressure. Upon opening a valve in the nozzle, a portion of the foamable mixture is discharged from the accumulator into the mold.
the mold cavity is filled by the gases generated by the decomposition of the chemical blowing agent forcing the material into the shape of the mold.
the structural foam blocks 10 of the present invention can be made utilizing of a rubber compound in combination with a plastic.
the plastic tends to encapsulate the rubber particles and act as a binder.
the rubber produces enough gas during processing under the heat and pressure of the low pressure injection molding process that the structural foam product can be made without the addition of any type of chemical blowing agent.
the spacer block of the present invention may be formed by injection molding, and preferably low pressure injection molding such as is used for structural foam products.
the spacer block can be comprised of a virgin or regrind plastic or combinations thereof without any rubber.
the plastic may be selected from the following polymers: polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, ABS, Acetyl, polypropylene oxide, nylon, PBT, polycarbonate, polystyrene, modified polyphenylene oxide, polyester, fiberglass filled nylon, fiberglass filled styrene, fiberglass filled SAN, acrylic, ethylene copolymers, ionomers, and polysulfone.
the spacer block of the present invention may be formed of a single type of polymer or mixtures of various polymers.
a chemical blowing agent in an amount of less than 5 percent, and more preferably in an amount of less than 1 percent and most preferably in amount of less than 1 ⁇ 2 percent can be used with the 100% polymer composition spacer blocks 10 .
a rubber and/or elastomeric compound can be incorporated in the formulation as a substitution for up to at 70 percent, and more preferably at less than 50% and most preferably from about 40 to 50 percent depending upon the strength to weight ratio desired and the structural properties required for a particular application or size of guard rail.
Regrind rubber is typically less expensive than plastic materials therefor, as much as 40 to 50 percent rubber may be used in spacer blocks for normal impact applications or posts spaced closed together, whereas a composition with less than 45 percent rubber may be desired for applications requiring the posts to be spread further apart from one another.
the type of rubber is also an important consideration in that the rubber may be comprised of a natural rubber or synthetic rubber, either virgin, regrind material or combinations thereof.
Additives such as fillers and fiberglass may further reduce the cost of manufacture and provide the requisite strength. Moreover, because of the gases produced from injection molding the rubber particles, the use of a chemical blowing agent is an option and is not required when processing the plastic and rubber mixed compositions.
a particular preferred embodiment comprises polyethylene together with grind rubber ranging in an amount of up to 45 percent. Yet another more preferred embodiment utilizes from about 30 to 45 percent regrind rubber and utilizes ethylene as the binding polymer.
PPT-SYS powdered processing aid from Polymer Process Technologies, Inc. in Akron, Ohio referred to by the trademark PPT-SYS, (PPT-SYS(R) for rubber applications and PPT-SYS(P) for plastic applications), having a specific gravity of about 1.01, pH of about 7, melting point range of over 600° F. which is a highly effective alloying agent for compatibilizing and alloying cured rubber, virgin or regrind, with plastic powder to form compounds having little or no change in physical properties.
another preferred embodiment may contain a nontoxic blend of naturally occurring materials, (plant polymers, gums, and anionic salts), marketed by Polymer process Technologies, Inc, under the trademark of PPT-RNU that when added to post consumer plastics of all kinds, will repair heat history plastics to near virgin polymer condition. in addition to or instead of the PPT-SYS (R)/(P).
the material has a pH of about 6.8, a specific gravity of about 1.05, a melt point flow of over 650° F. and used in amounts of up to 10% by weight and more preferably from about 3 to about 6% by weight.
Another preferred embodiment utilizes both the PPT-RNU and PPT-SYS additives with rubber and a polymer such as polyethylene to enhance the compatibility and performance of regrind rubber from tires being compounded with virgin or recycled polymers such as polyethylene in conventional compounding equipment at processing temperatures of from about 360° to 410° F. which is typical for extrusion and compounding operations.
a polymer such as polyethylene

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Engineering & Computer Science (AREA)
Architecture (AREA)
Civil Engineering (AREA)
Structural Engineering (AREA)
Refuge Islands, Traffic Blockers, Or Guard Fence (AREA)
Injection Moulding Of Plastics Or The Like (AREA)
Structure Of Exchanges (AREA)
Road Signs Or Road Markings (AREA)
Spinning Or Twisting Of Yarns (AREA)

Abstract

The guard rail support attachment and positioning block or spacer block is used to space guard railing away from posts such as “I” beams which are driven into the ground. The spacer block keeps automobile wheels from impacting the I beams and initiating a roll of the vehicle. The spacer block is a generally rectangular block or cube including corded-out cavities to reduce weight and tabs or projections which cooperatively engage the side of the post and the edge of the guard rail to position and hold same in position for attachment with holding members such as bolts. Webbing can be used to provide structural support within the cavity. The spacer block may be formed by low pressure injection molding to form a structural foam spacer block to optimize the strength to weight characteristics of the spacer block. The spacer block may be formed of a virgin and/or recycled plastic material and/or include virgin or recycled rubber material such as from obtained from the regrind of used tires and/or another elastomeric material from other sources.

