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Chapter 7
Bridge Maintenance

Bridge construction and rehabilitation projects are complicated by the environmental sensitivities of working in riparian areas, including restricted work times to accommodate spawning periods of various aquatic species.

The majority of the steel bridges in the interstate highway system were constructed between 1950 and 1980; up until the mid 1970s, virtually all steel bridges were protected from corrosion by three to five thin coats of lead and chromate containing alkyd paints, creating dramatic complexity and cost increases for major and routine level bridge paint maintenance. [N] Lead-based paint abatement and the related issues of environmental, worker, and public protection came to the forefront of the maintenance painting industry in the mid-1980s to early 1990s when regulations on hazardous waste disposal and lead exposure to workers were promulgated by EPA and the Occupational Safety and Health Administration. The changes wrought by these rules still shape the direction of maintenance painting in the bridge industry. [N]

NHI has developed a training course, " Hazardous Bridge Coatings: Design & Management of Maintenance & Removal Operations - NHI Course # 13069" for FHWA and State bridge engineers in the area of bridge coatings maintenance and specification. This course includes guidance on coatings selection, surface preparation specification, and environmental and worker safety issues and covers some of the information in a number of the following sections. [N]

In addition to coatings and coating removals, bridge maintenance activities include repairing bent or damaged steel beams, cracked or spalled concrete, damaged expansion joints, and bent or damaged railings. These activities can entail operation of support vehicles and equipment, pavement repair, welding and grinding operations, and associated pollutants. Environmental stewardship practices under paving, structural pavement failure (digouts), pavement grinding, and concrete slab and spall repairs may be pertinent for bridge repairs.

 

7.1. Preventative Bridge Maintenance Practices

Preventative bridge maintenance avoids larger scale work in stream environments, and thus makes sense from the standpoint of stewardship of both natural and financial resources. Preventive maintenance is defined as a planned strategy of cost-effective treatments applied at the proper time to preserve and extend the useful life of a bridge. Bridge maintenance encompasses:

  • Cleaning activities, including annual water flush of all decks, drains, bearings, joints, pier caps, abutment seats, concrete rails, and parapets each spring.
  • Preventive maintenance activities such as painting, coating and sealant applications and for routine, minor deck patching and railing repairs.
  • Technical and specialized repairs, including jacking up the structures, crack repairs, epoxy injection, repairing or adjusting bearing systems, repair and sealing of expansion joints, repair or reinforcement of main structural members to include stringers, beams, piers, pier and pile cap, abutments and footings, underwater repairs, major deck repairs, and major applications of coatings and sealants.
  • Stream channel maintenance including debris removal, stabilizing banks and correcting erosion problems.

 

7.1.1 Life Cycle Decisionmaking and Accounting for Ecological Risks
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Transportation Asset Management is driven by policy and performance and considers alternatives and trade-offs, evaluating competing projects and services based on cost-effectiveness and anticipated impact on system performance. As such it employs systematic, consistent business processes and decision criteria and makes good use of information and analytic procedures. [N]

In order to maintain and repair bridges within limited budgets, DOTs are establishing procedures for early detection of problems, timely repair, good preventative maintenance routines, and consideration of long term effectiveness of dollars spent. [N] NCHRP Report 483-Bridge Life Cycle Cost Analysis. Part one establishes guidelines and standardizes procedures for conducting life-cycle costing. Part two is the guidance manual for using the software to evaluate maintenance, repair, and new bridge alternatives. The AASHTO bridge management software, Pontis, can be used to: inventory elements of a bridge (such as coated steel girders); run deterioration and cost models to determine long term preservation policies; determine preservation needs and schedules; and provide network-level performance measures.

