Disorder and damage of base‐isolated medical facilities when subjected to near‐fault and long‐period ground motions

Abstract

SUMMARY A series of full‐scale shaking table tests were conducted at E‐Defense for a four‐story base‐isolated hospital. The operation room in the specimen was chosen for detailed examination of its disorder and damage during large ground motions. It was arranged with various medical appliances in as a realistic manner as possible, and the appliances were characterized by casters installed at the bottom to ensure mobility. Two types of ground motion, the near‐fault ground motion and long‐period ground motion, were adopted, and the responses of the appliances were recorded using the motion capture technique. Thanks to the base isolation, the floor response was greatly reduced, and no disorder or damage was observed in the operation room except for the case when subjected to a long‐period ground motion. In this case, the unlocked appliances moved seriously (by more than 3 m), and collisions occurred between the appliances and between appliances and the surrounding wall. The force of collision reached 36 kN, which is sufficient to injure a person. The acceleration due to collision was as high as 10 g, which is far beyond what can be tolerated by acceleration‐sensitive appliances. It is notable that such large motion was not observed once the appliances were locked. The test was also carried out for the corresponding fixed‐base structure. Among all cases in the experiment, by far the most serious damage occurred in the fixed‐base structure when subjected to the near‐fault ground motion, clearly because the floor response was significantly amplified from the ground motion. Copyright © 2014 John Wiley & Sons, Ltd.

Building contents sliding demands in elastically responding structures

“…Some such cases included: (i) microwaves moving several metres across rooms, (ii) heating, ventilation, and air-conditioning (HVAC) units sitting on top of roofs of multi-storey buildings being displaced, (iii) books and computers sliding off shelves and tables, and (iv) contents sliding on floors. In addition, recent experimental studies have not only reproduced the observed damage, but have also significantly improved our understanding of contents behaviour during earthquakes and enabled us to develop strategies to mitigate their impact [1][2][3][4][5][6][7][8][9][10]. Although sliding or movement of objects can result in economic loss and injury, mitigating the movement may be uneconomical.…”

“…The world-largest full-scale 3-dimentional shaking table at E-Defense laboratory in Kobe, Japan was first used to understand the seismic behaviour of non-structural components in high-rise buildings [3] and sliding behaviour of furniture and anchoring force to long-period earthquake motions [2], followed by a series of comprehensive examination of safety and functionality of based-isolated medical facilities [4][5][6]. Similarly, Yeow et al [7] conducted shaking table tests to verify current modelling techniques used in contents sliding simulation, and concluded that the static friction coefficient reasonably estimates the kinetic friction coefficient and the relationship between the force and sliding displacement can be approximated as being elastoplastic.…”

Structural and nonstructural performance of a seismically isolated building using stable unbonded fiber‐reinforced elastomeric isolators

“…The effect of different seismic isolation systems on the performance of attached equipment that behaves like viscously damped linear oscillators has been studied at various levels in [6,[14][15][16][17][18][19][20][21]. Furukawa et al [23] studied the effects of vertical motion on the structure and its contents, while Shi et al [24] focused on the seismic performance of the contents. Shake table tests of a full-scale, four-storey, base-isolated reinforced-concrete specimen representing a medical facility housing a wide variety of NCS, including furniture and medical equipment, were carried out by the Nakashima group [22][23][24].…”

Second‐mode tuned mass dampers in base‐isolated structures for reduction of floor acceleration

“…The values were obtained from design documents that presented the results of time history analyses under ground motions adopted in the Japanese design code (Japanese Ministry of Construction). To protect the various contents in the structure, the floor acceleration is generally recommended to 3 m/second 2 or less . The simulation results show that 3 types of isolation have larger accelerations than the recommended value.…”