Description

This application claims priority from U.S. provisional application Serial No. 60/249,037 filed on Nov. 15, . BACKGROUND OF THE INVENTION 1. Technical Field This device relates to spacer blocks for attachment of guard rails to support posts. 2. Description of the Prior Art Guard rails are typically installed along highways as a roadway safety barrier system. The guard rails are usually formed as strips of material, typically extruded metal about 12 feet long and weighting about 90 pounds. A preferred embodiment comprises an elongated strip of metal, usually composed of galvanized steel, (typically about 12 gauge), aluminum, steel, fiber glass, or even synthetic materials. At least one configuration of a guard rail used includes a corrugation forming an undulating cross section in order to absorb energy upon receiving an impact from an out of control vehicle to prevent or at least control the direction of the vehicle prior to its leaving the roadway. Typically these beams are about 9 inches wide, have two crowns and are shaped substantially like the letter “W”. An alternate corrugated guard rail is known in the industry as a thrie beam which has three crowns and is about a third wider than the conventional two crown guard rail. Usually a plurality of guard rails will be linked together horizontally at their distal ends, either end to end, or overlapping, and be supported by a plurality of vertically oriented posts which are typically “I-beamed” shaped, round, or square posts which are driven into the ground spaced apart a selected distance from the edge of the road. Of course, posts are also fabricated from aluminum, wood, or other metals and could be formed from polymers or fiberglass materials. The posts are usually driven into the ground and typically will yield under a desired amount of pressure and move within the ground or bend in accordance with the deformation of the guard rail rather than break off at ground level, in order to assist the rail in dissipating force upon receiving a blow from a vehicle. Typically a spacer block is disposed between the guard rail and the post to support the guard rail at a selected distance from the post to prevent an uncontrolled vehicle from hitting and entangling the posts. Thus, the spacer block keeps the automobile wheels from impacting the posts and initiating a roll of the vehicle. Moreover, the guard rail provides a continuous rail or track for guiding the vehicle providing at least some response time for the driver to regain control of the vehicle before leaving the roadway. The most popular material spacer blocks are made out of is wood. Some of the problem with wood is it deteriorates over time, it is heavy, it can give installers splinters, it contracts and expands with season changes. Also, wood tends to leach out chemicals typically used for pressure treating which may be toxic to the environment. Conventional plastic blocks on the market today are typically wood block designs made out of plastic. It typically requires two to three people to install a 12 foot section of guard railing to posts when using conventional spacer blocks, one to hold the guard rail and another to align and hold the spacer block in position with the post and a third person to insert bolts therethrough securing same. The instant invention provides a spacer block having improved strength, reduced weight, and competitive cost. Furthermore, the spacer block of the present invention was designed with the assembly process in mind in order to enable a single individual to erect a guard rail safety barrier system on spacer blocks supported by posts. SUMMARY OF THE INVENTION The guard rail support attachment and positioning block or spacer block is used to space guard railing away from posts such as “I” beams which are driven into the ground. The spacer block of the instant invention provides a design that is strong yet light, which makes it installation friendly, reduces the cost of manufacture, and permits one person to install a section of guardrail. In the past it might require two or three people to hold the rail and mount it to the spacer block and support post. Plastic properties are different from wood and requires a design that takes advantage of the different properties. The present design is specific for plastic, (polyethylene, PVC, polypropylene polyethylene terphthalate, nylon), or plastic/rubber and will out perform the wood design in all performance specifications. Moreover, the resiliency, elasticity, flexibility, and ability to be impervious to weathering elements, extend longtivity, and require little or no maintenance are important features of the present invention. A preferred embodiment to the spacer block of the instant invention is a generally rectangular block or cube including corded-out cavities to reduce weight and one or more tabs on the top and/or sides projecting outwardly for cooperatively engaging the sides and top edge of the post. A preferred embodiment is approximately 4 inches in width which is the same as conventional I-beam posts providing a lightweight, compact, high strength spacer block as compared to conventional spacer blocks made from wood or plastic typically having a width of 6 inches or more. A tab projecting outward from the face of the spacer block provides a support member to hold, steady, and even align the guard rail which rests thereon providing a means for one individual to mount the guard rail on spacer blocks, whereas conventional spacer blocks do not support the guard rail prior to attachment thereto and require at least two individuals if not three to attach the guard rail to the spacer block and post. The preferred embodiment of the spacer block of the present invention comprises one or more polymers, such as (polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, and mixtures thereof), and preferably a polymer/rubber blend. Other plastic materials which may be used may be selected from ABS, Acetyl, polypropylene oxide, nylon PBT, polycarbonate, polystyrene, modified polyphenylene oxide, polyester, fiberglass filled nylon, fiberglass filled styrene, fiberglass filled SAN, acrylic, ethylene copolymers, ionomers, and polysulfone. Of course the spacer block of the present invention may be formed of a single type of polymer or mixtures of various polymers. The polymers may be virgin material or the spacer block may be composed of at least some if not all of regrind materials, such as reground polyethylene, ethylene. The rubber and/or elastomeric compound which can be incorporated in the formulation may be comprised of a natural rubber or synthetic rubber, either virgin, regrind material or combinations thereof. It is contemplated that fiberglass may also be used as an additive or substitute raw material for all or at least a portion of the plastic material. Fillers such as wood chips. sawdust, calcium carbonate may also be used. The rubber from used tires have been a huge problem for the environment and could be utilized as the source of rubber for the instant invention. Moreover, the spacer blocks may themselves be recyclable. One preferred embodiment of the present invention is a spacer block utilizing a blend of at least one polymer including one or more of the plastic materials set forth heretofore, together with at least one rubber or elastomeric materials mixed and molded together with the polymer(s). The ability to mold large blocks of plastic containing virgin, and/or regrind thermoplastics which can be obtained from reusable containers, alone or together with virgin or grind rubber from used tires or other sources providing a useful means of disposal and recycling of waste products. One preferred embodiment of the invention utilizes grind rubber in combination with a one or more thermoplastics extruded or molded by low pressure injection molding or vacuum forming. The molding process is believed to encapsulate the rubber particles with the thermoplastic melt thereby providing a stronger blended product with enhanced performance capabilities as compared to a simple mixture of thermoplastic and rubber particles compressed together under high pressure. One source of the grind rubber is reground vehicle tires, representing a new method of disposal of used tires. Another important aspect of the present invention, is the molding of the spacer blocks using a structural foam process to further increase strength, reduce costs, and reduce the weight of the spacer blocks. The structural foam techniques utilizes a gas and/or chemical foaming agent injection process in the molding operation to form a foam core creating structural support webbing between solid plastic skins to increase structural strength and reduce weight and cost. The design of the block to include structural external webbing between void spaces in the spacer blocks of the instant invention further provides strength and weight advantages to the space block. The use of the blend of plastics and rubber and/or the webbing within the block cavity are unique features; however, in addition the utilization of structural foam forming the skin provides another novel feature not utilized in spacer blocks taught in the prior art. These embodiments of the present invention can be utilized with a spacer block molded having solid walls as well as a spacer block molded by structural foam whereby the walls are composed of an inner and outer skin with webbing thereinbetween. It is contemplated that all or at least a portion of the spacer block 10 could be filled with foam, gel, finely ground solid material, or even a liquid such as water and/or alcohol and water such as a glycol to inhibit freezing, or that the cavity could contain a bag containing same to cushion and absorb impact thereto. The material could be contained within the spacer block body or insertion of a container into the webbing or cavity formed within the spacer block could even be removable, such as a water bag or a deformable plastic container such as a jug. Moreover, a cellular core could be utilized for impact absorption within the cavities, or an impact absorbing block filled with cellular material, a gel, or a liquid could be disposed within the cavities formed in the present spacer blocks. Conventional spacer block assemblies require one person to hold the wood block while another holds the guardrail section and a third person installs the bolt, which holds the entire assembly together. The instant invention includes a hanger enabling the spacer block to hang on the I beam by itself. On the bottom of the spacer block is a guard rail resting tab so that the guard rail can be lifted and placed on the resting tab for mounting to the spacer block and post. One person can install a section by placing the bolt with in hands reach, it is possible for one person to lift a section of guardrail and rest it on the rail tab and install the bolt. A section of guardrail can be installed by a single person at a much faster pace than the designs of today. Therefor, it is an objective of the present invention to provide a spacer block which enables one person to mount a guard rail to a spacer block and post. It is another objective of the present invention to provide a spacer block which is splinter-less, has a longer life span than wood, lighter than wood. It is an object of the present invention to provide a plastic/rubber composite block which meets all required specifications set forth by the Federal Highway Administration. It is an object of the present invention to provide a spacer block which is environmentally friendly and be capable of being manufactured using recycled plastic, tires, and/or combinations thereof. It is an object of the present invention to provide a plastic/rubber composition which will out-last the wood blocks of today. It is an object of the present invention to provide a plastic-rubber composite spacer block that will meet or exceed the requirements of today's wooden block. Another important optional feature is the utilization of a plastic/rubber copolymer material to enhance the performance of the spacer block. Yet another object of the present invention is to provide an embodiment which may be formed from structural foam in order to optimize the weight to strength of the spacer block. Other objects, features, and advantages of the invention will be apparent with the following detailed description taken in conjunction with the accompanying drawings showing a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings in which like numerals refer to like parts throughout the several views and wherein: FIG. 1 is a perspective view showing the spacer block of the present invention mounted to a post and cooperatively engaging a guard rail; FIG. 2 is a rear perspective view showing the spacer block of FIG. 1 and the post; FIG. 3 is a rear perspective view showing the spacer block of FIG. 1 having a cavity formed between the top, side, and medial wall, and a cavity formed between the medial side, and bottom wall; FIG. 4 is a front perspective view of FIG. 1 showing the flat face of the spacer block and guard rail support and positioning tab; FIG. 5 is perspective rear view showing an alternate embodiment of the spacer block utilizing a plurality of tabs removably and slidably positional within grooves formed in the top surface of the spacer block; FIG. 6 is front view of an alternate embodiment of the spacer block showing webbing within the cavities; FIG. 7 is front view of an elongated embodiment of the spacer block utilizing the webbing arrangement of FIG. 6 for use with a thrie beam spacer block; FIG. 8 is front view of an alternate embodiment of the spacer block showing a different webbing arrangement within the cavities; FIG. 9 is a side view of the spacer block of FIG. 8 formed of structural foam; FIG. 10 is front view of an elongated embodiment of a spacer block utilizing the webbing arrangement of FIG. 8 for use with a thrie beam spacer block; FIG. 11 is a sectional view of a portion of a block showing a cellular core and an integral solid skin on each side thereof; FIG. 12 is a sectional view along Section 9—9 of FIG. 9 showing a structural foam segment showing a cellular core and an integral solid skin, wherein the transition from skin to core is gradual; FIG. 13 is a perspective view showing the spacer block of FIG. 12 mounted to a post and cooperatively engaging a guard rail; and FIG. 14 is a rear perspective view showing the spacer block of FIG. 12 and the post. DESCRIPTION OF THE PREFERRED EMBODIMENT The structural integrity of the various embodiments of the spacer blocks 10 of the present invention is attributed to the lightweight composite materials and the reinforcing webbing which provides the rigidity and controlled compression of the spacer blocks 10 under load. As illustrated in FIGS. 1 and 2, the spacer block 11 is mounted to a post 30, shown as an I-beam, and cooperatively engages and supports a guard rail 14 having an “M” shaped corrugated cross section. The spacer block 11 is shown with the removable slidable top tab 40 engaging the top edge of the I beam and the optional side tabs 42 preventing lateral movement thereof. The guard rail 14 is shown resting, positioned on the bottom tab 64 extending from the spacer block 11 supporting and aligning the guard rail 14 for attachment to the post 30 with one or more bolts extending through the through holes or bores 28 of the spacer block 11. Conventional I-beam posts 30 have a single hole punched into the flange 54 on one side of the post 30 only. As shown in FIGS. 1-5, the spacer block 10 used for conventional two crown guard rails or other conventional longitudinal rail members is typically about four (4) inches wide, about seven and one-half (7½) inches deep, and about 14 inches long. The spacer blocks 10 of the present invention include a front face 12 constituting the surface for attachment of the guard rail 14. The front face 12 is a generally flat solid surface. Of course it is anticipated that the face 12 could be webbed, curved, or even corrugated to correspond to the shape of the guard rail 14. The front face 12 can be formed to be concave and include a longitudinal depression to fit around posts as well. The front face 12 is connected to a rear face 16 by a pair of spaced apart opposing side walls 18 to a top panel 20 and a bottom panel 22. The interconnecting side walls 18, top panel 20, and bottom panel 22 may have rounded shoulders 24 as shown in FIGS. 1-4 or squared shoulders 26 as shown in FIG. 5. More particularly, the spacer block 11 can include a top cavity 34 and a bottom cavity 36 separated by a horizontally disposed medial wall 38 joining the front face 12 and rear face 16, defining a pair of sleeves having bores 18 therethrough. The corded-out cavities of the spacer block can be reinforced with webbing, solid block materials, gel material, foam, or liquids such as water, glycol, and mixtures thereof to aid in the dissipation of any stress. An important feature of a preferred embodiment of the spacer block 11 of the present invention is a pair of mounting bores 28 formed in the spacer block 11 oriented along the horizontal axis, side by side, to facilitate aligning a bore 28 of the spacer block 11 with the offset hole 55 preformed in the typical metal I-beam 30. The bore 28 can be positioned for quick alignment and attachment of the spacer block 11 and guard rail 16 to the post 30. More particularly, the spacer blocks 11 can include at least one and preferably a plurality of mounting bores 28 extending through the front face 12 for cooperative engagement of a corresponding bolt extending through the guard rail 14 and spacer block 11 for attachment to a post 30. In a preferred embodiment, the bore 28 extends through both the front face 12 and the rear face 16. Moreover, the bore 18 can extend through the medial wall 38 interconnecting the front face 12 and the rear face 16. It is contemplated that a sleeve 32 formed from a cylinder having a bore therethrough could be utilized as a removable spacer means for insertion between the hole formed in the front face 12 and rear face 16 abutting an interior surface of the front face 12, extending through the cavity formed in the interior of the block 11 to interconnect with the interior surface of the rear face 16 to provide additional structural support. A feature which is very useful and adaptable to the various spacer block 11 embodiments are locating and holding means for cooperatively engaging the post 30 and/or guard rail 14. The preferred embodiments of the spacer blocks 11 can include a top tab 40 fixedly attached to the top surface of the top panel 20. The tab 40 may also be provided as a removable or slidable tab having projections cooperatively engaging grooves formed in the channel 43 in a tongue and groove arrangement. The tabs 43 extend from past the rear face 22 of