Practices for High-Tension Cable Barriers (2016)

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18 only two pages. Its major headings were Description, Materi- als, Basis of Acceptance, Construction Methods, and Method of Measurement and Basis of Payment. The description of the work simply states that it “con- sists of furnishing and installing a complete and operational Tensioned Cable Guardrail . . . and Terminal at the locations designated on the Plans and/or as directed by the Engineer, in accordance with these Specifications.” Under the Materials heading, this specification requires only that the selected sys- tem and terminal must meet either NCHRP Report 350 (Ross et al. 1993) or MASH test and evaluation criteria at TL-3, that the cable and other steel components be galvanized or stainless, and that the appropriate class of concrete be used for anchorages and footings. Under Basis of Acceptance, the specification reiterates that the system selected must have been accepted by FHWA and that it have a maximum design deflection of 8 ft. It also requires a manufacturer’s certification confirming that all hardware furnished has the same physical properties as the tested and approved design, and that the product is suitable for the project site and will perform acceptably after installation. The specification also requires the manufacturer to calculate and submit the required embedment depth for all concrete footings and to provide installation and maintenance guide- lines to state personnel. The Construction Methods section of the specification requires the contractor to “coordinate with a designated rep- resentative of the manufacturer relative to the installation . . . specified in the Contract. The manufacturer . . . shall provide any instructions and drawings that are necessary in order to properly complete installation along each alignment shown on the Plans. The Contractor shall furnish the Engineer with (these) instructions and plans prior to installation.” The spec- ification also requires the line posts to be set in sockets with a concrete footing and allows minor adjustment of post spac- ing to span drainage features, provided the design deflection is maintained. The Method of Measurement/Basis of Payment section is virtually the same for all state specifications for HTCB. The barrier proper is measured and paid for by the linear foot, excluding the end anchors, which are paid for as a separate line item. More than half of the survey respondents provided copies or links to their existing specifications or special provisions gov- erning the selection and installation of HTCB. This chapter includes summary descriptions of the content of these docu- ments from selected states. As noted in chapter three, some states have not developed a specification, but rely solely on the manufacturers’ specifications and installation manu- als. Some states use very concise specifications, whereas a few have developed extensive documents covering design, installation, and maintenance of HTCB systems. Specifications or special provisions were selected from the following six states, both to represent a geographical distri- bution across the country and to show the diversity that cur- rently exists among state agencies: Rhode Island, West Virginia, Florida, Michigan, Colorado, and Washington. As noted previ- ously, before 2010, FHWA eligibility letters were referred to as acceptance or approval letters and are still referred to as such in some of these DOT specifications and special provisions. chapter four CASE EXAMPLES RHODE ISLAND This specification (Code 901.9901, Tensioned Cable Guard- rail, and Code 901.9902, Tensioned Cable Guardrail Termi- nal) was the most condensed version submitted, consisting of

19 WEST VIRGINIA West Virginia has added information on HTCB under its Spe- cial Provision Section 607, Guardrail. The Section headings include Description, Materials, Erecting Rail Elements, and Method of Measurement/Basis of Payment. The Description section identifies the work to be done as “. . . constructing high-tension cable guardrail by furnishing and installing posts, cables, end anchors, and any special connections and fittings which may be required in the con- tract documents.” It also requires that the selected system be one that has been accepted by the FHWA as a TL-4 barrier on slopes of 6:1 and a TL-3 barrier on slopes of 4:1. It should use four cables, have a design deflection of 8 ft or less, and a maximum post spacing of 12 ft. A 3-ft by 3-in. deep concrete mow strip is required. Under Materials, the Special Provision states that “. . . all materials used for construction of High-tension Cable Guard- rail shall meet the manufacturers’ requirements. The Contrac- tor will provide certification of training from the Manufacturer in the system they are bidding. Prior to construction, the Con- tractor shall provide the Engineer with three (3) copies of the manufacturer’s most current product manuals covering instal- lation and maintenance of the installation and signed certifi- cation statements for all materials to be incorporated into the installations.” The Special Provision requires that “. . . end terminal installations shall be to