DYNAMIC RESPONSES OF FRAME-SHEAR WALL BUILDINGS

Abstract

Dynamic responses of tall frame-shear wall buildings are investigated in the present study. The structure is modelled as a shear-flexure cantilever. Shear walls contribute mainly to flexural stiffness while frames to shear rigidity. Continuum approach idealizing the frames and connecting beams as a shear continuum of equivalent properties is adopted in the analysis. The presence of floor slabs which are very rigid in-plane ensures that the whole building deflects as a rigid section body. This reduces tremendously the number of degrees of freedom involved in the study of such structures. The governing differential equations of motion are separated into space and time domains through the concept of separation of variables. Galerkin technique is employed to transform the resulting differential equations in space domain to a set of algebraic equations. Both the time and frequency approaches are considered to study the dynamic responses of the building. Newmark's step-by-step integration method is adopted to trace the structural response in the time domain. The proposed method is employed to study the dynamic response of a building subjected to the El-Centro earthquake load analysed earlier by Ishak (1975). The results from the present study agree well with the published values. Dynamic response of flexible buildings under random wind loads is carried out using the frequency domain approach. The generalized wind force spectra based on available experimental data is established and compared with existing closed form solution results. Except for the torsional component, the wind force spectra generated from experimental results agree well with the published closed form solutions. The expected values of the responses of several typical tall buildings under turbulent wind loads are evaluated, presented and compared with published values when available. The proposed method with proper choice of shape functions is found to be efficient and convenient especially for preliminary design purpose.