the spacer block for holding the spacer block 11 onto the top of a post 30. It is contemplated the tab 40 could comprise a flat plate or even a ring to engage a cylindrical post; however, the embodiment shown in FIGS. 1-5 includes projecting members or fingers 50 extending downward from the tab 40 mounted on the top of the block 11 extending past the rear face 22 enabling the tab 40 to set on top of an I-beam shaped post 30 with the fingers 50 extending behind the flanges 54 of the post 30 thereby holding the spacer block 11 securely to the post 30 for mounting. Moreover, As shown in FIGS. 1-4 a groove or channel 43 can be formed or cut into the surface of the spacer block 11 top panel 20 to facilitate molding or handling of the blocks. As shown in the drawings, a leg 48 can extend from the bottom surface of the tab 40 to be supported by and preferably to connect with the top of the channel 43 in order to provide additional structural support for the tab 40. As shown in FIG. 5, a first and second channel, 56 and 58 respectively, are formed in the top panel 20 of the spacer block 13. A pair of tabs 41 and 46 fixedly attached to the top surface of the top panel 20 extend past the rear face 22 of the spacer block for holding the spacer block 13 onto the top of a post 30. The tabs 41 and 46 may also be provided as a removable or slidable tab having projections cooperatively engaging grooves formed in the channels 56 and 58 in a tongue and groove arrangement. The tabs 41 and 46 extend from past the rear face 22 of the spacer block 13 for holding the spacer block 13 onto the top of a post 30. Thus, the top tab 42 allows the spacer blocks 13 to hang on the post 30 during mounting of the guard rail, post, and spacer block assembly. A stop means may be incorporated within the channel or attached to the ends thereof to limit movement of a movable top tab 40, 41, and 46. As shown in FIGS. 1-5, one or more optional side tabs 42 can be utilized with the spacer blocks 10 of the present invention for cooperatively engaging the post 30. FIGS. 6-14 show the use of side flanges 45. The side tabs 44 or side flanges 45 are spaced apart generally opposing one another and preferably in alignment with one another; however, it is not necessary that the side tabs 44 align with one another or that there be a corresponding number of side tabs on each side. Even one side tab 44 or side flange 45 aids in positioning the spacer blocks 10 with respect to the post 30. The side tabs 44 or side flanges 45 can be integrally formed within the spacer block 10 or attached by holding means such as a screw or projection engaging a hole formed in the spacer block 10. The spacer block 10 can be aligned in proper orientation by utilizing the side tabs 42 extending from the sides of the block 10. A support tab 64 can be provided extending from the bottom panel 22 of the front face 12 for supporting a guard rail 14 resting thereon and aiding in the alignment of the bores 28 with holes in the guard rail 14 and post 30. A recess or notch 60 can be formed or cut into the bottom edge panel 22 and rear face 16 of the spacer block 10 disposed therein for cooperatively engaging the support tab 64 permitting stacking and nesting of the spacer blocks 10 one upon the other for storage or transport. The spacer blocks 10 of the present invention can be molded into specific embodiments maximizing structural integrity while maintaining controlled flexibility via reinforcing webbing and selecting particular rubber and thermoplastic compositions. FIGS. 6 and 8 show alternate embodiments of the spacer block of the present invention which utilize webbing within the top cavity 34 and bottom cavity 36 separated by a horizontally disposed medial wall 38 joining the front face 12 and rear face 16, defining a pair of sleeves formed as cylinders having bores 18 therethrough. A preferred configuration of webbing design is shown in FIGS. 6 and 8, wherein the rear end of the spacer block shows webbing formed by various lengths of lateral, longitudinal, and transverse members having cavities thereinbetween are formed to increase the structural strength while controlling compression and flexing forces and minimizing the weight of the spacer block. As shown in FIG. 6, a spacer block 70 includes webbing which extends from the interior surface of the front face 12 through the cavity 34 or 36 having a distal end equal distance with the side walls 18 forming the rear face 16. Extending from the center of the interior surface of the front face 12 and through the first cavity 34 is a first cylindrical reinforcement member 72. A corresponding second cylindrical reinforcement member 74 extends from the interior surface of the front face 12 through the second cavity 36. In each cavity 34 and 36 respectively, the webbing comprises runners extending radially from a cylindrical reinforcing members 72, 74 to intersect with the interior surface of either the side wall 18, top panel 20, bottom panel 22, or medial wall 38. As shown in FIG. 6, within the first cavity 34 a first runner 76 extends vertically from the top panel 20 to intersect with the cylindrical reinforcing member 72. A pair of second runners 78 extend radially from the cylindrical reinforcing member 72 toward the corners connecting the top panel 20 with the side wall 18. A pair of third runners 80 radiate horizontally from the cylindrical reinforcing member 72 toward the side walls 18. A fourth pair of runners 82 radiate downwardly from the cylindrical reinforcing member 72 toward the bores 28 in the medial wall 38 forming a tear drop shaped cavity thereinbetween. Within the second cavity 36 of the spacer block 70 a first runner 176 extends vertically from the bottom panel 22 to intersect with the cylindrical reinforcing member 74. A pair of second runners 178 extend radially from the cylindrica reinforcing member 74 toward the corners connecting the top panel 20 with the side wall 18. A pair of third runners 180 radiate horizontally from the cylindrical reinforcing member 74 toward the side walls 18. A fourth pair of runners 182 radiate downwardly from the cylindrical reinforcing member 172 toward the bores 28 in the medial wall 38 forming a tear drop shaped cavity thereinbetween. Moreover, spacer block 70 can be formed or molded having a front face 12 which is slightly shorter than the rear face 16 so that the top panel 12 or bottom panel 22 incline toward one another slightly at the front face 12 to facilitate removing the spacer block from the mold. The notch (not shown) of the spacer block 70 is formed on the bottom of the bottom panel as a declining channel extending from the rear face 16 toward the front face 12 which does not extend through the interior surface of the bottom panel 22. FIG. 7 shows an alternate elongated embodiment of a spacer block 84 for use with thrie beam guard rails. The elongated spacer block 84 includes an additional third center cavity 35, medial wall 138 and bores 128, disposed between the first top cavity 34 and the second bottom cavity 36. The spacer block 84 utilizes substantially the same webbing configuration of the spacer block 70 of FIG. 6. The spacer block 84 is approximately 4 inches wide, about 21 inches long, and about 7½ to 8 inches thick. Of course, the depth and length dimension could vary on any of the spacer blocks 10 depending upon the dimensions of the selected guard rail; however, the four inch wide dimension, although not critical is preferably maintained at about 4 inches or equivalent to the thickness of the mounting post excluding the side rails 45 or side tabs 42. Within the third center cavity 35 of the spacer block 84 is a pair of runners 278 radiating upwardly from the cylindrical reinforcing member 172 toward the bores 28 in the medial wall 38 forming a tear drop shaped cavity thereinbetween. A pair of runners 280 radiate horizontally from the cylindrical reinforcing member 274 toward the side walls 18. A pair of runners 282 radiate downwardly from the cylindrical reinforcing member 274 toward the bores 128 in the medial wall 138 forming a tear drop shaped cavity thereinbetween. The spacer block embodiment 86 has similar dimensions, features, and webbing to that of the spacer block 84. As best illustrated in FIGS. 8 and 9, it differs from spacer block 84 in that spacer block 86 does not utilize runner 76 extending vertically from the top panel 20 to intersect with the cylindrical reinforcing member 74 or the vertical runner 176 extending vertically from the bottom panel 22 to intersect with the cylindrical reinforcing member 74. Moreover, the notch 260 is formed or cut into the bottom edge panel 22 and rear face 16 of the spacer block 10 forming a pocket, and does not cut through the bottom panel 22 exterior surface. FIG. 10 shows an alternate elongated embodiment of the spacer block 86 for use with thrie beam guard rails. The elongated spacer block 88 includes an additional third center cavity 35, medial wall 138 and bores 128, disposed between the first top cavity 34 and the second bottom cavity 36. The spacer block 88 utilizes substantially the same webbing configuration of the spacer block 86 of FIG. 8. The spacer block 88 is approximately 4 inches wide, about 21 inches long, and about 7½ to 8 inches thick. Of course, the depth and length dimension could vary on any of the spacer blocks 10 depending upon the dimensions of the selected guard rail; however, the four inch wide dimension, although not critical is preferably maintained at about 4 inches or equivalent to the thickness of the mounting post excluding the side rails 45 or side tabs 42. Structural Foam Spacer Blocks The structural foam spacer blocks of the present invention are molded and have a cellular core and an integral solid skin, wherein the transition from skin to core is gradual as shown in FIG. 11. The solid skin gives the molded part its form and toughness, while the cellular core contributes to the high strength to weight characteristics. The skin of the structural foam spacer blocks can be up to ½ inch thick, more preferably up to ¼ inch thick and most preferably up to ⅛ inch thick. There are two basic types of plastics available for foaming. Thermoset materials such as polyurethane is produced by polyaddition of reactive components such as polyol and isocyanate. The exotherm generated by the reaction vaporizes a blowing agent that causes the mixture to expand. Thermoplastic materials typically require the addition of physical or chemical blowing agents to product a foam and do not undergo chemical change. Some blowing agents decompsoe when heated to process temperature to evolve a gas such as carbon dioxide. Often sodium bicarbonate or ammonium carbonate is used for cellular or sponge rubber, halocarbons and methylene chloride is used in urethane, pentane in expanded polystyrene, and in some cases hydrazine for foamed plastics. Spacer blocks utilizing plastic and/or rubber components formed with solid walls usually does not exceed 4 mm (0.16 inches). The wall thickness of the spacer block composed of plastic and/or rubber components is usually not less than about 4 mm in order to gain the full advantage of the foam webbing structure between the two layers of skin. Thus, thick wall thicknesses may be obtained using structural foam. Moreover, structural foam spacer blocks have few if any sink marks due to the residual gas pressure in the cells, which allows the material to expand internally while the part cools, thus holding the skin firmly against the mold walls. Because of their cellular structure the spacer blocks formed of structural foam are virtually stress-free, resulting in bowing and warpage being greatly reduced. Because of its cellular structure, less resin is used to make it resulting in a part 3 to 4 times more rigid than the solid part of the same weight. This enables the instant invention to be made of commodity plastics such as polystyrene and polyethylene with or without rubber in a load bearing application. The properties of the structural form spacer block depends on the base polymer, overall part density, density distribution, skin thickness, cell shape and size. All of these parameters are affected by the processing method, process variables, wall thickness, and mold design. Density of the structural foam varies across the cross section and is lowest in the core. As the distance from the center of the foamed block increases, the cells get smaller until they disappear completely in the outer skin. The objective is to produce a part with high skin density and very low core density without the presence of voids. The range of the density varies in the present invention from about 30 percent in the center to 100 percent at the outer skin. Moreover, the overall part density, density distribution, skin thickness, cell shape and size depend upon the mold cycle which may vary between ½ to 10 minutes. A preferred embodiment of the spacer block of the instant invention is processed using a low pressure injection molding machine using thermoplastics and/or rubber. A screw is used to plasticate a mixture of polymer and chemical blowing agent of up to 1% and preferably up to ½ percent wherein the screw barrels has zones at different temperatures arranged so that the blowing agent in only near the nozzle. A foamable mixture is produced and pumped under pressure to an accumulator an stored in a molten state at a pressure higher than the foaming pressure. Upon opening a valve in the nozzle, a portion of the foamable mixture is discharged from the accumulator into the mold. The mold cavity is filled by the gases generated by the decomposition of the chemical blowing agent forcing the material into the shape of the mold. The pressure and temperature of the material in the mold drop resulting in bubbles developing in the core. In a preferred embodiment, the melt is charged at about 400° F. and the melt temperature is between about 380° to 450° F. It should be noted that the structural foam blocks 10 of the present invention can be made utilizing of a rubber compound in combination with a plastic. The plastic tends to encapsulate the rubber particles and act as a binder. The rubber produces enough gas during processing under the heat and pressure of the low pressure injection molding process that the structural foam product can be made without the addition of any type of chemical blowing agent. The spacer block of the present invention may be formed by injection molding, and preferably low pressure injection molding such as is used for structural foam products. The spacer block can be comprised of a virgin or regrind plastic or combinations thereof without any rubber. The plastic may be selected from the following polymers: polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, ABS, Acetyl, polypropylene oxide, nylon, PBT, polycarbonate, polystyrene, modified polyphenylene oxide, polyester, fiberglass filled nylon, fiberglass filled styrene, fiberglass filled SAN, acrylic, ethylene copolymers, ionomers, and polysulfone. Of course the spacer block of the present invention may be formed of a single type of polymer or mixtures of various polymers. Typically a chemical blowing agent in an amount of less than 5 percent, and more preferably in an amount of less than 1 percent and most preferably in amount of less than ½ percent can be used with the 100% polymer composition spacer blocks 10. A rubber and/or elastomeric compound can be incorporated in the formulation as a substitution for up to at 70 percent, and more preferably at less than 50% and most preferably from about 40 to 50 percent depending upon the strength to weight ratio desired and the structural properties required for a particular application or size of guard rail. Regrind rubber is typically less expensive than plastic materials therefor, as much as 40 to 50 percent rubber may be used in spacer blocks for normal impact applications or posts spaced closed together, whereas a composition with less than 45 percent rubber may be desired for applications requiring the posts to be spread further apart from one another. The type of rubber is also an important consideration in that the rubber may be comprised of a natural rubber or synthetic rubber, either virgin, regrind material or combinations thereof. Additives such as fillers and fiberglass may further reduce the cost of manufacture and provide the requisite strength. Moreover, because of the gases produced from injection molding the rubber particles, the use of a chemical blowing agent is an option and is not required when processing the plastic and rubber mixed compositions. A particular preferred embodiment comprises polyethylene together with grind rubber ranging in an amount of up to 45 percent. Yet another more preferred embodiment utilizes from about 30 to 45 percent regrind rubber and utilizes ethylene as the binding polymer. Another preferred embodiment utilizes a powdered processing aid from Polymer Process Technologies, Inc. in Akron, Ohio referred to by the trademark PPT-SYS, (PPT-SYS(R) for rubber applications and PPT-SYS(P) for plastic applications), having a specific gravity of about 1.01, pH of about 7, melting point range of over 600° F. which is a highly effective alloying agent for compatibilizing and alloying cured rubber, virgin or regrind, with plastic powder to form compounds having little or no change in physical properties. Moreover, another preferred embodiment may contain a nontoxic blend of naturally occurring materials, (plant polymers, gums, and anionic salts), marketed by Polymer process Technologies, Inc, under the trademark of PPT-RNU that when added to post consumer plastics of all kinds, will repair heat history plastics to near virgin polymer condition. in addition to or instead of the PPT-SYS (R)/(P). The material has a pH of about 6.8, a specific gravity of about 1.05, a melt point flow of over 650° F. and used in amounts of up to 10% by weight and more preferably from about 3 to about 6% by weight. Another preferred embodiment utilizes both the PPT-RNU and PPT-SYS additives with rubber and a polymer such as polyethylene to enhance the compatibility and performance of regrind rubber from tires being compounded with virgin or recycled polymers such as polyethylene in conventional compounding equipment at processing temperatures of from about 360° to 410° F. which is typical for extrusion and compounding operations. The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom, for modification will become obvious to those skilled in the art upon reading this disclosure and may be made upon departing from the spirit of the invention and scope of the appended claims. Accordingly, this invention is not intended to be limited by the specific exemplifications presented hereinabove. Rather, what is intended to be covered is within the spirit and scope of the appended claims.