European models have gone further in incorporating environmental aspects. The LIFECON Life-Cycle Management System (LMS) is a European model of a predictive and integrated LMS for concrete infrastructures, on both a short term and a long term basis, developed to facilitate decisionmaking. The system is divided into three levels of structural hierarchy: component and module, object, and network, with component- and module-level systems that address structural components such as beams and columns and their combinations in modules. The object-level system deals with complete structures or buildings. The network-level system treats networks of objects such as stocks of bridges or buildings. Besides a structure's observed condition and evaluated urgency of repair, the life-cycle costs, user costs, minimum requirements of structural performance, structural risks, traffic and other operational requirements, aesthetics, environmental risks, and ecological pressures can be taken into account for multiple-attribute planning on all hierarchical levels of the system. The life-cycle analysis and optimization module involves the data applications for studying the economy of the life cycle and cost-effectiveness of optional maintenance, repair, and rehabilitation strategies. Alternative strategies are compared as life-cycle activity profiles over a defined time frame. The purpose of life-cycle analyses is to find the optimal activity profiles to reach the targets. [N]

In January 2002, FHWA announced that Highway Bridge Replacement and Rehabilitation Program (HBRRP) funds can be used to perform preventive maintenance on highway bridges. Preventive maintenance activities eligible for funding include sealing or replacing leaking joints; applying deck overlays that will significantly increase the service life of the deck; painting the structural steel; and applying electrochemical chloride extraction treatments to decks and substructure elements. FHWA is currently in the process of clarifying language and restructuring the National Bridge Inspection Standards. [N] Proposed changes will reorganize the standards into a more logical sequence and make them easier to understand for inspectors, and state and federal highway administrators.

Bridge Inspection and " Smart Bridges " for Preventative Maintenance

In order to conserve fiscal and natural resources and ensure safety, DOTs are investing in bridge inspection for preventative maintenance and "smart bridges" that may forestall larger construction projects in and adjacent to streams. An increased emphasis on bridge safety and more rigorous inspection protocols followed the December 1967 collapse of a bridge over the Ohio River near Point Pleasant, WV, which claimed more than 50 motorists' lives. As a result of the incident, Congress began to require the inspection and inventory of all bridges on the National Highway System, with a specific provision that each bridge's load-carrying capacity be determined. More than 40 state DOTs and 100 engineering consulting firms now use the Bridge Rating and Analysis of Structural Systems (BRASS) software suite developed by the Wyoming DOT. Programs within the BRASS suite now include applications specific to steel, timber and concrete girders, steel girder splices, piers, trusses, culverts, and poles, as well as for illuminated signs and signals. The culvert design portion of the package comes from the North Carolina DOT; pre-stress girder design from Kansas; steel-field splice design from Nebraska; pier analysis and design program work by the Portland Cement Association, Georgia DOT and Montana DOT; truss rating from New York; and, cantilever pole analysis and design from Louisiana. [N]

FHWA's Construction and Maintenance Fact Sheet on Bridge Preservation identifies best practices in bridge preventative maintenance, highlighting PennDOT's program. [N] PennDOT maintains the third largest number of State bridges in the Nation, spending $300 million on 250 bridge projects each year. To keep costs down and ensure safety, PennDOT has found that it is vital to have both proper and frequent inspections and a good preventive maintenance program. PennDOT's team of 50 bridge inspectors and numerous other consultant inspectors inspect all of the agency's bridges at least once every two years. The bridge data is then stored in a management system, allowing engineers to prioritize the maintenance and rehabilitation needs and make sound decisions as to how to best take care of the bridge infrastructure. Handheld electronic data collection tools are augmenting such management systems and the efficiency of bridge inspection. The Pennsylvania Turnpike Commission (PTC) had a consultant develop and use a handheld data collection system for the National Bridge Inspection Standards (NBIS) inspections for more than 800 bridges on the Pennsylvania Turnpike. Over a four year period of routine inspections, contrasting handwritten reports and electronic data collection, inspectors and the PTC found the electronic reporting system reduced costs, improved quality assurance and quality control, and provided easier access to inspection information. [N]

Connecticut DOT has been using electronic monitoring systems to keep tabs on the condition of some of its bridges. Systems of linked sensors provide data on structural integrity and wear, and contribute to bridge life and stress assessment data. Portable and continuous systems have been installed on 11 bridges since 2002, allowing for early repair in sites that need it, and saving an estimated $2.7 million. [N] Likewise, high-tech optical sensors embedded in concrete beams in a bridge in Las Cruces, N.M. relay information to New Mexico State University researchers about the performance of the bridge's design and materials, letting them track structural soundness as the bridge ages. [N]