the manufacturer’s specifica- tion for site-specific soil conditions,” and requires that “the contractor will guarantee movement of less than one inch of all end anchors within the first two years of installation.” The section on Erecting Rail Elements essentially requires the barrier to be installed according to the plans or as directed by the Engineer and cautions that the proper height of each cable is critical. It further states that the “wire rope shall be placed and tensioned per manufacturer’s recommendations” and that the tensioning be rechecked and adjusted if neces- sary 2 to 3 weeks after the initial tensioning. It further requires that a manufacturer’s representative be present during the initial installation of the system components, and upon com- pletion of the installation, “a manufacturer’s representative shall inspect with the installer and certify in writing that the high-tension cable guardrail was installed in accordance with the design and the manufacturer’s recommendations.” Method of Measurement/Basis of Payment section was again per foot of installed barrier, with the end anchors a separate bid item. The West Virginia Special Provision also requires the contractor to supply the state with a tension meter, 10% of all the hardware and line posts installed, and two full anchor assemblies as incidental to the bid items. FLORIDA Florida’s specification is found in Section 540, High-tension Cable Barrier System, consisting of several categories: Descrip- tion, Materials, Shop Drawings and Design Calculations, Design Criteria, Manufacturer’s Installation Representative, Construction Requirements, and Method of Measurement/ Basis of Payment. In addition to the specification, Florida DOT has also produced a companion document identified as Design Standards Index D450, which provides detailed design guidance, including placement guidelines for high-tension cable barrier at typical locations. Under Description, the contractor must “furnish and install high-tension cable barrier (HTCB) systems in accordance

20 with the requirements of the Contract Documents, the Design Standards Index D450, and the Manufacturer’s recommenda- tions.” Furthermore, the system selected must be one included in FDOT’s Innovative Product List, meet NCHRP Report 350 (Ross et al. 1993) or MASH TL-4 test and evaluation criteria, have an FHWA eligibility letter, and use four cables, with a minimum top cable height of 33 in. and a maximum bottom cable height of 21 in. Both height measurements are to be taken at a post. Section 540-2, Materials, provides specifications for the wire rope, all required fittings, line posts and sockets, end terminals, barrier delineators, and reinforced foundations. Line posts are to be set in steel sleeves encased in reinforced concrete foundations, with a maximum post spacing of 16 ft. The posts must meet the manufacturer’s specifications and be consistent with the size and shape specified in the FHWA eligibility letter. The end terminal used must also have an FHWA eligibility letter and its concrete foundation size must be determined by the manufacturer or the specialty engineer, “. . . whichever is more stringent and sufficient to prevent movement in the soil after tensioning the cables.” Shop drawings must contain construction specifications and all design details, including post lengths and height, post spacing, cable heights, and detailed drawings and locations for all connection hardware. Of particular importance are the foundation dimensions and reinforcing steel for all concrete foundations, including end terminal anchors and transition line posts, and all line posts. The design calculations must be signed and sealed by a professional engineer licensed in the state of Florida and must include end terminal and line post foundation designs prepared by the contractor’s specialty engineer. In addition, design tables including cable tension as a function of cable temperature must be included. Florida DOT has very specific requirements for the design of end terminal foundations, summarized as follows: • Use geotechnical information provided in the plans and/or furnished by the contractor if required by the manufacturer. • Minimum design load for end anchor based on the cumu- lative tension expected at zero degrees Fahrenheit. • Analyze lateral deflection of the end anchor using the P-Y Method. • Limit lateral deflection to one inch at the ground line, using a factor of safety of 2.0. • Analyze overturning resistance using Broms’ Method with a factor of safety of 2.0. • Analyze the uplift resistance using the Alpha or Beta Methods (reference FHWA-NHI-10-016) with a factor of safety of 2.0. • Determine steel reinforcement for the terminal anchor using the AASHTO Load Resistance Factor Design (LRFD) Bridge Design Specifications. Line post foundations should be based on the soil most predominant in Florida, a cohesionless sand with a friction angle of 30 degrees and a weight of 112 pounds per cubic foot (unsaturated) or 50 pounds per cubic foot (saturated). If the geotechnical data provided in the plans do not meet these soil conditions, a line post foundation design must be submitted to the engineer. The foundation design must allow the