Claims (15)

I claim: 1. A spacer block for attaching a guard rail to a post, comprising: a pair of spaced apart opposing side walls having respective first ends and second ends; a top panel disposed proximate said first end of said side walls; a bottom panel disposed proximate said second end of said side walls; said top panel said bottom panel and side walls forming a generally rectangular block having a first front face and a second rear face; an engagement mechanism operably coupled proximate said top panel, said engagement mechanism operable to engage said block with said post, the engagement mechanism including a tab operably coupled to the top panel, the tab extending beyond the second face of the spacer block, at least two spaced apart fingers operably coupled proximate a distal end of the tab, the fingers extending from a bottom surface of the tab and forming a gap between the fingers and the second face of the spacer block, the gap between the fingers operable to engage respective sides of a web on an I-beam support post and the gap between the fingers and the second face of the spacer block operable to engage respective sides of a flange on the I-beam support post; resting mechanism operably coupled proximate said bottom panel for supporting a bottom edge of a guard rail thereon; at least one mounting bore extending there through from said first front face to said second rear face; and an alignment mechanism operably coupled to at least one side wall. 2. The spacer block of claim 1 comprising a thermoplastic polymer and a rubber material. 3. The spacer block of claim 1, comprising a structural foam thermoplastic composition. 4. The spacer block of claim 1, comprising a structural foam thermoplastic and rubber composition. 5. The spacer block of claim 1, further comprising: a medial wall disposed between the side walls, the medial wall positioned generally perpendicular to the side walls and generally parallel to the top and bottom panels; the medial wall, top panel and side walls forming a first cavity; and the medial wall, bottom panel and side walls forming second cavity. 6. The spacer block of claim 5 further comprising: at least one mounting bore traveling through the medial wall from the first face of the spacer block to the second face of the spacer block; and the mounting bore operable to align with at least one mounting aperture on the support post. 7. The spacer block of claim 5 further comprising a reinforcement structure disposed in at least one of the cavities. 8. The spacer block of claim 5 further comprising a webbing structure disposed within at least one of the cavities, the webbing structure operable to structurally reinforce the spacer block. 9. The spacer block of claim 1 further comprising: at least one mounting bore disposed in the first medial wall, the mounting bore traveling between the first and second faces of the spacer block; and at least one mounting bore disposed in a second medial wall, the mounting bore traveling between the first and second faces of the spacer block. 10. The spacer block of claim 1 further comprising: said resting mechanism including a tab disposed proximate the bottom panel, said tab extending from the first face of the spacer block. 11. The spacer block of claim 1 wherein said alignment mechanism operably coupled to at least one side wall is at least one tab projecting past said rear face for cooperatively engaging said post. 12. The spacer block of claim 1 further comprising the first face including a generally flat solid surface. 13. The spacer block of claim 1 further comprising the bottom panel including a notch disposed proximate the second face of said spacer block, said notch operable to allow stacking of said spacer blocks. 14. The spacer block of claim 1 wherein said spacer block is formed using an injection molding process. 15. The spacer block of claim 1 wherein the spacer block is formed at least in part, using a structural foam. US10/001,903 -11-15 -11-15 Guard rail support, attachment, and positioning spacer block Expired - Lifetime USB2 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title US10/001,903 USB2 (en) -11-15 -11-15 Guard rail support, attachment, and positioning spacer block US10/079,280 USB2 (en) -11-15 -02-20 Guardrail support, attachment, and positioning block US10/385,006 USA1 (en) -11-15 -03-10 Guardrail support, attachment, and positioning block US10/885,398 USA1 (en) -11-15 -07-06 Guard rail support, attachment, and positioning spacer block

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title USP -11-15 -11-15 US10/001,903 USB2 (en) -11-15 -11-15 Guard rail support, attachment, and positioning spacer block

Related Child Applications (3)

Application Number Title Priority Date Filing Date US10/079,280 Continuation-In-Part USB2 (en) -11-15 -02-20 Guardrail support, attachment, and positioning block US10/385,006 Continuation-In-Part USA1 (en) -11-15 -03-10 Guardrail support, attachment, and positioning block US10/885,398 Continuation USA1 (en) -11-15 -07-06 Guard rail support, attachment, and positioning spacer block

Publications (2)

Publication Number Publication Date USA1 USA1 (en) -07-18 USB2 true USB2 (en) -07-06

Family

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Family Applications (2)

Application Number Title Priority Date Filing Date US10/001,903 Expired - Lifetime USB2 (en) -11-15 -11-15 Guard rail support, attachment, and positioning spacer block US10/885,398 Abandoned USA1 (en) -11-15 -07-06 Guard rail support, attachment, and positioning spacer block

Family Applications After (1)

Application Number Title Priority Date Filing Date US10/885,398 Abandoned USA1 (en) -11-15 -07-06 Guard rail support, attachment, and positioning spacer block

Country Status (5)

Country Link US (2) USB2 (en) AU (1) AUA1 (en) CA (1) CAC (en) MX (1) MXPAA (en) WO (1) WOA2 (en)

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* Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title USA1 (en) * -11-26 -05-27 Brown David Todd System for a sliding door with a camber USA1 (en) * -11-26 -05-27 Brown David Todd System for a sliding door with a spacer block USA1 (en) * -11-26 -01-11 Tci Supply, Inc. System for a sliding door with a camber USB2 (en) -11-26 -08-15 Tci Supply, Inc. System for a sliding door with a camber USB2 (en) -11-26 -03-18 Tci Supply, Inc. System for a sliding door with a camber USB2 (en) * -01-06 -01-08 Beeche Gregory L Structural member and modular beam system USA1 (en) * -01-06 -07-08 Beeche Gregory L. Structural member and modular beam system USB2 (en) -08-12 -08-08 Sci Products Inc. Crash attenuator with cable and cylinder arrangement for decelerating vehicles USB2 (en) -08-12 -11-08 Sci Products Inc. Crash attenuator with cable and cylinder arrangement for decelerating vehicles USB2 (en) * -08-12 -03-28 Sci Products Inc. Side panel USA1 (en) * -08-12 -11-03 Sci Products Inc. Crash attenuator with cable and cylinder arrangement for decelerating vehicles USA1 (en) * -08-12 -03-03 Sci Products Inc. Side panel USA1 (en) * -08-12 -02-17 Smith Jeffery D. Crash attenuator with cable and cylinder arrangement for decelerating vehicles USA1 (en) * -09-10 -09-08 P.V. Vijay Blocks for absorption of collision energy USA1 (en) * -06-10 -12-15 Monroeville Industrial Moldings, Inc. Guardrail support members USB2 (en) -06-10 -06-09 Monroeville Industrial Moldings, Inc. Guardrail support members USB2 (en) -06-10 -01-20 Monroeville Industrial Moldings, Inc. Guardrail support members USA1 (en) * -07-06 -11-27 K.E.S.S., Inc. Guardrail support, attachment, and positioning block USB2 (en) * -07-06 -09-21 K.E.S.S., Inc. Guardrail support, attachment, and positioning block USB2 (en) * -07-06 -07-14 K.E.S.S. Inc. Guardrail support, attachment, and positioning block USB2 (en) -07-06 -12-15 Dennis Raymond Prout Spacing device USB2 (en) -07-06 -11-16 K.E.S.S. Inc. Guard rail mounting block and guard rail system incorporating the same USA1 (en) * -07-06 -06-12 Dennis Raymond Prout Spacing Device USA1 (en) * -07-06 -06-26 King David T Guardrail support, attachment, and positioning block USA1 (en) * -07-06 -10-30 King David T Guard rail mounting block and guard rail system incorporating the same USB2 (en) -07-19 -02-01 Carl M. Ochoa Releasable highway safety structures USA1 (en) * -07-19 -08-06 Ochoa Carl M Releasable Highway Safety Structures USA1 (en) * -07-19 -04-10 Ochoa Carlos M Posts and release mechanism for highway safety structures USB2 (en) -07-19 -05-12 Ochoa Carlos M Releasable highway safety structures USA1 (en) * -07-19 -01-19 Ochoa Carlos M Releasable highway safety structures USDS1 (en) * -01-04 -03-07 Monroeville Industrial Moldings, Inc. Support block with long wings USB1 (en) * -03-08 -05-27 Houseman Eric M Picket fence building guide USA1 (en) * -09-19 -03-22 Alberson Dean C A weakened guardrail mounting connection USA1 (en) * -09-19 -03-22 Alberson Dean C Yielding post guardrail safety system USA1 (en) * -09-19 -03-22 Alberson Dean C Guardrail flange protector USA1 (en) * -03-01 -09-20 Alberson Dean C Yielding post guardrail safety system incorporating thrie beam guardrail elements USB2 (en) -03-01 -08-06 The Texas A&M University System Yielding post guardrail safety system incorporating thrie beam guardrail elements USB2 (en) -08-21 -02-01 Nucor Corporation Roadway guardrail system USB2 (en) -08-21 -08-19 Nucor Corporation Roadway guardrail system USB2 (en) -08-21 -01-09 Nucor Corporation Roadway guardrail system USA1 (en) * -08-21 -02-26 Nucor Corporation Roadway guardrail system USA1 (en) * -08-21 -02-26 Nucor Corporation Roadway guardrail system USB2 (en) -08-21 -01-15 Nucor Corporation Roadway guardrail system USB2 (en) -02-08 -08-21 Nucor Corporation Cable guardrail system and hanger USA1 (en) * -02-08 -09-03 Nucor Corporation Cable guardrail system and hanger USA1 (en) * -11-12 -05-13 Bww Enterprises, Inc. Guardrail block and reflector system USB2 (en) -11-12 -12-14 Bww Enterprises, Inc. Guardrail block and reflector system USB2 (en) * -06-15 -02-12 Eric J. Christ Anti-tipping die tool holder USA1 (en) * -06-15 -12-16 Middle Atlantic Products, Inc. Anti-tipping die tool holder USB2 (en) -08-26 -08-02 The Texas A&M University System Module for use in a crash barrier and crash barrier USB2 (en) -08-26 -12-27 The Texas A&M University System Methods for the manufacture of a module for use in a crash barrier and assembly of the crash barrier USB2 (en) -06-11 -04-19 Gary L. Reinert, Sr. One-piece metal plate foundation with integral offset plate for guardrails and other structures and guardrail system utilizing same

