TRUCK LOADS ON SELECTED BRIDGES IN THE DETROIT AREA. RESEARCH REPORT

The project is focused on structures that showed signs of deck deterioration, in particular spalling concrete. The selection criteria included location, accessibility for testing equipment, span length, truck traffic volume, and presence of stop lights. The results of measurements are available for seven bridges. In general, live load on bridges is strongly site specific. There is a considerable variation in traffic volume and weight of trucks. The estimated average daily truck traffic (ADTT) varies from 500 to 1,500 (in one direction). The maximum observed truck weight varies from 80 kips to 250 kips. The maximum observed axle weights vary from 20 kips to almost 50 kips. The largest GVW and axle weights were observed on I-94 and M-39. These roads also have the largest observed traffic volume with the estimated ADTT up to 1,500 in one direction. The observed truck weights are compared with estimated Michigan legal limits. Most of the overloaded trucks were observed on high-volume highways (I-94 and M-39). The actual percentage varies depending on the number of axles, from 0 to 40%. The largest percentage of overloaded trucks was observed for 11-axle vehicles. For each bridge, the results are shown for all truck types together, and then separately for each truck type (by number of axles). The presented data include histograms and cumulative distribution functions (CDFs) of the gross vehicle weight (GVW) and axle weight.