posts to reach their plastic strength limit or fracture before the founda- tions deflect one inch. The foundations must also be designed to prevent overturning, using the Broms’ Method with a factor of safety of 1.5. Reinforcing steel must be designed using the AASHTO LRFD Specifications to resist external loads or temperature and shrinkage strains, whichever requires the most reinforcing. Section 540.4 requires a manufacturer’s representative be on the jobsite prior to and during the initial work related to layout, installation of the end anchorage, post sleeves, and post hardware, as well as cable attachment and tensioning. The rep- resentative must also provide “a written letter . . . to the Engi- neer stating that the Contractor’s installation process follows the requirements outlined in the manufacturer’s installation manual and that the construction personnel received adequate training for the installation and tensioning of the cable barrier system.” Section 540.5, Construction Requirements, provides stan- dard guidelines for basic layout, site preparation, and installa- tion, including allowable tolerances for system components. The requirements for initial and final cable tensioning, how- ever, are quite detailed and summarized here: • Use certified and calibrated tension meter specified by the manufacturer. • Provide calibration certificates to the engineer 30 days before installation. • Determine required tension based on cable temperature at time of testing. • Tension cables systematically in accordance with man- ufacturer’s specifications. • Re-test and re-tension as needed between 2 and 3 weeks after initial tensioning. • Complete a tension log detailing all pertinent information on the time, temperature, location, and results of each reading and the model and serial number of the tension meter used. • Provide the engineer with two copies of the tension logs for initial, final, and any intermediate re-tensioning. • Deliver two tension meters and any additional tools needed for system maintenance to the Department before final acceptance. Method of Measurement/Basis of Payment is based on the linear footage of installed HTCB, exclusive of the end anchors. Florida divides the end terminal payments into two categories, the first being the End Terminal Assemblies, which includes end terminal posts and hardware required by the manufacturer for a complete and functioning end terminal system meeting an FHWA eligible design. The second pay category is the End Terminal Foundation based on the cubic

21 yards of concrete used and includes reinforcing steel, labor, materials, and equipment needed to complete the drilled shaft. The quantity to be paid will be based on the foundation dimensions shown on the approved shop drawings. Under Materials, the contractor must select the HTCB sys- tem to be installed from the three proprietary systems used by Michigan DOT, and provide “written certification to the Engi- neer that all components supplied by the manufacturer meet manufacturer’s specifications and this special provision.” The system selected must meet or exceed NCHRP Report 350 (Ross et al. 1993) or MASH at TL-3 when installed on slopes of 1V:4H or flatter, and TL-4 when installed on slopes of 1V:6H or flatter. FHWA eligibility letters must be provided to the engineer for the HTCB and its end terminals. The Materials section concludes with detailed specifications for each of the separate elements (e.g., cable, posts, fittings, reflective sheet- ing, and concrete. Prior to cable barrier installation, the name, telephone number, e-mail address, and a resume of the manufacturer’s representative assigned to the project must be provided to the engineer. This individual must be employed by the cable barrier manufacturer. The contractor is prohibited from acting in this capacity. The engineer has the right to reject a manu- facturer’s representative if he fails to demonstrate thorough knowledge of the system being installed or fails to comply with the special provision. The representative must travel to the project site to inspect the installation and discuss any issues that arise when so requested by the engineer. He must also meet on site with the engineer no later than 5 days after initial cable tensioning to inspect the entire installation. Any devia- tions from manufacturer’s specifications must be reported directly to the engineer. Under Consultation and Training, the special provision states that [T]he manufacturer must provide training with respect to the design, installation, operation, and maintenance of the cable bar- rier system. Training and consultation must be at a location in the State of Michigan deemed acceptable by MDOT. The manu- facturer must issue a dated certificate to each individual that has undergone formal training. Prior to installation of the cable bar- rier system, provide written certification from the manufacturer to the Engineer that the entire work force to be used for installing the system has received the training and necessary aids to install the system. This work force training must include installation of the foundations, end terminals, posts, cables, turnbuckles, reflectors, miscellaneous hardware, and tensioning