Also Published As

Publication number Publication date MXPAA (en) -02-14 WOA9 (en) -05-06 AUA1 (en) -05-27 CAA1 (en) -05-23 WOA2 (en) -05-23 USA1 (en) -11-25 CAC (en) -04-07 USA1 (en) -07-18 WOA3 (en) -09-12

Legal Events

Date Code Title Description

606.1 Guardrail - Engineering Policy Guide

606.1.1 Types of Guardrail

31 in. Midwest Guardrail System

MGS Guardrail 6 ft. Posts - single W beam rail with 6 ft. 3 in. post spacing.

MGS Guardrail 8 ft. Posts - single W beam rail with 6 ft. 3 in. post spacing.

MGS Double Faced Guardrail - double W beam rail (single beam on each side of post) with 6 ft. 3in. post spacing, generally for use in median.

MGS Guardrail 6 ft. Post, 3 ft. 1-½ in. spacing - single W beam rail with 3 ft. 1-1/2 in. post spacing.

MGS Guardrail 6 ft. Post, 1 ft. 6-¾ in. spacing - single W beam rail with 1 ft. 6-3/4 in. post spacing.

MGS Long Span 6 ft. Posts – a single W beam rail system with modifications to omit certain posts at drainage culverts and small bridges.

29 in. NCHRP 350 Guardrail System

Type A Guardrail - single W beam rail with 6 ft. 3 in. post spacing.

Type B Guardrail - double W beam rail (single beam on each side of post) with 6 ft. 3in. post spacing, generally for use in median.

Type D Guardrail - single W beam rail with 12 ft. 6 in. post spacing for use at end of road or street.

Type E Guardrail - single thrie beam rail with 3 ft. 1-½ in. post spacing.

606.1.2 Guardrail Terms

Blockout – a spacer block to separate the guardrail beam from the post used on most types of guardrail.

If you want to learn more, please visit our website DACHU.

Bullnose Guardrail System – an enclosed guardrail design that wraps a semi-rigid guardrail around a hazard.

End Anchor - a guardrail end device without a buffer end to develop the full strength of the rail system.

Embedded End Anchor - an end anchorage system for guardrail whereby the rail is embedded in a concrete block and buried in the backslope.

MASH – AASHTO Manual for Assessing Safety Hardware (), or newer.

MASH End Terminal – Crashworthy End Terminals that have been approved using the MASH testing requirements.

MGS Guardrail – Midwest Guardrail System (MGS) a non-proprietary MASH approved guardrail system.

Non-350 Guardrail - Existing guardrail that does not meet NCHRP 350 testing requirements. Existing Type A guardrail that is either less than 27 ¾ in. tall, uses steel blockouts, or uses blockouts that are less than 8 in. deep is considered to be Non-350 Guardrail.

Pre-350 End Terminal – Devices that have not been approved by NCHRP 350 test requirements. Examples include Breakaway Cable Terminals (BCT), MELT, Turn-down ends, concrete height transitions and any unprotected blunt ends.

Rock Face End Anchor - an end anchorage system for guardrail whereby the rail is bolted to a rock face.

Figures Warrant for Median Barriers Videos These are very short video clips of guardrail crash tests conducted at the Midwest Roadside Safety Facility in Lincoln, Nebraska. The video image is very small (and typically located on the lower left of your screen) unless you click the video's enlarge button. A successful pickup test A successful pickup test, slow motion Another successful pickup test Another successful pickup test, rear view A successful car test An unsuccessful pickup test MoDOT cooperates with other states in the Midwest State's Regional Pooled Fund Program to develop and improve new and innovative safety devices.

606.1.3 Guardrail Systems

Beam guardrail systems are shown in Std. Plan 606.00 and other standard plans. Strong post W-beam guardrail (MGS, Type A and Type B) and thrie beam guardrail (Type E) are semirigid barriers used predominantly on roadsides. Installed correctly, W-beam laps the rail splices in the direction of the traffic flow, crashworthy end terminals are used and the rail is blocked away from the strong posts. Placement of curb at guardrail installations also requires careful consideration.

The Midwest Guardrail System (MGS) is mounted at a 31 in. rail height, requires blockouts that are 12 in. deep (measured from the rail to the post) and includes rail elements that are spliced between guardrail posts.

The MGS offers tolerance for future resurfacings. The MGS allows a 3 in. height tolerance from 31 in. to 28 in. without adjustment of the rail element.

606.1.3.1 Guardrail Selection and Placement

During the project development process, use the following guidance to determine the guardrail improvements for the project:

Use MGS for new runs of guardrail on all routes. When guardrail is installed along existing shoulders that are 4 ft. or wider, the shoulder width may be reduced by 4 in. to accommodate the 12 in. blockout. For shoulders narrower than 4 ft., long post MGS should be considered.

On major routes with existing guardrail height at or higher than 27 ¾ in., the guardrail may be used in place.

On major routes with existing guardrail height lower than 27 ¾ in., replace the run with MGS.

For existing guardrail height lower than 27 ¾ in. within the limit of ramps, replace the run with MGS.
Improvements to existing guardrail that extends beyond the limits of the ramp onto the crossing route will be a judgment of the engineer of record.

On minor routes, existing runs of rail, in serviceable condition, may be left in place. Engineering judgment in accordance with AASHTO’s Roadside Design Guide and crash history should be used to evaluate guardrail needs for each project. Where future overlays are anticipated within the next ten years, use of MGS should be considered.

On minor routes where any portion of the guardrail run is repaired, moved or modified in any way, the following options are available based upon the height of rail:

For existing runs with a rail height lower than 24 ¾ in., replace the run with MGS.
For existing runs in serviceable condition with a rail height lower than 27 ¾ in. but as high or higher than 24 ¾ in., adjust the height to a minimum height of 27 ¾ in. or replace the run with MGS at 31 inches.
Existing runs with rail height of 27 ¾ in. or greater can be used in place.

When it is necessary to replace more than 50% of an existing length of guardrail as a result of slides or extensive damage, the entire length of guardrail is to be removed and replaced with MGS at 31 inches.

Some 31 in. proprietary guardrail systems that do not incorporate the use of blockouts have been successfully crash-tested for MASH . The use of this type of system may be appropriate for some applications. Contact the Design Division for further details.

Criteria for guardrail use on outer roadways are the same as for other roads except for the shoulder side adjacent to a through lane. Guardrail is specified along outer roadways where the outer roadway is 10 ft. or more above the main roadway, and the shoulder of the outer roadway is less than 25 ft. from the top of the roadway backslope. Sometimes it is more economical to move the outer roadway back sufficiently to eliminate the requirement for guardrail. Guardrail along outer roadways is installed with the face of the rail toward the outer roadway. Double faced MGS may be required if the guardrail is within the limits of the clear zone for the through lanes.

Additional Guidance

The slope of the area between the edge of the shoulder and the face of the guardrail must be 1V:10H (10:1) or flatter. Do not place guardrail on a fill slope steeper than 1V:6H (6:1).

Shoulder cross slope may be adjusted during resurfacing in an attempt to use in place existing guardrail (in serviceable condition) that meets current design guidelines. The accepted range in cross-slope for shoulders is 2% to 6%. A tapered shoulder resurfacing to a minimum ½ in. thickness may be considered. A maximum of 8% algebraic difference in the slope of pavement and shoulder at the pavement edge is permitted. If the shoulder surfacing cannot be tapered to minimum thickness without exceeding the maximum cross slope, the shoulder resurfacing will be constructed to the minimum cross slope of 2% and the existing guardrail will be replaced with MGS at 31 inches.

On the high side of superelevated sections, place guardrail at the edge of shoulder prior to the slope break.

For guardrail installed at or near the shoulder, 2 ft. of shoulder widening behind the guardrail posts must be provided from the back of the post to the beginning of a fill slope. On existing roadways with less than 2 ft. behind the guardrail, Class III shaping slopes shall be used to widen the shoulder.

On projects where no roadway widening is proposed and the minimum 2 ft. shoulder widening behind the barrier is not practicable, the 8 ft. MGS long post design should be used. A cost analysis should be conducted to determine whether to add the 2 ft. shoulder widening or use 8 ft. MGS long post design. For fill slopes steeper than 1V:2H (2:1), the use of special designs are necessary. Contact the Design Division for further details.

MASH end terminals at 31 in. height will require a height and lateral transition for connection to existing non-MGS guardrail. The plans will need to include a 25 ft. MGS Transition Section between the MASH end terminal and the existing or modified guardrail.

