Local-global distribution factors method for tall building frames

Abstract

A three-dimensional finite-element analysis of tall buildings is often not possible using a personal computer due to the large number of unknowns involved. Because of the particular geometric arrangements of structural members in a tall building, the relative out-of-plane nodal displacements at a particular floor level are not sensitive to loadings at the far side. The unknowns at floor level can be reduced to three sets of independent local distribution factors. Three additional sets of global distribution factors are introduced in this paper to account for the uneven elongation (shortening) of the columns having unevenly distributed stiffnesses along the height and across the floor plane. The total number of unknowns per floor is reduced to 21. The lateral displacements are computed to within 1% in all cases studied.