Recent research has concluded that truck weight is one of the most significant factors in the repair and replacement life of bridges. [N] TRB Special Reports 225 and 227, Truck Weight Limits: Issues and Options and New Trucks for Greater Productivity and Less Road Wear: An Evaluation of the Turner Proposal, respectively, noted that trucks produce significant damage to highway bridges. A truck's gross weight, axle weights, and axle configuration directly affect the useful life of highway bridge superstructures. Damage typically occurs in the bridge deck and in the superstructure elements including floor beams and girders, diaphragms, joints, and bearings. Bridge costs associated with increased truck weights are the result of the accelerated maintenance, rehabilitation, or replacement work that is required to keep structures at an acceptable level of service. [N] [N] [N] While prestressed concrete I-girder bridges and modern steel-girder bridges could withstand a 20 percent increase in truck weight, such an increase would reduce the remaining life in older steel-girder bridges by up to 42 percent. [N] The "smartest" bridge to date, in terms of density of sensors, is under construction in Star City, West Virginia; it contains 770 sensors, 28 data-collection boxes, and a central data processing unit. [N] WVDOT is counting on the investment to "help the state make smaller, less costly repairs while problems are still manageable," said Deputy Commissioner Norman Roush, as well as conserve resources that may be spent through overdesign. [N] Engineering data collection will be able to be correlated with continuous environmental data collection on-site. West Virginia' existing "smart" structures have already yielded valuable information, such as that concrete slabs 20 feet long are prone to cracking, while those 15 feet long are not.

Small Bridge Maintenance Activities that Can Eliminate the Need for Larger In or Over-Stream Work Projects

Some of the bridge maintenance activities that provide the biggest benefit for the smallest level of investment generally include:

  • Eliminating deck joints in old bridges
  • Repairing or installing new expansion dams on bridge decks
  • Repairing bridge decks
  • Maintaining proper deck drainage
  • Restoring or replacing bridge bearings
  • Repairing or replacing bridge approach slabs
  • Repairing bridge beam ends and beam bearing areas
  • Bridge painting

Successful control of pollution from bridge maintenance and repair involves minimizing the potential sources of pollutants from the outset.

 

7.1.2 Maintaining Drainage from Bridge Decks
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Effective bridge deck drainage is important because deck structure and reinforcing steel is susceptible to corrosion from deicing salts; moisture on bridge decks freezes before surface roadways, hydroplaning can occur more easily; and drainage occurs over environmentally sensitive areas. Bridge deck drainage is often less efficient than roadway sections because cross slopes are flatter, parapets collect large amounts of debris, and drainage inlets or typical bridge scuppers are less hydraulically efficient and more easily clogged by debris. Because of the difficulties in providing for and maintaining adequate deck drainage, the following practices should be used: [N]

  • Gutter flow from roadways should be intercepted before it reaches a bridge.
  • Zero gradients and sag vertical curves should be avoided on bridges.
  • Runoff from bridge decks should be collected immediately after it flows onto the subsequent roadway sections where larger grates and inlet structures can be used.

 

7.1.3 Bridge Cleaning
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Bridge cleaning consists of cleaning all bridge components that are susceptible to dirt, debris, bird dropping and deicing salts. Drainage systems and components subject to dirt or bird droppings accumulation need to be cleaned regularly by hand tools, air blasting or preferably water flushing.

  • Dust or any material that could be inhaled should be avoided by the use of a proper respirator.
  • Other components such as bare concrete decks, pier caps, abutment seats, bearing systems, non-sealed or open expansion joints, joint drainage troughs, head walls, wing walls, select beam flanges, truss joints etc. should receive a thorough water flush every spring (after applications of deicing salts have ceased) as a bare minimum.
  • Personnel should become familiar with various types of bearing devices. Mechanical bearing devices should be lubricated after cleaning to prevent rusting and assist in their movement.
  • Clearing of weeds, float debris, brush and overhanging limbs from the vicinity of the bridge should be performed according to best practices in channel maintenance.

 

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Continue to Section 7.2 »
 
Table of Contents
 
Chapter 7
Bridge Maintenance
7.1 Preventative Bridge Maintenance Practices
7.2 Avoiding and Minimizing Impacts to Fish and Wildlife
7.3 Enhancements to Bridges and Stream Access
7.4 Bridge Painting/Coating/Sealing and Containment Stewardship Practices
   
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