The combination of seismic and vehicle live loadings on bridges is an important design consideration. There are well-established design provisions for how the individual loadings affect bridge response: structural components that carry vertical live loads are designed to remain well within the linear-elastic range while lateral load carrying components are designed to yield under large seismic excitations. The weight of the bridge superstructure is taken in to account as dead load in structural analysis for seismic loads; however, the effects of additional mass and damping of live loads on the bridge deck are neglected. To improve the design of highway bridges for multi-hazard effects of seismic plus live load, many questions arise and are addressed in this project via numerical simulations of short span bridges. Further extensions of this research can be extended to long span bridges whose seismic response is more heavily influenced by vehicle mass on the bridge deck.