New experimental capabilities and loading protocols for seismic fragility and qualification of nonstructural components
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The seismic vulnerability of nonstructural components and equipment with their expensive recovery and/or replacement costs has been demonstrated during past earthquakes. The limited data collected from past earthquakes and the relatively scarce research in this field are not sufficient to completely characterize the seismic behavior of nonstructural components and develop effective mitigation measures. This is a serious deficiency considering that the investment in nonstructural components and building contents is far greater compared to structural components and framing. In order to address these deficiencies and to better understand the seismic behavior of nonstructural components, the University at Buffalo Nonstructural Component Simulator (UB-NCS), composed of a two-level testing frame, has been commissioned to subject nonstructural components to realistic full-scale floor motions. The UB-NCS testing platform can subject nonstructural systems to 3g acceleration, 100 in/s velocity and ± 40 in displacement amplitudes. This new equipment provides improved experimental capabilities for more realistic qualification testing and fragility assessment of nonstructural systems. Full-scale, anchored or self-supported equipment and building contents, with attachment points at one or two consecutive building levels can be tested. Most important, equipment and combined nonstructural systems that may be sensitive to both accelerations and/or interstory drifts can be rigorously evaluated under realistic loading conditions to evaluate interdependencies among nonstructural components and the interaction with the primary structural system. The actual testing capabilities and limitations of the UB-NCS were evaluated through an extensive series of tests. The fidelity of the testing facility to reproduce, under controlled laboratory conditions, full-scale seismic floor motions expected in multistory buildings, and other random and harmonic motions was demonstrated. In order to archive a satisfactory equipment performance, an off-line compensation procedure was developed and recommended for testing of full-scale nonstructural specimens. In order to more broadly assess the seismic performance of nonstructural components, systems and equipment, independent of building or ground motion, an innovative set of testing protocols taking full advantage of the UB-NCS testing capabilities is proposed. The proposed protocols complement, and in some cases extend, the capabilities of current nonstructural qualification procedures such as the AC156 seismic qualification protocol and the fragility testing methodologies proposed in FEMA 461. In particular, new capabilities are provided for testing nonstructural systems with multiple attachment points that may be displacement and/or acceleration sensitive by simultaneously applying interstory drifts and absolute floor accelerations. The unique testing capabilities of the UB-NCS are demonstrated through a series of experiments assessing the seismic performance of a full-scale composite hospital emergency room containing typical nonstructural components such as architectural finishes, piping systems and life support medical equipment. In these tests, the seismic performance of individual nonstructural components and medical equipment was evaluated as well as the dynamic interactions and interdependencies between nonstructural systems and contents. The seismic behavior of displacement sensitive partition walls and acceleration sensitive wall mounted patient monitors were closely examined. The input motions for these tests included the loading protocol developed as part of this dissertation and simulated building floor motions.