AASHTO Specs for Safety Barriers

This article relates to specifications for construction of crashworthy metal beam and rope cable guardrail, New Jersey concrete and other similarly shaped safety barriers, barrier terminals, portable and permanent impact attenuators, glare screens, and steel safety railing. It also include specifications for the reinstallation/retrofitting of metal beam and rope cable guardrail, New Jersey Concrete Barriers and guardrail terminals, impact attenuators and steel safety railings which will need to be in conformity with the lines and grades shown on the plans or established by the Engineer.

Materials

Metal Beam Guardrail.

Rail elements and backup plates for W-Beam or Thrie-Beam rail shall conform to the requirements of AASHTO M 180, Class A, Type 2 galvanized. Rail elements to be erected on a radius of forty-five (45) meters or less shall be shaped in the shop. The radius of curvature shall be stencilled on the back of each section of rail. Rail elements shall be designed to be spliced at intervals not to exceed either four (4) or eight (8) meters and such splices shall be made at posts, unless otherwise shown on the plans.

Tensioned Four Rope Wire Rope Guardrail. The ropes shall be of nineteen (19) millimeter diameter 3x7 (6/1) coreless construction having a minimum breaking load of seventeen and seven-tenths (17.7) tons. The rope shall exhibit a minimum modulus of elasticity of eight thousand three hundred (8300) kilograms per square millimeter based on an area of two hundred eighty-three (283) square millimeters, after pre-stressing by an approved method to ensure the ropes behave elastically and retain their tension in service.

All wire used for the manufacture of the ropes shall be general purpose wire to BS 2763 grade 1370, A, or to AASHTO M30, Type II, finally zinc coated by the hot dip method.

All threaded terminals and rigging screws shall be hot dip galvanized to BS 729 or AASHTO M232.

The posts, which are designed to collapse on impact, shall be one thousand and eighty (1080) millimeters long, six (6) millimeters thick steel to BS 4360 grade 50A, one hundred (100) millimeters by thirty-two (32) millimeters "Z" (median applications) or "S" section (shoulder applications) as determined by the contract but always with the rounded edge of the post facing the traffic, and shall be slotted at one end through the center of the web one hundred thirteen (113) millimeters deep by twenty-two (22) millimeters wide prior to galvanizing, in which the ropes are located. A black polyethylene cap to which is affixed a retroreflective Class 1 prismatic reflector (color to be specified in the contract) complying with Table 1 of BS 873: Part 6, shall be placed on the top of the post. A polyethylene excluder shall be placed at the bottom of the post to prevent the ingress of sand, etc., into the foundation.

The anchor frames shall be fabricated from mild steel and galvanized to BS 729 before being embedded in a block of concrete one and twenty-two hundredths (1.22) meters long by one (1) meter wide by one (1) meter deep.

A check rope, one and eight-tenths (1.8) meters in length, eight (8) millimeters diameter, with a minimum breaking load of three and nine-tenths (3.9) tons when tested as an assembly, fitted with a galvanized thimble at one end and a fork terminal at the other, shall be provided at each anchor. The thimble shall be passed over the end of the tail rope and the fork terminal connected to the anchor.

?Other Wire Rope. Wire rope for metal beam guardrail anchor terminals shall conform to AASHTO M 30, Type II, Class A. Equivalent galvanized wire rope with a minimum breaking strength of nineteen thousand four hundred (19,400) kilograms will be acceptable.

Posts and Miscellaneous Barrier Rail Hardware

Unless otherwise indicated on the plans, all steel posts, plates, angles, channels, brackets, and anchor assembly units shall conform to the requirements of ASTM A 36. Cold rolled post sections shall conform to the requirements of ASTM A 446, Grade B.

The swage fittings for anchor terminals shall be machined from hot-rolled carbon steel conforming to the requirements of ASTM A 576, Grade 1035, and shall be annealed suitable for cold swaging. A lock pin hole shall be drilled through the swage fitting head to accommodate a seven (7) millimeter, plated, spring steel pin to retain the stud in the proper position. The stud shall be steel conforming to the requirements of ASTM A 449. Prior to galvanizing, a ten (10) millimeter slot for the locking pin shall be milled into the stud end. The swage fitting, stud, and nut shall develop the full breaking strength of the wire cable.

Anchor rod eyes shall be hot forged or formed with full penetration welds. After fabrication, anchor rods with eyes that have been formed with any part of the eye below eight hundred seventy degrees Celsius (870_ C) during the forming operation or with eyes that have been closed by welding shall be thermally stress relieved prior to galvanizing. The completed anchor rod, after galvanizing, shall develop a strength of twenty-three thousand (23,000) kilograms.

