Parametric study of rocking cores-moment frames with supplemental viscous damping and self-centering devices using a distributed parameter model

Abstract

A distributed parameter model is proposed for the rocking cores-moment frames (RCMFs) with supplemental viscous damping and self-centering devices. In this model, the moment frame and rocking cores are simplified as a shear beam and a flexural beam, respectively, while viscous damping and self-centering devices are substituted by rotational constraint with linear viscous damping and elastic stiffness. Three nondimensional parameters, frame-core stiffness parameter, base-rotation fixity parameter and damping parameter, are introduced to describe the dynamic behavior of the full physical structural system. Closed-form solutions for complex modal shapes are derived, and then parametric study is conducted to explore the effects of these three parameters on modal damping ratios, eigenvalues, complex modal shapes, and drift concentration factor. Explicit expressions of modal damping ratios with these three parameters are established through curve-fitting technique that can be conveniently used for engineering practice. Frequency responses of base shear forces and moments are obtained using the distributed transfer function method. It is concluded that the modal damping ratios are significantly affected by these three parameters, and their peak values will be remarkably reduced as the increasing of the frame-core stiffness and base-rotation fixity. For design purpose, appropriate ranges of these three parameters are recommended to achieve better drift uniformity control, response reduction, and higher modes effect mitigation. The proposed model and conclusions of the parametric study can be used as a tool for rapidly evaluating seismic performance in a preliminary design phase of the RCMFs.