Adjustment of guardrail height should be performed in accordance with the guidance provided in the Assessment of Existing G4(1S) Strong Post Guardrail (Rail). The minimum guardrail height after adjusting/replacing blocks is 27 ¾ inches. If the 27 ¾ in. height will not be achieved, the guardrail must be replaced with MGS. A non-standard job special provision for height adjustment is available.

In areas of a roadway cut section, or where the road is transitioning from cut to fill, designers may consider the application of an embedded terminal. Often this can be accomplished by extending the guardrail beyond the length of need to tie the guardrail into the backslope. When properly designed and located, this type of anchor provides full shielding for the identified hazard, eliminates the possibility of an end-on impact with the terminal, and minimizes the likelihood of the vehicle passing behind the rail.

Any unconnected or unacceptably connected bridge approach guardrail is to be connected to the bridge by an acceptable transition design.

The use of curb in conjunction with guardrail is discouraged. When used in conjunction with MGS, an acceptable option is to place up to a 6 in. high curb at a maximum 6 in. offset outside the face of the rail at any posted speed. Where barrier curb is used, guardrail is placed with the guardrail face located at the face of the curb and the top of the rail is located 31 in. above the pavement elevation at the curb face. Where mountable curb is used, guardrail is placed with the face at the edge of the usable shoulder and the top of the rail is located 31 in. above the shoulder elevation. Where curb and gutter is used, guardrail is placed with the guardrail face at the face of curb and the top of the rail at 31 in. above the gutter flow line.

When an obstacle such as a culvert headwall is located close to the shoulder line, the MGS long-span section can be used to span up to 25 feet. When obstacles are to be marked with a Type 3 Object Marker, it shall be in accordance with EPG 903.17.4 Object Markers for Obstructions Adjacent to the Roadway.

Guardrail should be used to protect traffic from non-breakaway signposts, sign trusses and bridge piers within the clear zone. Typical treatments are indicated in the standard plans. Bridge piers located close to the roadway are marked with a Type 2 Object Marker.

Guardrail is usually galvanized and has a silver color. It can also be provided in weathering steel that has a brown or rust color. Along Scenic Byways, at scenic overlooks, state highways through national forests, or other designated areas where aesthetic guardrail is needed, consider using weathering steel guardrail, colored terminals (powder-coated galvanized steel), colored steel posts (galvanized weathering steel or powder-coated galvanized steel) or wood posts to minimize the barrier’s visual impact. Funding for the increased cost of aesthetic guardrail should come from the local public agency or other outside sources. If a specific appearance is deemed appropriate in order to coordinate with existing facilities or some other aspect of the scenic location, the designer is to specify the system desired with a job special provision.

Guardrail details and typical locations for installation are shown in the standard plans. Guardrail is shown by proper legend on the plan sheets and the station location and quantities are tabulated on the 2B sheets. Quantities are tabulated in 12 ft. 6 in. increments. Curved sections of guardrail are to be installed on curves with a radius of 150 ft. or less. The plans specify the lengths of curved guardrail and the radius of curvature. Curved guardrail is not tabulated separately on the plans. Examples of guardrail delineation and tabulation are shown in Sample Plans.

Fill Slopes

Fill slopes can present a risk to an errant vehicle with the degree of severity dependent upon the slope and height of the fill. Providing fill slopes that are 1V:4H (4:1) or flatter can mitigate this condition. If flattening the slope is not feasible or cost-effective, the installation of a barrier might be appropriate. Figs. 5.1 through 5.3 in the AASHTO Roadside Design Guide provide guidelines to determine whether a fill slope constitutes a condition for which a barrier is a cost-effective mitigation. The curves are based on the severity indexes and represent the points where total costs associated with a traffic barrier are equal to the predicted cost of crashes over the service life for selected slope heights without traffic barrier. If the ADT and height of fill intersect on the “Barrier Considered” side of the embankment slope curve, then provide a barrier if flattening the slope is not feasible or cost-effective.

If the figure indicates that barrier is not recommended at an existing slope, that result is not justification for a deviation. For example, if the AADT is 4,000 and the embankment is 10 ft. tall, barrier might be cost-effective for a 1V:2H (2:1) slope, but not for a 1V:2.5H (2.5:1) slope. This process only addresses the potential risk of exposure to the slope. Obstacles on the slope can compound the condition. Where barrier is not cost-effective, use the recovery area formula to evaluate fixed objects on critical fill slopes shorter than 10 feet.

Guardrail is usually not used to protect traffic from headwalls located outside of the shoulder line of roadways without clear zones unless warranted by high fills. Exceptions include interstate safety modification projects where clear zones are not added and where it may not be economically feasible to extend a large box culvert to locate the headwall outside the clear zone point.

For routes under 400 AADT, guardrail for fill slopes is optional, however, good design judgment may require guardrail when conditions warrant.

Cut Slopes

A cut slope is usually less of a risk than a traffic barrier. The exception is a rock cut with a rough face that might cause vehicle snagging rather than providing relatively smooth redirection.

Analyze the potential motorist risk and the benefits of treatment of rough rock cuts located within the Design Clear Zone. Conduct an individual investigation for each rock cut or group of rock cuts. A cost-effectiveness analysis that considers the consequences of doing nothing, removal, smoothing of the cut slope, and other viable options to reduce the severity of the condition can be used to determine the appropriate treatment. Some potential options are:

W-beam guardrail barrier
Concrete barrier.

Length of Need

The length of guardrail needed to shield a fixed feature (length of need) is dependent on the location and geometrics of the object, direction(s) of traffic, posted speed, traffic volume, and type and location of traffic barrier. The length of need and the flare rate of the guardrail shall be determined in accordance with the procedures contained in Sections 5.6.3 and 5.6.4 of the AASHTO Roadside Design Guide. The general geometric data covering the length of need are illustrated on Figure 5.39 of the Roadside Design Guide.

Guardrail protection for fixed objects such as trees or utility poles may be necessary. If this protection is required, the protection is determined from the near lane on one-direction roadways and from both lanes on a two-direction roadway. Guardrail is warranted in advance of any fixed object located within the clear zone provided the object is potentially more damaging than the guardrail if struck by a vehicle and the object cannot be economically removed, relocated, or made crashworthy by means of breakaway type construction. When designing a barrier for a fill slope, the length of need begins at the point where the need for barrier is recommended.

When barrier is to be installed on the outside of a horizontal curve, the length of need can be determined graphically. For installations on the inside of a curve, determine the length of need as though it were straight. Also, consider the flare rate, barrier deflection, and barrier end treatment to be used.

When guardrail is placed in a median, consider the potential for impact from opposing traffic when conducting a length of need analysis. When guardrail is placed on either side of objects in the median, consider whether the trailing end of each run of guardrail will shield the leading end of the opposing guardrail. Shield the leading end when it is within the clear zone of opposing traffic. This is also a consideration for outer roads.

Before the actual length of need is determined, establish the lateral distance between the proposed barrier installation and the object shielded. Provide a distance that is greater than or equal to the anticipated deflection of the longitudinal barrier (See standard plans for barrier deflections). Place the barrier as far from the edge of the traveled way as possible while maintaining the deflection distance.

If the end of the length of need is near an adequate cut slope, extend the guardrail and embed it in the slope or attach it to a rock cut. Avoid gaps of 300 feet or less. Short gaps are acceptable when the guardrail is terminated in a cut slope. If the end of the length of need is near the end of an existing barrier, it is recommended that the barriers be connected to form a continuous barrier. Consider maintenance access issues when determining whether or not to connect barriers.

Barrier Deflections

Expect all barriers except rigid barriers (such as concrete bridge rails) to deflect when hit by an errant vehicle. The amount of deflection is primarily dependent on the stiffness of the system. However, vehicle speed, angle of impact, and weight also affect the amount of barrier deflection. For flexible and semirigid roadside barriers, the deflection distance is designed to help prevent the impacting vehicle from striking the object being shielded. For unrestrained rigid systems (unanchored precast concrete barrier), the deflection distance is designed to help prevent the barrier from being knocked over the side of a drop-off or steep fill slope (1V:2H [2:1] or steeper).

In median installations, design systems such that the anticipated deflection will not enter the lane of opposing traffic using deflection values that were determined from crash tests. When evaluating new barrier installations, consider the impacts where significant traffic closures are necessary to accomplish maintenance. Use a rigid system where deflection cannot be tolerated, such as in narrow medians or at the edge of bridge decks or other vertical drop-off areas. Runs of rigid concrete barrier can be cast in place or extruded with appropriate footings.

In some locations where deflection distance is limited, anchor precast concrete barrier. Unless the anchoring system has been designed to function as a rigid barrier, some movement can be expected and repairs may be more expensive. Use of an anchored or other deflecting barrier on top of a retaining wall without deflection distance provided requires approval from the Design Division.

Refer to Table 606.1.3.1 for barrier deflection design values when selecting a longitudinal barrier. The deflection distances for cable and guardrail are the minimum measurements from the face of the barrier to the fixed feature. The deflection distance for unanchored concrete barrier is the minimum measurement from the back edge of the barrier to the drop-off or slope break. The minimum offset to the obstacle can be eliminated completely by attaching the rail to the obstacle by use of a bridge anchor section.

Table 606.1.3.1 Barrier Type System Type Deflection Cable barrier Flexible Min. 8 ft.
(face of barrier to object) Type A guardrail Semirigid 4 ft.
(back of post to object) Type E guardrail Semirigid 2 ft.
(back of post to object) MGS guardrail Semirigid 2 ft. 6 in.
(back of post to object) MGS, 3’ 1 ½” post spacing Semirigid 2 ft.
(back of post to object) MGS, 1’ 6 ¾” post spacing Semirigid 1 ft. 6 in.
(back of post to object) MGS guardrail, double faced Semirigid 2 ft.
(back of post to object) Permanent concrete barrier, unanchored Rigid Unrestrained 3 ft.1
(back of barrier to object) Temporary concrete barrier, unanchored Rigid Unrestrained 2 ft.2
(back of barrier to object) Precast concrete barrier, anchored Rigid Anchored 6 in.
(back of barrier to object) Rigid concrete barrier Rigid No deflection 1 When placed in front of 2:1 or flatter fill slope, the deflection distance can be reduced to 2 feet. 2 When used as temporary bridge rail, anchor all barrier within 3 feet of drop-off.

606.1.3.2 End Terminals, Crash Cushions and Anchors

A guardrail anchor is needed at the end of a run of guardrail to develop tensile strength throughout its length. In addition, when the end of the barrier is subject to head-on impacts, an end treatment is needed. End treatments generally fall into two categories: end terminals and crash cushions.

