Lateral Live-Load Distribution Characteristics of Simply Supported Steel Girder Bridges Loaded with Implements of Husbandry

This paper discusses the effect of agricultural live-loads on lateral load distribution characteristics of girder bridges on rural roadways in the United States. In this study, load distribution factors for bridges subjected to agricultural vehicles frequently used on rural roads are calculated based upon codified processes, field test results, and simulations. As part of this work, five simply supported steel girder bridges in Iowa were selected for field tests with four agricultural vehicles and a highway-type truck. Strain sensors were mounted on the bottom flanges of girders at midspan of all five bridges. Strain data resulting from the test vehicles were measured and used to determine girder distribution factors for each bridge. These strain data were also used to calibrate analytical models of the bridges. Over 120 agricultural vehicles were identified and used to analytically load the models. Girder distribution factors were then computed using responses from the vehicle-induced model simulations. Findings revealed that the analytical and field distribution factors were in most cases smaller than code-specified values, as has been observed by others. In some cases, however, these factors exceeded code values. Furthermore, the variability in agricultural vehicles' characteristics had a significant impact on the live-load distribution factors for each bridge.