An improved Chinese load code method for the evaluation of wind‐induced base shear force on base‐isolated buildings

Abstract

The isolator units in a seismically isolated structure shall have a surplus yield strength under wind loads. The isolation interface must have enough strength to state at an elastic stage under wind loads. This necessitates an accurate evaluation of wind‐induced base shear force. Initially, to calculate the equivalent static wind load (ESWL) and the base shear force of a base‐isolated building, the validity of the inertial wind load (IWL) method and Chinese load code (CLC) method, the simplification based on the IWL method, are examined via comparison with response‐history analysis results. Comparative analysis reveals that the IWL method was more accurate in evaluating the ESWL and the base shear force of base‐isolated building, while the CLC method underestimated them due to the following reasons: inaccurate fundamental modal shape, a reduced peak factor, the omission of the ESWL contribution from the isolation interface, and flawed assumptions of uniform mass distribution. Subsequently, an improved CLC method that combined the exponential modal shape and first modal generalized mass modification coefficient is proposed and verified by a case study. Compared with the CLC method, the fluctuating base shear force calculated by the improved CLC method increased by 10% in the case study. Finally, the effect of non‐uniformly distributed mass is further considered in the proposed method by devising a mass conversion coefficient, and the case study has also validated this method. Without considering the effect of the non‐uniform mass, the fluctuating base shear force will be underestimated by 7.8% in the case study.