Three-dimensional nonlinear dynamic analysis of multi-base seismically isolated structures with uplift potential
The complexity of modern seismically isolated structures requires tools for fast, accurate and reliable analysis and the ability to capture potential discontinuous phenomena such as isolator uplift and their effects on the superstructures and the isolation hardware. In this paper an analytical model is developed and a computational algorithm is formulated to analyze complex seismically-isolated superstructures even when undergoing highly-nonlinear phenomena such as uplift. The computational model developed has the capability of modeling various types of isolation devices with strong nonlinearities, analyzing multiple superstructures on multiple bases, and capturing the effects of lateral loads on bearing axial forces, including bearing uplift. The model developed herein has been utilized to form the software platform 3D-BASIS-ME-MB, which provides to the practicing engineering community a versatile tool for analysis and design of complex structures with modern isolation systems. For purposes of verification, two numerical examples have been analyzed using 3D-BASIS-ME-MB and key results are compared to experimental results, or results obtained from other structural/finite element programs. In both examples, the analyzed structure is excited under conditions of bearing uplift, thus yielding a case of much interest in verifying the capabilities of the developed analysis too.