Improved wide-column-frame analogy for shear/core wall analysis

Abstract

The wide-column-frame analog is popular in design offices for the analysis of shear/core wall buildings. However, it has been found to yield erroneous results in cases where shear deformation of the walls is significant, e.g. core walls subjected to torsion. There are two sources of error. First, due to discrete modeling of the vertical joints between adjacent planar wall units, the wall elements are subjected to parasitic moments, which cause artificial flexure of the elements and eventually excessive shear deformation of the walls. Second, the rotations of the coupling beams at the beam-wall joints have been mistaken as equal to the rotations of the horizontal rigid arms and, as a result, the beam end rotations are under-estimated by amount equal to the shear strain in the walls. It is proposed that these problems be resolved by: (1) Adjusting the shear deformation factor of the wall elements to compensate for the errors in shear deformations due to artificial flexure; and (2) using beam elements with vertical rigid arms for the coupling beams, so as to eliminate the errors in beam end rotations. Substantial improvement in accuracy is achieved with these modifications.