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Agencies Gain a Bridge Lifecycle Assessment Tool.


pdf icon Agencies Gain a Bridge Lifecycle Assessment Tool. (2895 K)
Ehlen, M. A.

Bridge Builder, February/March 1999.

Keywords:

bridges (structures); design applications; building economics; construction materials; life cycle costing; new technology materials

Abstract:

State departments of transportation (DOTS) are currently in the difficult position of having backlogs of bridges to repair and increasingly smaller budgets. Nationally, these repair costs are large, totaling as much as $90 billion, according to one report. Consequently, many of these agencies are looking for ways to make their bridges less costly to build and longer lasting. New construction materials - such as high-performance concrete (HPC), FRP composites, high-performance steel and new applications of wood and aluminum - show promise toward reducing the sum of a bridge's construction, maintenance/repair, and disposal costs, also known as its "life- cycle" cost. Their technical performance can be verified using standard methods, but agencies still need a tool for assessing the lifecycle cost effectiveness of the materials. The National Institute of Standards and Technology (NIST) has recently completed the beta version of BridgeLCC, a Windows lifecycle costing software program for bridge engineers. Based on ASTM Practice E 917 for measuring the lifecycle costs of buildings and building systems, BridgeLCC provides a standardized, user-friendly tool for comparing the lifecycle costs of alternative bridge materials and bridge designs. The software is designed to accommodate new construction materials but works equally well for comparing conventional materials. The program begins with bridge costs that are most familiar to engineers: the "engineer's estimate" of initial construction costs. When making a preliminary design of a new bridge, engineers typically estimate the construction costs of two or more alternative designs, such as a concrete-beam design versus a steel-beam design. BridgeLCC allows the user to input the engineer's estimate for each alternative and then the remaining costs in the ASTM Practice - operation, maintenance, and repair (OM&R) and disposal costs. Using an NIST cost classification scheme, engineers also can enter user costs and third-party costs. User costs are inccurred by automobile drivers on and under the bridge, and third-party costs are incurred by third parties who are not direct users of the bridge but are affected by bridge construction activities, such as lost revenues of businesses whose customers are blocked by brdige work.