WIM-based state-specific live load spectra for Alabama

Abstract

The knowledge of the actual live load is important for a rational management of highway structures. The forms of damage due to live load include fatigue cracking, formation of pot- holes, excessive vibration and deflection and in extreme cases even a catastrophic collapse. It has been observed that traffic load is strongly site-specific. There are considerable differences in traffic volume and weight of trucks. Recently, a substantial data base has been collected using Weigh-in-Motion (WIM) stations. The objective of this paper is to review the available WIM data for the State of Alabama and assess the degree damage in highway bridges depending on traffic volume (ADTT) and weight of heavy vehicles. The cumulative distribution function (CDF) of the gross vehicle weight (GVW) is considered separately for different locations, years and classes of vehicles. The live load effects are calculated using influence lines of moments and shear forces for a wide range of span length. The results are plotted on the probability paper for an easier interpretation of the results. For the considered locations, the percentage of overloaded vehicles is determined to facilitate a site-specific comparison. The present study confirmed that for each WIM location, it is possible to pin-point which types of vehicles have a major contribution to bridge damage.