the cables. The written certification must contain a list of individuals trained and certified by the manufacturer. As noted previously, Michigan DOT has a separate Spe- cial Provision for Training and it requires the manufacturer to conduct a minimum of four training sessions. Session 1 is intended primarily for maintenance forces, emergency first responders, and tow truck operators. This training session is conducted in an office or classroom setting prior to cable bar- rier installation, unless otherwise specified by the engineer. It addresses issues such as safely removing vehicles caught in the cables and a list of actions that should or should not be taken after an impact. Session 2 is primarily for construction and maintenance forces and is held in a classroom setting. This session covers basic maintenance such as tensioning MICHIGAN Michigan DOT has developed the most comprehensive series of Special Provisions addressing HTCB. In addition to a basic Special Provision covering HTCB in general, the state has separate documents for HTCB Spare Parts and Repairs During Construction, Maintenance, and Repair of HTCB After Con- struction, HTCB Training Sessions, and Removing, Salvaging, and Reconstructing HTCB. Although the Special Provision for HTCB addresses the items contained in many state specifications or special provi- sions, generally in much greater detail, it also includes items that may be unique to Michigan. The specific categories include: • Description • Materials • Manufacturer’s Representative • Consultation and Training • Plans and Shop Drawings • Geotechnical Information • General HTCB System Design • Concrete Foundation Construction • HTCB Construction/Installation • Cable Terminal Foundation Monitoring • Measurement and Payment. The Description states that the “work consists of construct- ing high-tension cable barrier (HTCB) as shown on the plans, (and) according to the manufacturer’s details and specifica- tions, and this special provision. If the requirements of this special provision conflict with the requirements of the manu- facturer’s details, comply with the requirements of this special provision.”

22 the cables, splicing them when necessary, use of the tension meter, and any other specialty tools that may be needed for the system. Session 3 is for the same participants from Ses- sion 2 and consists of hands-on training at the installation site and gives each person the opportunity to splice cables, adjust tension, and to perform other tasks needed for barrier repair, as well as for routine maintenance. Session 4 requires training for repairs to the system during cold weather. It is conducted on site when practicable, but may be presented to maintenance forces in a classroom setting. Plans and Shop Drawings must be submitted in paper and electronic format to the project engineer, the Michigan DOT Regional Soils Engineer, Construction Field Services Engi- neer, Operations Field Services Division, and the Design Division at least 30 days before barrier installation. Each set of plans must include detailed shop drawings of the cable system, design calculations and notes, and any construction specifications. The drawings for each cable run must include cable heights, post lengths (total and above ground), post spacing, detailed drawings of all posts and hardware, turn- buckle locations, overall barrier length, end terminal design and locations, and foundation design. The end terminal foundation design must show all dimensions and steel rein- forcement layout and be signed and sealed by a professional engineer licensed in Michigan. In addition, the plans must include the following: • A report detailing the methodology and geotechnical data used to design line post foundations and end ter- minal foundations. • A table showing the recommended post spacing as a function of roadway curvature. • A table and/or a graph showing impact deflection (at TL-3) as a function of post spacing. • A table showing the recommended cable tension as a function of cable temperature. • A signed certification letter from the manufacturer indicating the cable system conforms to this special provision. • Appropriate FHWA acceptance letters for the system, including its end anchors. Limited Geotechnical Information is provided to the con- tractor by Michigan DOT and it “. . . may be used for design purposes at the manufacturer’s discretion. It is expressly understood that the Department will not be responsible for interpretations or conclusions drawn from geotechnical information furnished by the Department . . . Soil data fur- nished by the Department represent conditions at specific locations. No inference should be made that subsurface con- ditions are the same at other locations.” The contractor is advised to “contact the manufacturer prior to bidding and determine if additional geotechnical data is required.” If so, the contractor must “obtain and furnish additional geotech- nical data . . . and laboratory tests required for the manufac- turer to complete design of end terminal foundations or other components of the cable barrier system.” Under General HTCB System Design, Michigan DOT requires that the following criteria be met: • The minimum design