Development of experimental influence lines for bridges
Date
2006
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Publisher
University of Delaware
Abstract
Ongoing deterioration of the nation's bridge inventory, combined with limited financial resources for maintaining it, makes the role of bridge management more important than ever. In order to effectively manage a bridge inventory, bridge owners need to know the condition of their bridges. It has been shown that calculation of a bridge's load carrying capacity using as-built details and standard design equations most often under predicts the bridges actual capacity. While it is understandable that design equations will yield conservative designs, when making bridge management decisions, owners desire to have accurate condition assessments. One effective method for evaluating a bridges current condition and load carrying capacity is through the use of field load tests. An ideal field test would be conducted with minimal instrumentation, minimal traffic interruption, and commonly available load vehicles. In this thesis, a method for developing experimental influence lines using field test data is developed. The influence lines produced are well suited for use in quantifying how a particular bridge distributes loads, and can also be used to estimate the load carrying capacity of the bridge. Test procedures for short to medium span bridges, that utilize strain transducers and dump trucks and that are similar to those used for diagnostic tests, are developed. Also developed is the methodology of determining influence lines from the experimental data. Using the methodology developed, the procedure is applied to the South Market Street bridge in Wilmington, Delaware. Experimental influence lines that are developed for this bridge are used to evaluate the load distribution to the floor beams of the bridge, and can be also be used by the bridge owner to evaluate the safety of the bridge to carry multi-axle super loads.