Sensitivity of bridge health index to element failure costs and conditions

Abstract

The Bridge Health Index (BHI) is a bridge performance measure based on the condition of the bridge elements. It is computed as the ratio of remaining value of the bridge structure to the initial value of the structure. Since it is expressed as a percentage value, the BHI could provide an intuitive measure for bridge engineers, and legislators. The BHI could be converted to another measure such as color (red, yellow and green) that the public understands better. The Pontis user group was surveyed to determine the current use of the BHI and other measures for bridge management decision making. This study focused on understanding the sensitivity of the BHI to small and large changes in the element failure costs and the element condition, the two input data sets for computing the BHI. For these sensitivity analyses, 221 bridges were selected from Wisconsin?s inventory. The study looked at bridges with simple and continuous span prestressed concrete girders. The findings can guide state agencies and practitioners with a sense of how BHI responds to changing bridge condition as well as element failure costs. The element failure costs were acquired from a previous study by a consultant to the FHWA and the element level inspection data were from the Wisconsin Department of Transportation (WisDOT). The analysis considered the impact of Smart Flags used to identify local problems that are not reflected in the element condition states. Because they may indicate critical defects in the bridges, they should be reflected for BHI. To investigate the impact of Smart Flags, computation rules suggested by the Kansas DOT were applied to the selected bridges in Wisconsin.