Add to ORKGA research was recently granted by the Italian Government to develop a comprehensive procedure to account for spatial variability of ground motion as well as soil-structure interaction in assessing the behaviour of bridges. This paper reports on the work-package relevant to the effects of soil-structure interaction. In the first section, a methodology to include the effects of soil-structure interaction in the nonlinear response of bridges is presented. Kinematic interaction analysis is performed in the frequency domain by means of a procedure accounting for radiation damping, soil-pile and pile-to-pile interaction; the non-linear inertial interaction analysis is performed in the time domain by using a finite element model of the superstruc...