  The present paper assesses the efficacy of code live-load models in
accurately estimating the vehicular loads transferred to bridge substructures,
such as abutments, piers, and foundations. Realistic traffic vehicle data are
represented using four Weigh-in-Motion databases, which provide an authentic
representation of vehicle information, thus providing a realistic basis for the
examination of the bridges studied. The evaluation includes various bridge
models, such as single-span girder bridges and two-, three-, and four-span
continuous pinned-support girder bridges. By analyzing exceedance rates, the
study compares the extreme force values obtained for vehicles in the databases
with those predicted by selected code live-load models. These exceedance rates
are presented in spectra format, as a function of the span length. The
significant variations observed in the exceedance rates highlight the need for
improving existing code live-load models to achieve more accurate estimations
of the forces transferred to bridge substructures. Such improvements would lead
to more uniform reliability levels for any limit state, such as resistance,
fatigue, serviceability, and cracking.
