Analysis of Shear Cores Using Superelements

Abstract

A number of multistory buildings, containing concrete shear cores to house vertical services, have sustained major damage in recent earthquakes. Simplified analytical models for the shear cores cannot account for the relative stiffness of intersecting walls and for the influence of openings on the wall stiffness. Wall stress calculations are also beyond the capabilities of many of these continuum models. To remedy this, a three-dimensional shear core analytical model composed of two-dimensional rectangular plane stress and plate bending finite elements was developed. A subassemblage of finite elements forms a superelement and a stack of superelements is assembled in series elimination fashion to model the core tower. Determination of vibration frequencies, mode shapes, and nodal displacements for several isolated shear cores demonstrates the capabilities of the model. This general purpose analytical model can be readily incorporated into existing multistory-building frame models, and can serve as a basis for evaluation of simpler continuum models.