Comparison of different design requirements on P-delta effects for steel moment resisting frames

Steel moment resisting frames (MRFs) compliant with EN1998-1 are largely overdesigned owing to the need to satisfy the severe requirements for lateral deformability and P-Delta effects. On the contrary, the North American codes (e.g. ASCE7) introduce different rules to consider the structural sensitivity to the P-Delta effects. In lines with the latter approach, the current draft version of the amended EN1998-1-1 introduces a different methodology to account for the structural lateral displacements. This work aims to investigate, using static nonlinear analysis, the effectiveness of the new EC8 provisions with respect to the former version of EC8 and the current ASCE7. The analyses have been carried out by accounting for the real dimension of beam-to-column joints and their behavior, which was simulated by means of a non-linear spring, properly calibrated against experimental tests. The results show that the structures designed according to the latest draft version of the EN1998-1-1 and those compliant with the North American code have a similar behavior.