Report No.: CCEER-89-3

Authors: Arya Ebrahimpour and Puttanna Jagadish

Date: December 1989

A Report to the:

Research Advisory Board

University of Nevada, Reno

Summary and Conclusions

The goal of this study was to statistically model the bending moments induced in medium span bridges due to various loading configurations of trucks in the state of Nevada. We assumed that the bridges were simply-supported and that they consisted of two lanes with traffic in both lanes travelling in the same direction. A Monte Carlo simulation computer program was written to use the data provided by the Nevada Department of Transportation and generate sufficiently large random samples of truck loading events.

Despite the assumptions made in the current bridge specifications and current literature, we observed that the two-axle single unit trucks comprise a major portion of the truck traffic in Nevada; thus we incorporated this latter type of truck as well as two other dominant types of trucks in our study. The corresponding maximum bending moments were calculated by multiplying the randomly generated moving loading configurations by the bridge moment influence function at discrete locations along the bridge length.

Statistical curve fitting of the generated random sample were performed using three probability distribution types. Using the statistical goodness of fit test, we found that a gamma distribution best describes the truck loading in medium size bridges in Nevada (Summary and conclusions by authors).