Structural systems with suspended and self-centered floor slabs for earthquake resistance
Date
2013
Authors
Chulahwat, Akshat, author
Mahmoud, Hussam, advisor
Beinkiewicz, Bogusz, committee member
Whitley, Darrell, committee member
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Abstract
The purpose of this study is to develop a novel structural system for mitigating the effects of earthquakes on building systems by suspending the concrete floor slabs of a steel building. The slab is suspended using hanger rods and act as Tune Mass Dampers (TMDs) to reduce the response of the structural system. In addition, steel links are added between the bottom face of the suspended slab and the beam below the slab and are used as energy dissipaters during an earthquake. Moreover, post-tensioned cables are installed adjacent to the steel links to provide a self-centering capability to the floor slab and eliminate residual drift after a seismic event. The Suspended Slab (SS) system is analyzed by constructing suitable theoretical models, from which mathematical equations describing the response of the system are developed and analyzed The location and number of suspended slabs and energy dissipation links needs to be carefully chosen for optimum performance of the system. To find the optimized condition, the simple optimization approach of Numerical Search is used. The optimization identifies the best locations, damping ratio and the frequency ratio of the slabs. The approach is suitable for short structures, however with increase in number of floors the algorithm becomes time costly. A new combinatorial approach of optimization is implemented that uses Nelder Mead algorithm and Covariance Matrix Adaptation Evolution Strategy. The new optimization is modified and tested to assess its effectiveness. Finally, three test structures are utilized to evaluate the effectiveness of the suspended slab system using the combinatorial optimization approach. The earthquake is modeled as a stationary white noise and Kanai Tajimi Spectrum is used as excitation input to obtain the Root Mean Square response, which is considered as the performance evaluation parameter. From the results of this study it is concluded that the suspended slab system can be quite an effective strategy for earthquake mitigation.
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Subject
CMA-ES
suspended slab
floor isolation
earthquake