91-0005 3D-BASIS - Nonlinear Dynamic Analysis of Three-Dimensional Base Isolated Structures: Part II S.Nagarajaiah, A.M.Reinhorn, M.C.Constantinou 1991 University at Buffalo 152 PB91-190553 0 This report deals with the development of a comprehensive analytical model and solution algorithm for nonlinear dynamic analysis of three-dimensional base isolated structures and the development of computer program 3D-BASIS. A new analytical model and solution algorithm involving the pseudo-force method is developed. New biaxial and uniaxial models of isolation elements are developed. The novelty of the analytical model and solution algorithm is its capability to capture the highly nonlinear frictional behavior of sliding isolation systems in plane motion. Nonlinear behavior is restricted to the base and the superstructure is considered to be elastic at all times. The nonlinear isolation system may consist of elastomeric and/or sliding bearings, linear springs and viscous elements. The solution algorithm consists of the pseudo-force method with iteration. Comparison of the computed results with experimental results is presented for verification. A six story reinforced concrete base isolated structure is analyzed to demonstrate the efficiency of the algorithm. Base Isolated Structures, Three Dimensional Structures, Base Isolation Devices, Pseudo Load Formulation, Nonlinear Dynamic Analysis, Computer Programs, Dynamic Analysis, Nonlinear Behavior, Mathematical Models, Hysteretic Models, Analytical Models, Multistory Buildings, 3D-BASIS, Secondary Systems, and Protective Systems.