All bolts shall conform to the requirements of ASTM A 307, except those designated on the plans as high strength shall conform to the requirements of ASTM A 325 or A 449. All nuts shall conform to the requirements of ASTM A 563, Grade A or better, except those designated on the plans as high strength shall conform to the requirements of ASTM A 563, Grade C or better.

Clevises shall be drop forged galvanized steel and shall develop the full specified breaking strength of the wire cable.

The concrete insert assembly for Type 4 anchor terminals shall be fabricated as shown on the plans. Ferrules shall be steel conforming to the requirements of ASTM A 108, Grade 12 L 14. Inserts shall be tapped to the dimensional requirements specified in ASTM A 563 for nuts receiving galvanized bolts. Insert assembly wires shall conform to the requirements of ASTM A 510, Grade 1030, and have a minimum tensile strength of seven thousand (7,000) kilograms per square centimeter. Welded attachment of wire to ferrule shall develop the full tensile strength of the wire.

Turnbuckles shall be steel of commercial quality and shall have a minimum breaking strength of one thousand five hundred (1,500) kilograms. Turnbuckles shall be galvanized in accordance with ASTM A 153. Compensating and non-compensating cable ends shall be cast steel conforming to the requirements of ASTM A 27 or malleable iron conforming to the requirements of ASTM A 47. Compensating devices shall have spring constants of eight thousand (8,000) kilograms per meter, plus or minus five hundred (500) kilograms per meter and permit a travel of one hundred fifty (150) millimeters, plus or minus twenty-five (25) millimeters. All elements shall be galvanized. The cable connecting hardware shall develop the full strength of the wire rope. At all locations where the cable is connected to a cable end with a wedge type connection, one (1) wire of the wire rope shall be crimped over the base of the wedge to hold the cable firmly in place.

Galvanizing

All of the exposed materials for guardrail, guardrail anchor terminals, impact attenuators, glare screen, and delineators, which are made of steel or iron, shall be galvanized after fabrication unless otherwise specified. Galvanization shall be in accordance with the specific referenced specification. When no galvanization requirements is included in the specification, galvanization shall be in accordance with ASTM A 123 or ASTM A 153 as appropriate.

All components shall be fabricated and galvanized for installation without further drilling, bending, cutting or welding. When field modifications are approved by the Engineer, or when minor damage to the galvanized coating occurs, the exposed surface shall be repaired by thoroughly cleaning and applying two (2) applications of Paint No. 3 as specified in Paragraph 5.13.2.6, "Zinc Dust-Zinc Oxide Primer" in these General Specifications.

Glare Screens

Glare screens shall be chain-link mesh conforming to ASTM A 491 or ASTM A 392 or plastic slats as detailed on the plans and in the Bill of Quantities. Chain-link mesh size and wire diameter shall be as specified in the plans.

Posts shall be galvanized steel pipe conforming to ASTM A 53 of the diameter shown on the plans. Posts shall be furnished with galvanized watertight caps.

Tension wire shall conform to ASTM A 641, Class 1, Hard Temper, with a minimum diameter of four and five tenths (4.5) millimeter.

Tension cable shall conform to ASTM A 474 or A 475, six (6) millimeter minimum diameter, high strength grade. All hardware shall be typical of that shown on the plans and shall be galvanized in accordance with ASTM A 153.

When required by the plans or Special Specifications, the fence fabric, posts, and all exposed galvanized hardware shall be coated with a minimum twenty-five hundredths (0.25) millimeter coating of bonded polyvinyl chloride (PVC). The polyvinyl chloride shall be applied by the thermal extrusion process and shall withstand a minimum exposure of one thousand five hundred (1,500) hours at sixty-two degrees Celsius (62 _ C) without any deterioration when tested in accordance with ASTM D 1499.

Slats, when required, shall be either wood or plastic and of the dimensions shown on the plans. Wood slats shall be treated with a preservative.

Plastic slats shall be made of polyethylene or polymeric materials. They shall be color pigmented and designed to retard ultraviolet penetration. The material shall remain flexible without distortion and without becoming brittle through a temperature range of zero degrees Celsius (0 _ C) to sixty degrees Celsius (60_ C). The system will use a nonmetallic base designed so the flexible slat can be retained in place by two (2) friction locking pins or a U-shaped retainer at the bottom and top of the glare screen.

Samples for the color for plastic slats shall be submitted to the Engineer for approval.

