Nonlinear response history analysis has generally been utilized in seismic design practice to analyze structures with unusual geometry that possess significant post-elastic ductility. Nonlinear analysis has also been used within a performance-based design framework to demonstrate adequate seismic performance and address non-conformance with prescriptive building code provisions. This paper presents a case study on the inelastic seismic response of a tall, round concrete tower that exceeds code-prescribed height limitations for a concrete shear wall system. Features of the tower include an offset observation cab, with a unique cantilevered system and vertical post tensioning to provide self-centering during major earthquake events. Material nonlinearity, post tensioning effects and foundation elements were modeled explicitly. A suite of hazard-specific ground motions were selected and scaled to account for numerous factors, including soil nonlinearity. The seismic response of the tower was evaluated, with special attention devoted to the selection of appropriate performance goals and acceptance criteria.
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