MAHMOOD HOSSEINI - Lifeline Earthquake Engineering Department, international Institute of Earthquake Engineering and Seismology (IIEES), P.O.Box ۱۹۳۹۵-۳۹۱۳, Tehran, IRAN

The effect of earthquake directionality on the seismic response of highway and railroad bridges has been emphasized by some researchers in recent years, But there are few works on the study of this effect in the case of multi-component excitations, specially by considering the combination of vertical and horizontal ground motions. In this paper, by applying two-and three-component accelerograms of some well-known earthquakes, the linear and nonlinear response of a number of bridges, including both highway and railway bridges, have been investigated. Most of usual structural systems for bridges including truss, moment frame with both simple supports and built-in connections, and also slab on arch, constructed with steel, reinforced concrete, as well as composite material have been considered in this study. The numerical results indicate that in the case of multi-component excitations the earthquake directionality can affect the values of internal forces in some of bridge elements even up to ۵۰%.