Even though damaged equipment represents a major cost in earthquake disasters, a validated seismic procedure for designing protective systems for equipment does not exist yet. The objective of this project is to define seismic protective mechanisms based on wire rope isolators (WRIs) for three different equipment mounted in a six-story hospital building. The equipment includes an electrical generator on the ground floor, a computer server on the 4th floor, and a cooling tower at the roof. The study includes: (1) the definition of seismic demands on equipment mounted in low-rise buildings; (2) identification of WRI mechanical properties in different configurations; (3) designing of WRI systems to support the equipment on the scope of this work, and (4) the evaluation of the designs using numerical analysis. On the seismic demand’s definition, an available methodology is adjusted and implemented to generate the spectral absolute floor accelerations; further, the seismic demands obtained from two code-specifications (ASCE7-16, and AC156-ICC) are used for comparison purposes. The dynamic characteristics of the systems are selected to avoid resonance by defining an isolation period away from the natural frequencies of the building. The protective systems are defined to be relatively stiff with an energy-dissipation capacity to mitigate seismic effects. The WRI systems are designed in two configurations: (1) a conventional WRI platform with WRIs working in shear/roll in the horizontal direction, and tension/compression in the vertical direction, and (2) a platform with inclined WRIs. The platforms with inclined WRIs are implemented to mitigate the seismic rocking responses of the conventional configuration by reducing or eliminating the eccentricity between the system center of stiffness and equipment center of mass. Numerical analyses are conducted using nonlinear time history analysis to evaluate the design of equipment-platform sets subjected to six recorded motions in all directions. When the inclined WRIs are implemented, the results of the study shows that: (1) the rocking responses on platform subjected to different recorded motions are significantly reduced with a range of 74% to 95% for the cooling tower, 99% to 100% for the computer server, and 98% to 100% for the electrical generator, 2) significant reduction in equipment deformations are noticed about 50% to 90% for the cooling tower, 7% to 51% for the computer server, and 29% to 94% for the electrical generator. Results from the numerical analysis suggest that further investigations are necessary to study the effects of the modeling assumption using SAP2000 on the analysis of WRI platforms.
|Commitee:||Arhin, Stephen A, Marin-Artieda, Claudia, Yazdani, Hessam|
|School Location:||United States -- District of Columbia|
|Source:||MAI 81/9(E), Masters Abstracts International|
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