Estimating seismic base shears of tall wall-frame buildings

An approximate method for determining the seismic base shear of high-rise building structures on the basis of the preliminary design information is presented. The method is based on the generalized representation of the family of shear-flexure cantilevers by the coupled-wall theory, and is applicable to nontwisting structures consisting of any combination of walls and frames that are uniform with height. Such structures include coupled shear walls, walls connected by beams to columns, and wall-frame structures. The static and dynamic behavior as well as the geometric and material properties of shear-flexure cantilevers are fully described in terms of two nondimensional characteristic parameters. A decoupled eigenvalue approach is used to evaluate the base shear coefficients corresponding to the first two periods of free vibration. The derivation of the method as well as a comparison of its results with those obtained by earlier approximate methods and by a discrete finite element dynamic analysis are given. A worked example is given to illustrate the application of the method.