Quantifying higher mode effects in rocking systems considering shear-flexural behavior

Strong ground motions induce tremendous energy on structures resulting considerable forces and displacements. In ordinary structures, strong seismic forces are dissipated through permanent deformations and damages in structural and nonstructural members which can lead to costly casualties, or repairs. With development of seismic control methods, researchers proposed new methods for seismic energy dissipation with minimum damages. Rocking control system is one of efficient methods where seismic energy can be dissipated using fuse elements and rocking movement. There are fundamental differences between seismic design of this system and ordinary ones due to higher mode effect phenomenon and seismic performances. Also, in the rocking system most of the structural components remain elastic to prevent permanent damages. In recent years, different approximate methods were proposed for simplifying the seismic design of this system considering higher mode effects. These methods are often based on pure shear or flexural behaviors. However, a combination of both shear and flexural behaviors is required for modeling structural performance in real condition. To fulfill this aim, this paper presents an improved method using a new parameter and considering both shear and flexural behaviors, simultaneously. The proposed method is discussed and illustrated in detail and its results are compared with those of obtained by the previous ones.