Guardrail Delineators

Hardware shall conform to the requirements shown on the plans. An acceptable alternative delineator will be a replaceable barrier marker post with a locking mechanism compatible with the base. The replaceable barrier marker post will be a minimum of three hundred fifty (350) millimeters long and seventy (70) millimeters wide. The replaceable barrier marker post should be available in a variety of colors and compatible with reflective sheeting. When shown on the Plans or stated in the Special Specifications reflective sheeting shall be placed on the approach ends of metal beam guardrail terminals and be Type IV high intensity retroreflective sheeting with Class III backing meeting the requirements of Paragraph 9.05.2.9 "Retroreflective Sheeting" in these General Specifications.

New Jersey concrete barrier delineators shall conform to the requirements of the plans, Special Specifications and M.U.T.C.D. Subsection 5.03 F. Epoxy Resin Adhesives for bonding delineators to hardened Portland cement concrete shall conform to AASHTO M 237.

Other Materials

Other materials shall be as shown in the plans, stated in the Special Specifications or in the U.S. American Road Builders Transportation Association (ARBTA) Bulletin No. 268 "A Guide to Standardized Highway Barrier Rail Hardware.” Special materials for impact attenuators shall be as specified by the manufacturer.

Reinstallation of Guardrail, Guardrail Terminals, New Jersey Concrete Barrier and Steel Safety Railing.

Metal beams, cables, posts, anchor terminal sections, concrete barriers or safety railings shall be salvaged materials, as salvaged by the Contractor and approved by the Engineer.

Bolts, nuts, washers, fittings, adhesives, and accessories shall be new materials conforming to the requirements for the construction of new guardrail, concrete barrier and steel safety railing as detailed in Section 5.05 - Steel Structures and Miscellaneous Metal Work and Section 6.01 Crashworthy Safety Barriers in these General Specifications.

Impact Attenuators

Rail elements for thrie beam rail (used in G.R.E.A.T. Impact Attenuators) shall conform to AASHTO M 180, Class B, Type galvanized. Rail element joints shall be fabricated to lap not less than thirty (30) centimeters and be bolted. The rail metal, in addition to conforming to the requirements of AASHTO M 180, shall withstand a cold bend, without cracking, of two hundred (200) grads around a mandrel of a diameter equal to two and one half (2?) times the thickness of the sheet metal plate.

Wire rope restraining cable for G.R.E.A.T. impact attenuators shall be a minimum of twenty-two (22) millimeter nominal diameter galvanized wire rope conforming to ASTM A 603, Class A.

Pull out and secondary cable for G.R.E.A.T. impact attenuators shall be minimum nine and five tenths (9.5) millimeter nominal diameter galvanized wire rope conforming to ASTM A 603, Class A.

Restraining chains for G.R.E.A.T. impact attenuators shall be twelve (12) millimeter nominal size and shall conform to the requirements of ASTM A 413, Grade 28.

QuadGuard metal work shall be fabricated from either M1020 Merchant Quality or ASTM A-36 steel. After fabrication, metal work shall be galvanized in accordance with ASTM A-123. All welding shall be done by or under the direction of a certified welder.

The QuadGuard System shall be assembled with galvanized fasteners. All bolts, nuts and washers shall be Commercial Quality “American National Standard” unless otherwise specified.

The QuadGuard diaphragms shall be made from 10-gauge steel Quad-beam sections. The diaphragms shall be available in widths of 610, 760 and 910 mm [2', 2'-6" and 3']. Two support legs shall be welded to the Quad-beam. Ski-shaped plates shall be welded to the bottom of the support legs. The diaphragms shall be designed to lock onto and be guided by a ground-mounted, center monorail support structure.

The QuadGuard fender panels shall be fabricated from 10-gauge steel Quad-beam sections. Each fender panel shall be drilled and slotted in accordance with the manufacturer’s specifications so that when assembled in the field, the front end shall be bolted to a diaphragm by means of the three (3) 15.9 mm (5/8") bolts.

Impact attenuation devices with cartridges filled with liquids, such as antifreeze agents, that may become a skid hazard when impacted, shall not be used; replaceable cartridges with foam-filled cardboard, lightweight concrete and similar materials will be acceptable. All units shall be identified by identification labels fastened at a protected but conspicuous location.

Construction and Installation Requirements

Metal W-Beam and Thrie-Beam Guardrail

Guardrail shall be installed at the locations shown on the plans or as ordered by the Engineer. Posts shall be installed by driving plumb to the required grades or set in concrete as required by the plans. When the pavement is within one (1) meter of the guardrail, the posts shall be set before placing the pavement.

