CEEM Graduate Student/Post-Doc Seminar Series - April 7
Title:
Seismic analysis and optimal design of irregular multiple rocking buildings
Abstract:
Traditionally, lateral load-resisting systems are designed to dissipate seismic energy by developing plastic mechanisms in the primary structural elements. Lessons from recent seismic events have shown that the resilience of the building is an important factor that should be considered at the design stage. Therefore, self-centering damage-free systems have been developed. These systems are designed to dissipate seismic energy using replaceable special devices. In addition, post-tensioned cables are designed to eliminate the residual deformations providing a self-centering behavior. Experimental and numerical studies have shown that these systems could withstand large earthquakes with minor damage and negligible residual deformations allowing for fast recovery after seismic events.
Although these systems have shown promising behavior, their design is not straightforward due to their complex dynamic behavior. The available design methods are simplified and often lead to violation of the predefined performance targets when examined by accurate analysis. In addition, these methods are limited to simple regular buildings. In practice, the architecture of the building often dictates the design of an irregular structural system. In this study, a general method was developed for the seismic design of multiple-rocking self-centering concentrically braced frames (SC-CBFs). The proposed method relies on the gradient-based optimization approach.
The optimization problem is formulated to minimize the construction cost. The performance constraints are formulated following current seismic design codes and the performance-based seismic design methodology. These constraints are computed using an efficient numerical integration scheme for the nonlinear time history analysis of SC-CBFs developed in this study. This ensures that the performance targets are not violated.
The results show that these systems were efficiently designed using the proposed method with a reasonable computational cost. In addition, it is shown that the multiple rocking solution, originally proposed to mitigate the higher vibration modes effect, is effective for the cost reduction of complex irregular buildings.
Speaker Bio:
Dr. Ameer Marzok is a postdoctoral researcher in the Department of Civil Engineering and Engineering Mechanics within the group of Prof. Haim Waisman. His research interests lie in topology optimization, seismic design, thin-walled structures, nonlinear finite elements, the extended finite element method (XFEM), and nonlinear dynamics. Before joining Columbia, he received his Ph.D. at the Technion - Israel institute of technology, advised by Prof. Oren Lavan.
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