load for end terminal and cable connections to the foundation must be based on the theo- retical cumulative cable tension expected at -25°F. • Each foundation must be designed using the P-Y Method when checking the theoretical deflection and must use the Broms Design Method when checking overturning. • Each foundation must be designed using the geotechni- cal data furnished by the department and/or the contrac- tor, as determined by the manufacturer. • A minimum factor of safety of 2.5 against overturning using the Broms Design Method must be used. • End terminal deflection must not be greater than 0.5 in. when subjected to the minimum end terminal design load described in this special provision, using a mini- mum factor of safety of 1.0 in the foundation deflection analysis. • End terminal foundations must be designed to resist uplift and/or downward forces using a minimum fac- tor of safety of 2.0 and the Beta and Alpha Methods (FHWA-IF-99-025). • Steel reinforcement must be designed using appropriate AASHTO guidelines. • Drilled shaft concrete foundations must be used for all end terminal and post foundations. A rectangular reinforced concrete cap may be used to connect two or more cylindrically shaped end terminal foundations, but it must have a minimum depth of 48 in. The section on Concrete Foundation Construction goes into significant detail on the construction specifications for all footings and foundations, including drilled shaft procedures, steel reinforcement, and concrete placement. Michigan DOT requires that the bottoms of all concrete foundations, includ- ing line post and end terminal foundations, be a minimum of 48 in. below ground level. In addition, the minimum diam- eter for all foundations is 15 in. The section on HTCB Construction/Installation basically requires that the cable barrier system be installed according to the plans, this special provision, and the shop drawings developed by the manufacturer for this project. Post spacing is limited to a maximum of 10.5 ft, unless otherwise speci- fied on the plans developed by the Department or directed by the engineer. Upon completion of the barrier, and after the concrete end anchor foundation has reached a minimum compressive strength of 3000 psi, each cable is tensioned as specified by the manufacturer, based on the cable tempera- ture. Final tensioning is required a minimum of 2 weeks after the initial tensioning and adjusted as needed. The contractor must then “submit written certification to the Engineer indi-

23 cating the date of initial cable tensioning, date of final ten- sioning, the ambient and cable temperatures on each of these dates, and the tension in the cables on each of these dates.” Michigan mandates Cable Terminal Foundation Moni- toring, requiring the contractor to furnish and install three reference markers on each end terminal foundation to moni- tor longitudinal and lateral foundation movement over time. Two control reference markers must also be installed. Initial observation is to be made within a minimum of 2 weeks after initial cable tensioning, and follow-up observations (to measure any lateral, longitudinal, vertical, and/or rotational movement) be made 12 months after the initial observations, or as directed by the engineer. All observations are required to be conducted by a professional surveyor licensed in the state of Michigan. Any end terminal foundation movement exceeding 1 in. within 12 months of final cable tensioning and resulting in any tension reduction to the cable system requires repair and retensioning of the cables at no additional cost to the department. Measurement and Payment is similar in Michigan to most other states. The HTCB is paid on the linear footage of cable barrier actually installed, exclusive of the end anchors. The end anchors are bid per each. Bid prices for the anchor blocks are based on conservative foundation designs developed by the manufacturer in conjunction with geotechnical consultants prior to bidding. Michigan does not allow any additional pay- ment for constructing cable barrier foundations with dimen- sions and/or depths different from those used by the bidder for bidding and estimating purposes. Michigan DOT’s Special Provision for High-tension Cable Barrier Spare Parts and Repairs During Construction requires the contractor to obtain a spare parts package, unique to the system selected for installation, to make repairs to any section of barrier damaged before final acceptance of the project. Any such parts not used during construction become the property of the department upon completion of the project. The Special Provision for Maintenance and Repair of High-tension Cable Barrier After Construction covers the requirements for routine maintenance of completed installa- tions and any repairs necessitated by crash damage. The con- tents of this document are similar to those in the Michigan DOT’s Special Provision for High-tension Cable Barrier insofar as materials and installation methods are concerned. However, it requires all contractors to have adequate experi- ence in maintaining each of the HTCB systems included in a contract as well as a certification letter from each manu- facturer that the contractor