BRIDGE LOAD RATING USING PHYSICAL TESTING

This paper describes a current attempt to evaluate and document the applicability, ease-of-use and accuracy of a system for load rating of bridges through physical testing. Results from the load rating of one bridge are presented to illustrate the use of the physical load testing. A typical bridge in the project was instrumented with 40 strain transducers and tested with known loads using a commercially available system. Several finite element models of the bridge were then developed and calibrated based on the observed behavior and the field measured strain. Results from the calibrated model were then used to carry out load rating calculations that were then compared to traditional rating calculations. The resulting ratings showed a general increase over the traditional codified ratings. For the subject bridge, various configurations of strain gauges were investigated with respect to general influence on modeling and rating accuracy. The girders for this bridge were found to act non-compositely and very little edge stiffening was present. Commercial systems were found to be effective tools to implement the testing, modeling and rating of existing bridges. Although developing load ratings through diagnostic testing costs more than load ratings by traditional hand calculations, these costs may be offset by the long-term savings that result from extending a bridge's service life.