Guardrail should be extended outside of the clear zone, or the guardrail end is to be embedded into an adjacent embankment or attached to a solid rock face to eliminate the need for a crashworthy end treatment. If these options are not practical, all approach ends of guardrail are provided with a crashworthy end treatment. All downstream ends on two-way roadways are provided with a crashworthy end treatment. Downstream ends on dual lane highways that are not within the clear zone of the opposing lanes need only be treated with end anchors. The plans are to indicate where a crashworthy end treatment is to be installed and a separate payment is made for each crashworthy end treatment.

During the project development process, use the following guidance to determine the guardrail improvements for your project.

Use MASH crashworthy end terminals for exposed ends of all new runs of guardrail on all routes.

On dual lane facilities, guardrail end terminals are to be upgraded with MASH crashworthy end terminals in both directions even if the project covers only rehabilitation of the roadway in one direction.

On major routes, replace all existing Pre-350 and 350 end terminals with MASH crashworthy end terminals.

Downstream Pre-350 and 350 end terminals outside of the major route clear zone may remain in place as long as the terminal provides sufficient anchorage to the guardrail system.
End terminals within the limits of ramps will be upgraded to MASH crashworthy end terminals. Improvements to existing guardrail that extends beyond the limits of the ramp onto the crossing route will be up to the judgment of the engineer of record.

On major routes, guardrail or concrete barrier blunt ends located on either side of a two-way roadway or on the guardrail approach end of dual lane facilities must be replaced with a MASH crashworthy end terminal even if the project covers only rehabilitation of the roadway in one direction.
Median Pier Protection: All undamaged bullnose systems may remain in place. Any Pre-350 and 350 end terminals (not protected by guard cable) and Non-350 Guardrail on median pier protection systems shall be replaced with MASH approved end terminals and MGS guardrail.
On minor routes, damaged end terminals shall be replaced with MASH crashworthy end terminals.
On minor routes, existing end terminals (in serviceable condition) may be left in place. Engineering judgment in accordance with AASHTO’s Roadside Design Guide and crash history should be used to determine guardrail improvements for each project.

Grading for New Roadway Construction. When an end terminal falls within the limits of an area that includes construction of a new roadbed, provide the needed embankment (cut/fill) quantities to construct the Standard Grading Limits shown in Standard Plan 606.81 and include that volume in the model. Indicate in the Summary of Quantities for Crashworthy End Terminals that “Standard Grading Limits” are required and that payment is included in the embankment quantities.

See Roadside Design Guide 4th Edition , Chap. 8.3.3 (pages 8-4, 5, 6 and 7), for further information on grading. On projects without earthwork pay items, Class III shaping slopes shall be used to provide the flat recovery area.

Grading for Existing Roadbeds. When end terminals are to be installed on an existing roadway, an evaluation of each location should be made to determine if an existing platform is already in place that meets the Standard Grading Limits shown in Std. Plan 606.81. If a sufficient platform does exist, indicate in the Summary of Quantities for Crashworthy End Terminals that no grading is necessary.

If an existing platform does not exist, or is insufficient, evaluate the existing terrain and determine whether the Standard Grading Limits can reasonably be constructed with Shaping Slopes Class III without creating an excessively steep in-slope or blocking the ditch with fill (that is, project scope generally does not include purchasing new right of way and/or making significant alterations to the existing in-slopes/back-slopes/ditches). For most existing locations, retrofitting the terrain to meet the Standard Grading Limits is not feasible, but if it is, indicate in the Summary of Quantities for Crashworthy End Terminals that Standard Grading Limits are required and include the necessary quantities for Shaping Slopes Class III.

If it is not practical to construct the Standard Grading Limits but Alternate Grading Limits can reasonably be constructed, indicate in the Summary of Quantities for Crashworthy End Terminals that “Alternate Grading Limits” are required and include the necessary quantities for Shaping Slopes Class III. This is the most common option for existing roadways.

Shaping Slopes Class III should not be used if the existing terrain requires significant quantities of fill. When significant grading is required, other grading pay items should be used with specific volumetric quantities to provide the flat recovery area.

If the existing terrain is such that Alternate Grading Limits cannot be reasonably constructed within the project scope, a design exception may be necessary.

See Roadside Design Guide 4th Edition , Chap. 8.3.3 (pages 8-4, 5, 6 and 7), for further information on grading.

Bridge End Treatment

Guardrail is placed at bridge ends in accordance with typical locations shown in the standard plans on most routes. When the bridge end is shielded with guardrail, crashworthy end terminals are provided.

On certain low-volume highways throughout the state, bridge ends may be delineated in lieu of shielding. This option is viable where the operating speed is less than 60 mph and the design AADT is 400 or fewer vehicles per day. The delineation-only option is primarily governed by the parameters of speed and volume. Irrespective of any values for these parameters, however, the use of delineation-only is prohibited on Major Routes as well as the National Highway System (NHS).

Use of the delineation-only option is not recommended on bridge ends in areas of poor geometry (horizontal alignment, vertical alignment, sight distance, etc.). Nor is it recommended in areas with a crash history (as calculated between two points at least 0.25 miles from either approach) in excess of the statewide average for similar road. If further analysis of either of these situations proves the delineation option to be viable, then a design exception should be obtained for its use.

Additionally, the delineation-only option should be limited to those bridge replacements or rehabilitations where the existing structure was unshielded or the existing roadway template cannot reasonably accommodate the installation of guardrail.

If you are looking for more details, kindly visit guardrail spacer.

Guardrail is not generally used to protect traffic from the ends of bridges carrying a crossroad or street over the through lanes in developed areas where speed controls exist or sidewalks are provided. If however, at ends of such bridges the roadway is in a high fill or has sharp curvature, guardrail may be considered.

Embedded and Rock Face Terminals

An embedded terminal is designed to terminate the guardrail by burying the end in a backslope. The embedded terminal is the preferred terminal because it eliminates the exposed end of the guardrail. The embedded terminal uses a concrete block anchor or embedded steel post to develop the tensile strength in the guardrail. The backslope needed to install an embedded terminal is to be 1V:3H (3:1) or steeper and at least 4 ft. above the roadway. The entire embedded terminal can be used within the length of need for backslopes of 1V:1H (1:1) or steeper if the barrier remains at full height in relation to the roadway shoulder to the point where the barrier enters the backslope. For backslopes between 1V:1H (1:1) and 1V:3H (3:1), design the length of need beginning at the point where the W-beam remains at full height in relation to the roadway shoulder usually beginning at the point where the barrier crosses the ditch line. If the backslope is flatter than 1:1, provide a minimum 20-ft. wide by 75 ft. long distance behind the barrier and between the beginning length of need point at the terminal end to the mitigated object to be protected.

For new installations, flare the guardrail to the foreslope/backslope intersection using a flare rate that meets the criteria in Standard Plan 606.30 and or Standard Plan 606.80. Provide a 1V:4H (4:1) or flatter foreslope into the face of the guardrail and maintain the full guardrail height to the foreslope/backslope intersection in relation to a 1V:10H (10:1) line extending from edge of shoulder breakpoint.

For rock cuts with a smooth face, a rock face guardrail anchor is the preferred terminal. This option should not be used on rock cuts with a rough face that might cause vehicle snagging rather than providing relatively smooth redirection.

Crashworthy End Terminals and Crash Cushions

If an embedded terminal or rock face anchor cannot be installed, consider installing a crashworthy end terminal and/or crash cushion. Crashworthy end terminals and crash cushions are devices used to provide an acceptable level of safety to the end of a roadside barrier or fixed object. Such treatment is required because of the serious consequences that may result from a vehicle impacting an unprotected barrier or object. An unprotected barrier or object can cause an impacting vehicle to abruptly stop, become unstable or roll; it can even penetrate the passenger compartment, all of which increase the risk of injury to the vehicle’s occupants.

End terminals or crash cushions that have met the safety requirements contained in MASH are deemed crashworthy and must be listed as eligible for use on the NHS by FHWA. MoDOT then reviews these items and makes a determination of their use on Missouri’s state-owned roadways. Refer to MoDOT’s End Terminals, Crash Cushions and Barrier Systems website for more information on approved crashworthy end terminals.

While crashworthy end terminals do not require an offset at the end, a flare is recommended so the end piece does not protrude into the shoulder. These terminals may have a 2 ft. offset to the first post. Four feet of widening is needed at the end posts to properly anchor the system. When widening includes an embankment, fill material will be necessary for optimum terminal performance. (See Standard Plan 606.30 for widening details.) When the entire barrier run is located farther than 12 ft. beyond the shoulder break point and the slopes are greater than 1V:10H (10:1) and 1V:6H (6:1) or flatter, additional embankment at the terminal is not needed. Crashworthy end terminals located within 10 ft. of the edgeline will be delineated with a Type 3 Modified Object Marker.

Currently, there is not a MASH approved flared-end terminal system. However, if a flared-end terminal is needed, there are NCRHP 350 systems available. These designs include an anchor for developing the tensile strength of the guardrail. The length of need begins at the third post for two approved flared terminals. When a flared terminal is specified, it is critical the embankment quantity also be specified so the area around the terminal can be constructed as shown in the standard plans.

Additional information on crashworthy end terminals and internet links to approved terminals MoDOT's end terminal website EPG .4 Crashworthy End Terminal and Qualified Plastic Guardrail Block

There are five distinct types of end terminals and crash cushions; Type A, B, C, D and E. This classification aids in the designers’ selection of the appropriate treatment for a given context. It is important to note each of these treatments reduces driver risk to equally acceptable levels and the classifications are based merely on the benefit/cost associated with replacement or repair.

Each type is classified as follows:

End Terminals

Type A. Type A end terminals are treatments used for one-sided barriers such as roadside guardrail or roadside concrete barrier. These devices can also be used on one-sided barriers in the median, provided sufficient clear space is available behind the system to allow opposite direction traffic to recover from an errant path.

Crash Cushions

Type B. Type B crash cushions are end treatments used for double-sided barriers, most often in the median. These devices can safely be impacted from several angles including the opposite direction. Type B crash cushions cannot be installed in paved surface locations unless the installation is temporary and the paved area will be resurfaced after the system’s removal.

Type C. Type C crash cushions are an end treatment used for double-sided barriers, in gore areas and in the median. Like the Type B, this device can safely be impacted from several angles usually ranging from head-on to the opposite direction. Type C crash cushions, however, may be installed in both paved and unpaved surface locations, but must be installed on an asphalt or concrete pad in non-paved areas. After impact, these crash cushions are usually damaged beyond repair and as such, should be used only in areas where low, annual-impact frequencies are expected.

Type D. Type D crash cushions have all of the installation and performance parameters of the Type C, but must be at least 80% reusable and have the ability to be reset manually with a moderate amount of repair. Type D crash cushions should be used in gore areas or medians with moderate traffic volumes and where high-impact frequencies are expected.

