Practical Modal Pushover Design of one-way asymmetric-plan reinforced concrete wall buildings for unidirectional ground motion

Abstract

This paper presents a new displacement based seismic design method called Practical Modal Pushover Design (PMPD). The method is applied to multistory one-way asymmetric-plan RC wall structures. PMPD combines concepts from Direct Displacement-Based Design with an inverse version (formulated herein) of Practical Modal Pushover Analysis (PMPA). PMPD generates designs which achieve peak deformations exactly equal to the governing deformation limits when analyzed with PMPA. An alternative method, Modal Pushover Design (MPD), which is, to some extent, an inverse version of Modal Pushover Analysis, is also discussed. MPD is computationally more demanding than PMPD, but has improved performance in cases where yielding may occur due to ‘higher mode’ response. Advantages of PMPD include explicit consideration of nonlinear, torsional and ‘higher mode’ effects. Iteration is limited to the response spectrum level, so multiple analyses of Multi-Degree of Freedom systems are not required. Capacity design principles are implemented directly from the start of the design process. A significant advantage of PMPD is that the engineer can have the same confidence in the structure’s seismic performance as he has in PMPA’s ability to predict the structure’s peak seismic responses. Therefore PMPD can be used for the seismic design of any structure for which PMPA is expected to provide acceptably accurate predictions of peak seismic responses. The effort required to carry out PMPD is similar to that required for PMPA. The only additional work consists of specifying a relative flexural strength distribution and executing a small number of iterations at the Single Degree of Freedom level.