Steel building response under biaxial seismic excitations

In the paper the effects of the bi-directional input ground motion on a six story steel moment resisting frame building, designed according to EC3 and EC8 provisions, are evaluated. Some response parameters, obtained considering only the "primary" horizontal component of a real earthquake acting on a principal direction of the building, are compared to the ones obtained when the "secondary" horizontal component, acting on the orthogonal direction, is added. Nonlinear analyses are performed using five real earthquakes. The action of the secondary component does not increase the maximum top floor displacement and the interstory drifts in the direction of the primary component, while a low increment is obtained considering their vectorial values. On the contrary the column cross-section damage is much increased.