TRUCK LOADS ON SELECTED BRIDGES IN THE DETROIT AREA

Abstract

Several bridges in the Metropolitan Detroit Area show signs of serious deterioration. In particular, spalling concrete can be observed, which may cause accidents or other traffic problems. In order to correct this situation, a considerable number of bridges must be evaluated to determine actual strength and predict remaining life. This involves the measurement of truck weights and strains in bridge components. The recorded parameters include axle loads, axle spacings, vehicle speed, and vehicle position (right or left lane). The system is not visible to the bridge users, which results in unbiased traffic measurements. The strains are collected and processed using the rainflow algorithm, which is the accepted method for fatigue analysis. The results can be used to determine component-specific load effects, load distribution factors, and fatigue load spectra. The overloaded fatigue-prone components can then be identified and subjected to a more rigorous field inspection. This progress report summarizes measurements completed on two bridges in 1993 and presents the format for a future final report. Bridge weigh-in-motion (BWIM) data are presented for the bridge on Wyoming Road over I-94 in Detroit. Fatigue strain data are presented for the bridge on US-23 southbound over the Saline River in Monroe County.