If ground conditions are such that pilot holes are necessary to prevent damage to posts during driving, all space around steel posts after driving shall be filled with dry sand or fine gravel.

When posts are set in concrete, the concrete shall be placed against the excavated earth unless otherwise permitted. All curved guardrail with a radius of forty-five (45) meters or less shall be bent in the shop.

Continuous lengths of rail or cable shall be installed, and alignment checked and adjusted before final tightening of bolts, etc. Unless otherwise specified, bolted connections shall be torqued to six (6) to seven (7) kilogram-meters. Bolts that extend at least six (6) millimeters but not more than twenty-five (25) millimeters beyond the nuts shall be used.

Rail elements shall be erected in a smooth continuous line with the laps in the direction of traffic flow.

Posts may be erected by driving with approved mechanical devices. The method of driving shall not substantially alter the cross-sectional dimensions of the posts or materially damage the coating. Battered tops shall not be accepted. Posts which, in the opinion of the Engineer, are bent or otherwise damaged during or after erection, shall be removed and replaced at the Contractor’s expense.

Damaged galvanized surfaces may be repaired, only if so approved by the Engineer. Such surfaces shall be repaired by thoroughly wire brushing and then by applying two (2) coats of an approved zinc-dust zinc-oxide primer.

The guardrail ropes shall be joined together by rigging screws, which are also used for tensioning. The maximum length of anyone (1) individual rope shall be one hundred fifty-four (154) meters. Immediately prior to each anchorage there shall be a tail rope six (6) meters in length and connected to the anchorage in the ground. All ropes shall be fitted on each end with a threaded terminal of right hand or left-hand thread as appropriate to ensure a right hand and left-hand thread is in the rigging screw to effect the tension. A minimum insertion of twenty-five (25) millimeters into the rigging screw is required. The tail rope shall have a right-hand thread on the end which is connected to the anchor.

The installation of the cable guardrail shall be in accordance with the manufacturer's instructions and working drawings.

The foundation for the post shall be as detailed on the manufacturer's working drawings unless advised otherwise in the Contract due to local ground conditions. It shall be of sufficient size to ensure that it is not displaced when the post is knocked down, and withstand an overturning moment of six thousand (6000) Nm.

When all the components are in place, the ropes shall be uniformly tensioned to 25 kN by turning the rigging screws. Backfill above the tops of concrete anchor footings shall not be placed before the cables are tensioned.

Guardrail Anchor Terminals

Guardrail anchor terminals shall be installed at the locations shown on the plans or ordered by the Engineer.

Posts, anchors, and footings shall be driven or installed in concrete as required.

Concrete shall be placed against the excavated earth unless otherwise permitted.

Bolted connections shall be torqued to six (6) to seven (7) kilogram-meters unless otherwise specified.

New Jersey Concrete Barriers and Terminal Sections

Concrete barriers shall present a smooth, uniform appearance in their final position, conforming to the horizontal and vertical lines shown on the plans or ordered by the Engineer, and shall be free of lumps, sags, or other irregularities. The top and exposed faces of the barrier shall not vary more than more than six (6) millimeters between any two (2) contact points when tested with a four (4) meter straightedge laid on the surfaces. Transverse expansion joints of one (1) centimeter thick pre-moulded filler shall be provided in all New Jersey Barriers at spacings not exceeding fifteen (15) meters center to center.

Concrete barriers may be precast, cast-in-place with fixed forms, or extruded with slip forms at the Contractor's option. Concrete barriers constructed by casting-in-place with fixed forms shall conform to the provisions in Section "Concrete Structures" in the General Specifications (to be published later)

Concrete barriers constructed by means of an extrusion machine or other similar type equipment shall be of thoroughly consolidated concrete, and the exposed concrete surfaces shall conform to the requirements of Section "Concrete Structures" in the General Specification (to be published later)

Construction and Installation Requirements

The Contractor shall furnish evidence of successful operation of the extrusion machine or other equipment by constructing a trial section of barrier or by other evidence suitable to the Engineer. Concrete shall be fed to the extrusion machine at a uniform rate. The machine shall be operated under sufficient uniform restraint to forward motion to produce a thoroughly consolidated mass of concrete free from surface pits larger than two (2) centimeters in diameter and requiring no further finishing. The concrete shall be of such consistency that, after extrusion, it will maintain the shape of the barrier without support. The grade for the top of the concrete barrier shall be indicated by an offset guideline set by the Contractor and approved by the Engineer. The forming portion of the extrusion machine shall be readily adjustable vertically during the forward motion of the machine to conform to the predetermined grade line. A grade line gauge or pointer shall be attached to the machine in such a manner that a continual comparison can be made between the barrier being placed and the established grade line as indicated by the offset guideline. Other means of controlling barrier grade may be permitted by the Engineer. Expansion joints of the width shown on the plans shall be constructed by sawing through the barrier section to its full width. If sawing is performed before the concrete has hardened, the adjacent portions of the barrier shall be firmly supported with close fitting shields. When sawing is performed after the application of curing compound, the exposed faces of the barrier in the vicinity of the joint shall be treated with curing compound after sawing the joint.

