ABSTRACT

The objective of this study is to determine the actual truck loads on US highways. The need for reliable truck weight data has been recognized by many State DOT’s and the Federal Highway Administration (FHWA). For many years, trucks were measured at a limited number of stationary scales (truck weigh stations) that are located on major highways. However, there is a justified concern that the heaviest trucks knowingly avoid the scales [3] and as a result the weigh station data is biased to less heavy vehicles. Accurate representation of the actual load spectra on State and Federal highway bridges will reduce the uncertainty in the evaluation of bridge load carrying capacity, prediction of deterioration (corrosion) rates and bridge remaining life (fatigue). The development of the Load and Resistance Factor Design Bridge Design Code [1] was based on a truck survey at a site in Ontario in 1975 which consisted of 9,250 trucks that appeared to be heavily loaded [4]. This relatively limited dataset is now 30 years old and, given the continuous change of the trucking industry, these statistics have undoubtedly changed. In this study, a statistical basis is developed for the live load model for bridges in the State of New Jersey. Major load parameters that affect bridge design and evaluation (i.e. truck volume, type and weight) are considered. The database consists of truck load information collected from 33 WIM sites located throughout the State of NJ over an 11-year period (1993-2003).