3D-BASIS-TABS: Computer Program for Nonlinear dynamic Analysis of Three Dimensional Base Isolated Structures

Keywords: 3D-BASIS-TABS, Computer Programs, Nonlinear Dynamic Analysis, 3D-BASIS, Base Isolated Structures, ETABS, Three Dimensional Analysis, and Superstructure Member Forces.

Abstract: The new computer program 3D-BASIS-TABS, an extension of 3D-BASIS and ETABS, is a special purpose program developed for nonlinear dynamic analysis of three dimensional base isolated structures. The program can analyze base isolated structures with an elastic superstructure and inelastic/nonlinear isolation system. 3D-BASIS-TABS has three options for modeling the elastic superstructure: 1) three-dimensional shear building representation; 2) full three-dimensional representation; and 3) three-dimensional building representation via a stiffness matrix supplied by the user. This report describes the development and verification of the new program, which includes linear beam, column, shear wall and bracing elements to model the elastic three-dimensional superstructure and inelastic/nonlinear elements to model the isolation system. The superstructure member forces are computed in 3D-BASIS-TABS by back substitution, after the nonlinear time history analysis is completed and peak member forces are output to facilitate the design of members. The verification of the program 3D-BASIS-TABS is presented in two case studies, three-story and eight-story buildings with various isolators. These case studies serve also as examples of use of this computer program. A comprehensive user's manual with input/output files is presented.