If stationary forms for concrete barriers are used, they shall be removed as soon as possible after the concrete has set enough to maintain the shape of the barrier without support in order to facilitate finishing. The surface shall be free from pits larger than two (2) centimeters in diameter. The surface shall be given a final soft brush finish with strokes parallel to the line of the barriers. Finishing with a brush application of grout will not be permitted. Surfaces shall be finished as necessary to produce smooth, even surfaces of uniform texture and appearance, free from bulges, depressions, and other imperfections. The use of power sanders, carborundum stones, or disks may be required to remove bulges or other imperfections.

Exposed surfaces of concrete barriers shall be cured by the "water method". The Engineer may permit the concrete barriers to be cured by means of the "curing compound method" in accordance with the provisions of Paragraph

Impact Attenuators

G.R.E.A.T. system and other impact attenuators shall be installed in accordance with the requirements, or as modified by the Contract Drawings or Special Specifications and with the manufacturer's recommendations and instructions. A copy of these recommendations and instructions shall be furnished to the Engineer upon delivery of the materials.

The QuadGuard System shall consist of crushable cartridges surrounded by a framework of steel Quad-beam guardrail which can telescope rearward during head-on impacts. The QuadGuard System shall have a center monorail which will resist lateral movement during side angle impacts. The nose shall consist of a formed plastic nose wrap.

A bay describes a section of the QuadGuard System consisting of a cartridge, a diaphragm and two fender panels. Each bay shall be fitted with an energy absorbing cartridge. The outside of the cartridge shall be fabricated from a weather resistant plastic. The front portion of the system shall be fitted with Type I cartridges. The rear portion of the system shall be fitted with Type II cartridges. All cartridges shall include a cartridge replacement indicator.

The back end of each Quad-beam fender panel shall overlap and be connected to the diaphragm of the next bay by means of a bolt and enlarged “mushroom” washer. The bolt fits through the long horizontal slot in the forward fender panel. This permits the movement, front to back, of one set of fender panels relative to the panels in the underlying-rearward bay. The back portion of each fender panel shall be tapered to help maximize performance during wrong-way, re-directive impacts.

The monorail support structure shall be made of steel and be anchored to a specified concrete pad. The monorail shall prevent lateral movement, vertical movement and overturning movement of the diaphragms during design impacts.

The nose section shall contain a nose cover and a crushable cartridge and is not counted as a bay. The nose cover shall be made from a plastic material formulated to resist weathering. The nose shall attach to the front diaphragm. Standard colors shall be gray or yellow.

Glare Screens

Glare screen fabric shall be placed on the face of the posts designated by the Engineer. On curves, the fabric shall be placed on the face of the post which is on the outside of the curve.

The fabric shall be stretched taut and securely fastened to the posts as shown on the standard plans. The fabric shall be cut and each span attached independently at all pull and brace posts. Rolls of wire fabric shall be joined by weaving a single strand into the end of the rolls to form a continuous mesh between pull posts.

Reinstallation of Guardrail

Remove and store the existing guardrail, posts and appurtenances. Remove and dispose of posts that are set in concrete. Replace and reinstall guardrail, posts and hardware damaged during removal, storage or resetting.

Reinstallation/Retrofit of Guardrail Terminals and Impact Attenuators

Remove and store the existing attenuator guardrail, hardware posts and appurtenances. Remove and dispose of posts that are set in concrete. Replace and reinstall the attenuator and including the hardware damaged or lost during removal, storage or resetting.

Quality Assurance Procedures

The guardrails and crashworthy safety barriers will be inspected, sampled, tested and evaluated.

The manufacturer of the guardrail systems shall be approved to a Quality Assurance scheme complying with ISO 9002 (eg., EN29002, BS 5750 Part 2) as a supplier of components for use in vehicle safety barriers.

Only components complying with the manufacturer's specification may be used.

Copies of Certificates of Guarantee and test reports shall be provided for the components of each guardrail system manufactured off site.