Estimation of period of vibration for concrete shear wall buildings

Abstract

Most seismic design codes generally provide formulas to be used for the estimation of the base shear and lateral loads. For the determination of the lateral loads, it is required to estimate first the fundamental vibration period of the building theoretically or experimentally (Uniform Building Code (UBC-1997); Structural Engineers Association of California (SEAOC-1996); Egyptian Code for Computation of Loads and Forces in Structural and Building Work (EGC-2012); Applied Technological Council, 1978).In various codes such as the current United States (US) and Egyptian building codes and also in the recommendations of many researches, empirical period formulas for concrete shear wall buildings relate the building fundamental period of vibration (T) to the building overall height (H). In this paper, using the available data for the fundamental vibration period of reinforced concrete shear wall buildings measured from their motions recorded during eight California earthquakes, improved formulas for estimating the fundamental period of vibration (T) of concrete shear wall buildings are developed by regression analysis of the measured period data. The results indicate that the value of coefficient Ct in the current US and Egyptian building codes formula should be decreased from its present value 0.02 to 0.014. Also, factors to limit the period calculated by rational analysis, such as Rayleigh’s method, are recommended in this paper. Comparisons between the periods determined using the proposed formula and the measured values show good agreement.