EVALUATION OF EXPERIMENTAL LOAD RATING OF POSTED BRIDGES

Bridges are traditionally rated based upon a non-site specific calculation of the bridge's load-carrying capacity. Even if an advanced analysis of the bridge is performed, such as a finite element analysis, many sources of capacity are too bridge-specific to be included without field experimentation. These specific sources of capacity are often sufficient to allow a bridge that would be posted at a severely low level to be posted at a higher level or not posted at all. Experimental load rating provides a method for quantifying these sources of strength for individual bridges and incorporating them into the rating process. An experimental load rating is performed by applying a load to the bridge in the field and measuring its response. The measured responses are either used to directly assess the capacity of the bridge (proof testing) or are used to refine the analytic model of the bridge (diagnostic testing). A review of the available literature on experimental load rating is the emphasis of this report. The different test techniques, instruments, and associated costs have been evaluated.