Type E. Type E crash cushions have all of the installation and performance parameters of the Type C but must have the ability to reset with little or no manual intervention and have an average cost of repair under $250 per event. Type E crash cushions should be used in gore areas or medians with high traffic volumes and where high-impact frequencies are expected.

Use the following decision matrix to help determine the appropriate end treatment for a given context, not to determine whether or not a barrier or object should be protected. The expected crashes per year are on an average basis:

End Treatment Decision Matrix One-Sided Protection Required Two-Sided Protection Required Non-traversable Terrain Beyond the Terminal Traversable Terrain Beyond the Terminal Fewer than 0.5 Crashes Per Year Expected 0.5 or More Crashes Per Year Expected Unpaved Paved or Unpaved Major ADT <75,000 Minor ADT <30,000 Major ADT ≥75,000 Minor ADT ≥30,000 Type A (energy absorbing) Type A (non-energy absorbing) Type B Type C Type D Type E

Sand barrels are a crash cushioning system most often used to shield fixed objects that cannot be removed or relocated. Sand barrels are recommended for temporary usage such as in work zones. Conduct a benefit/cost analysis before sand barrels are installed in a permanent application and consult with Maintenance staff. For more information, refer to EPG 612.2 Sand-Filled Impact Attenuators (Sand Barrels).

Other Anchor Applications

End anchors are used to develop the tensile strength of the guardrail at the end of guardrail runs where a crashworthy end terminal is not needed.

606.1.3.2.1 Crashworthy End Terminals with Curb

When curb is present in front of and parallel to a crashworthy end terminal (CET), the potential exists the CET will not perform as designed (i.e. will not redirect the vehicle). When installing CETs, for new construction and roadway upgrades, the need for the curb and the curb height at the location of the CET shall be considered. See EPG 749 Hydrologic Analysis and EPG 640.1 Pavement Drainage to calculate the drainage needs in and around CETs. Gutters might be able to be spread out or curb heights reduced in the vicinity of the CET while still accommodating drainage needs and the installation of the CET. Drainage calculations shall be documented in eProjects.

When curb is present in front of and parallel to the CET, the project file should have documentation regarding the design selected and considered in the following priority order:

1. Eliminate the curb or do not install new curb for the entire length of the CET with an additional 30’-50’ of curb removed upstream of the CET.

2. Reduce the curb or install new curb to a height of two (2) inches for the entire length of the CET with an additional 30’-50’ upstream of the CET.

3. Reduce the curb or install new curb to a height of four (4) inches for the entire length of the CET with an additional 30’-50’ upstream of the CET.

If a two-inch curb is not adequate for the drainage needs, a four-inch curb may be installed but is the maximum curb height allowed when installing a CET.

606.1.3.3 Transitions and Connections

When there is an abrupt change from one barrier type to a more rigid barrier type, a vehicle hitting the more flexible barrier is likely to be caught in the deflected barrier pocket and directed into the more rigid barrier. This is commonly referred to as “pocketing.” A transition stiffens the more flexible barrier by decreasing the post spacing, increasing the post size, and using stiffer beam elements to eliminate the possibility of pocketing. A transition is needed when connecting guardrail to a more rigid barrier or a structure, or when a rigid object is within the deflection distance of the barrier.

Bridge Connections

Guardrail is placed at bridge ends in accordance with typical locations shown in the standard plans. Guardrail placed for bridge end protection is anchored to the bridge end by a vertical barrier transition section. Existing bridge end connections that do not conform to current standards are to be considered for replacement or modification. In order to determine the appropriate solution for the specific non-standard bridge end connection, the Bridge Division Liaison Engineer is to be consulted. Where guardrail at the downstream end of a one-way bridge is necessary because of a high fill or other condition, the guardrail is connected to the vertical transition section.

The post spacing for MGS vertical bridge transitions varies from the previous bridge transition sections for Type A guardrail. If an existing bridge anchor section is replaced, an evaluation of the impact to drain basins should be conducted.

Additional Information Common Bridge Barrier and Railing (for Rehabilitations) Table

606.1.3.4 Median Barrier Selection and Placement

The most desirable barrier installation uses the most flexible system appropriate for the location and one that is placed as far from the traveled way as practicable. Good engineering judgment is called for in determining the appropriate placement of barrier systems. Solutions may need to be arrived at while considering competing factors such as crash frequency and severity. As discussed previously, performance of the system relies on the interaction of the vehicle, driver and system design at any given location. Additionally, the ability to access the system for maintenance and the need for access across the barrier play into the final decision.

With median barriers, the deflection characteristics and placement of the barrier for a traveled way in one direction can have an impact on the traveled way in the opposing direction. In addition, the median slopes and environmental issues often influence the type of barrier that is appropriate.

In narrow medians, avoid placement of barrier where the design deflection extends into oncoming traffic. Narrow medians provide little space for maintenance crews to repair or reposition the barrier. Therefore, avoid installing deflecting barriers in medians that provide less than 8 ft. from the edge of the traveled way to the face of the barrier.

In wider medians, the selection of barrier might depend on the slopes in the median. At locations where the median slopes are relatively flat (1V:10H [10:1] or flatter), unrestrained precast concrete barrier, beam guardrail and cable barrier can be used depending on the available deflection distance. At these locations, position the barrier as close to the center as possible so that the recovery distance can be maximized for both directions. There may be a need to offset the barrier from the flow line to avoid impacts to the drainage flow.

In general, cable barrier is recommended with medians that are 30 ft. wide or wider. However, cable barrier may be appropriate for narrower medians if adequate deflection distance exists. Refer to EPG 606.2.3 Design and Installation Guidelines for design and installation guidelines for cable barriers. Do not use concrete barrier at locations where the foreslope into the face of the barrier is steeper than 1V:10H (10:1).

At locations where the roadways are on independent alignments and there is a difference in elevation between the roadways, the slope from the upper roadway might be steeper than 1V:6H (6:1). In these locations, position the median barrier along the upper roadway and provide deflection and offset distance as discussed previously. Barrier is generally not needed along the lower roadway except where there are fixed features in the median. When W-beam barrier is placed in a median as a countermeasure for cross-median crashes, design the barrier to be struck from either direction of travel. For example, the installation of beam guardrail might be double-sided.

Guardrail may be specified in medians to provide a positive barrier. Guardrail may also be specified to convert an existing raised curb median to a barrier median provided the top of the MGS guardrail is placed 31 in. above the pavement elevation at the curb face. Double faced MGS guardrail may be used on a raised median width of 2 ft. back-to-back. For greater widths, two single lines of MGS guardrail will be required.

For medians of variable widths, a detail in the standard plans provides for transition from single faced to double faced guardrail. Crashworthy end terminals are added only at the beginning and ending of a total run of guardrail and not at each break caused by intersections and median openings. Breaks caused by intersections and median openings will be closed by means of a crashworthy special end treatment.

Double faced MGS guardrail can be used on a flush median, as shown in the figure below. Double faced MGS guardrail is to be used where a median barrier is to be provided but site conditions will not permit the use of a concrete barrier (drainage, visibility requirements, aesthetics, etc.). The concrete barrier is generally limited to the high volume roadways with narrow width medians.

Bullnose Guardrail System

The bullnose guardrail system may be used in the medians of expressways or freeways to shield drivers from hazards, such as bridge piers and other obstacles. It is not a crashworthy end terminal, but is rather a non-gating barrier principally constructed of Type E guardrail. As long as the median’s vertical differences are minimal or can be minimized through grading, the bullnose guardrail system is an appropriate treatment for new construction. This system requires at least 15 ft. of median width for its construction. The bullnose guardrail system is not to be erected between twin bridges. Alternatives are available for twin bridge protection in Standard Plan 606.01. Consult Standard Plan 606.30 for grading requirements and other important details.

606.1.3.5 Closures of Existing Streets, Roads, Bridges or Non-Traversable Roads

606.1.3.5.1 Closures of Existing Streets and Roads

When closing a street or road, use either Type 4 Object Markers only or a combination of Type 4 Object Markers and Type D guardrail as shown in Figs. 606.1.3.5.1.1 and 606.1.3.5.1.2. Where no hazard exists beyond the end of the closed street or road for a reasonable distance, Type 4 Object Markers are sufficient for delineation. Where a hazard exists beyond the end of the closed street or road that is considered equal to or greater than that created by the use of guardrail (for example a removed bridge or culvert, or a structurally deficient bridge), a combination of both Type 4 Object Markers and Type D guardrail is specified. Refer to EPG 903.17.5 Object Markers for Ends of Roadways and Standard Plan 903.00.

Fig. 606.1.3.5.1.1, Type 4 Object Markers Fig. 606.1.3.5.1.2, Type 4 Object Markers
with Type D Guardrail

Additional emphasis of a sign barricade may be required for horizontal and vertical alignment of the roadway and at tee intersections as shown in Fig. 606.1.3.5.1.3. Location and installation guidelines for sign barricades are located in EPG 903.6.53 Sign Barricades, and Standard Plan 903.02 Highway Signing.

Fig. 606.1.3.5.1.3, Sign Barricade with Type 4 Object Markers

606.1.3.5.2 Closure of Existing Bridges or Non-Traversable Roads

Bridges and roadways may be closed to the traveling public due to natural aging process of the structure, weather damage (ex. flooding), bridge/roadway slides, etc.

Restoration of the bridges and roadways may be delayed due to scheduling constraints or budget costs of projects. District personnel and Central Office Bridge Division personnel should discuss the schedule to repair the bridge. District personnel and Central Office Construction/Material Geotechnical personnel should discuss the schedule to repair the roadway. Based on the repair schedule, the district will determine the type of closure needed for the bridge or roadway.

For bridge and/or roadway closures, bridge/roadways shall be closed according to typical application EPG 616.8.8A (TA-8A) Road Closure or EPG 616.8.8B (TA-8B) Road Closure with Barrier.

For less than one month closure duration, the district may use Type 3 barricades as shown in Fig. 606.1.3.5.2.1.

For six-month closure durations, the district may use Type 3 barricades and temporary concrete traffic barriers as shown in Fig. 606.1.3.5.2.2. As shown in the typical application, the temporary concrete traffic barriers should have red reflective sheeting across the face of the barrier.

Fig. 606.1.3.5.2.1, Bridge Closure with Type 3 Barricades Fig. 606.1.3.5.2.2, Bridge Closure with
Type 3 Barricades and Temporary Barriers

For longer closure durations, the district may use Type D guardrail and Type 4 object markers as shown in Fig. 606.1.3.5.2.3.

Fig. 606.1.3.5.2.3, Bridge Closure with Type
D Guardrail and Type 4 Object Markers

When closing bridges and/or roadway, the more temporary devices used will require additional attention compared to permanent devices.

606.1.4 Maintenance Planning Guidelines for Guardrail

Printable Maintenance Planning Guideline for Guardrail.

For more information, please visit Custom Hot Dip Galvanized Guardrail.

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