Treatment of P-Δ effect in a displacement-based design procedure of steel moment resisting frames

The present work studies the P-Delta effect in the framework of a direct displacement based design procedure for steel moment resisting frames. A simple formula for the yield displacement amplification factor as a function of ductility and the stability coefficient is derived on the basis of the seismic response of a single degree of freedom system taking into account the P-Delta effects. Extensive parametric studies result in a simple formula for the stability coefficient as a function of the number of bays and stories of a steel frame. Thus, the P-Delta effect can be easily taken into account through the stability coefficient and the yield displacement amplification factor.