has received appropriate train- ing in that system. The contractor must also maintain a spare parts inventory for each of the systems that he or she will be required to maintain. In addition to repair work, the contrac- tor also conducts routine maintenance on all cable barrier runs approximately once every 12 months unless otherwise directed by the engineer. Annual maintenance includes checking and adjusting cable tension as needed, exercising and lubricating turnbuckles, repairing any damaged galvanized surfaces, and reporting any damage noted to the engineer. The contractor must receive the engineer’s authorization before initiating repair work. COLORADO Section 606 of Colorado’s Standard Specifications addresses cable barriers. Its primary categories include Description, Materials, Construction Requirements, and Method of Mea- surement/Basis of Payment. In addition to the specification, Colorado DOT has also produced a concise Cable Barrier Guide that provides a comprehensive summary of all perti- nent issues regarding the use and design of HTCB in the state. Under Section 606, the Description and Materials sections are direct: it states that the work “consists of the installation of Tensioned Cable Barrier at locations shown on the plans” and the materials must be those needed for a four cable, FHWA- approved TL-4 system that is included on Colorado DOT’s approved product list. Socketed posts and pre-stretched cables are also required. Colorado DOT Construction Requirements are similar to those of other state agencies and require that the barrier be installed in accordance with the details shown on the plans and in accordance with the manufacturer’s recommendations. Design deflection is not to exceed 9 ft and the maximum post spacing allowed is 20 ft. The contractor must be adequately trained to ensure proper installation and the manufacturer’s representative must check the completed installation, includ- ing cable tension, and provide a signed statement that all has been installed correctly and is functional. The specification requires the contractor to “conduct a soil survey based on at least one test boring every mile and at anchor sites to identify the soil type, classification, and load-bearing capacity. The Contractor shall submit the results of this soil survey to the Manufacturer so that adjust- ments can be made to the size or type of footing. A copy of this survey shall also be submitted to the Engineer for the

24 project records.” Colorado DOT requires a minimum con- crete footing size of 14 in. in diameter and 3 ft in depth for line posts. The Colorado specification also requires the con- tractor to deliver spare parts to a designated Colorado DOT maintenance facility. These parts consist of one complete end anchorage unit and all parts required for repair of 1,500 ft of barrier. Method of Measurement/Basis of Payment is again by the linear foot for the barrier proper and separate payment for each end anchor unit. Colorado does allow for additional payment for concrete if the post and end anchorage footings required based on soil borings are larger than those originally specified in the contract. tion requires a four-cable design compliant with NCHRP Report 350 TL-3 or TL-4, with a top cable height of not less than 35 in. and a bottom cable height of no more than 19 in. (Ross et al. 1993). Shop drawings and installation procedures must be furnished to the engineer at least ten days prior to installation work. This Special Provision requires that a manufacturer’s rep- resentative, or an installer who has been trained and certi- fied by the unit’s manufacturer, shall supervise assembly and installation at all times. A copy of said certification must be provided to the engineer before installation. All installation, including anchors and transitions, shall follow the manufac- turer’s recommendations. Any contractor-proposed modifi- cations to the plans must be submitted to the engineer for approval at least ten days prior to work in the affected sec- tion. Line posts shall be socketed in concrete footings in a size recommended by the manufacturer. Washington also requires the contractor to deliver spare parts for future maintenance. These include 100 line posts and associated attachment hardware, 20 sockets when steel sockets are used in the initial installation, 50 ft of cable, and three cable splices and turnbuckle assemblies (four of each for a four-cable system). A tensioning device recommended by the manufacturer must also be delivered to the state. The state has a single pay item for HTCB, per linear foot, for the entire barrier installation from end to end (including transi- tion sections, cable-to-guardrail terminals, foundations, end anchors, and all associated hardware). The additional HTCB components (i.e., spare parts) are billed as a lump sum item. WASHINGTON STATE Washington State’s Special Provision for HTCB includes a description of the work, materials, construction, additional components, and pay items. The work description requires supplying and constructing high-tension cable barrier systems, including all hardware, terminals, and transition sections in conformity with the lines and grades as staked. System selec-