Experimental and analytical studies on the response of freestanding laboratory equipment to earthquake shaking

Abstract

SUMMARYThis paper presents results of a comprehensive experimental program on the seismic response of fullscale freestanding laboratory equipment. First, quasi-static experiments are conducted to examine the mechanical behavior of the contact interface between the laboratory equipment and floors. Based on the experimental results, the response analysis that follows adopts two idealized contact friction models: the elastoplastic model and the classical Coulomb friction model. Subsequently, the paper presents shake table test results of full-scale freestanding equipment subjected to ground and floor motions of hazard levels with corresponding displacements that can be accommodated by the shake table at the UC Berkeley Earthquake Engineering Research Center. For the equipment tested, although some rocking is observed, sliding is the predominant mode of response, with sliding displacements reaching up to 60 cm. Numerical simulations with the proposed models are performed. Finally, the paper identifies a physically motivated intensity measure and the associated engineering demand parameter with the help of dimensional analysis and presents ready-to-use fragility curves.

Experimental and analytical studies on the response of 1/4-scale models of freestanding laboratory equipment subjected to strong earthquake shaking

“…The shake table experiments presented in Konstantinidis and Makris (2009) indicated that the primary mode of response is sliding. However, rocking and possible overturning may happen for interfaces with larger coefficients of friction, μ, and for equipment with more slender configurations (smaller α).…”

“…In practice, excessive sliding is prevented by restraining the equipment. Although this may succeed in reducing sliding displacements, it substantially amplifies accelerations (Konstantinidis and Makris 2005b). The problem of equipment sliding has been studied in the past at various scales by Shao and Tung (1999), Lopez Garcia and Soong (2003a,b), and Hutchinson and Chaudhuri (2006).…”

“…In an earlier paper (Konstantinidis and Makris 2009), the authors presented experimental and analytical studies on the seismic vulnerability of freestanding laboratory equipment located on various floor levels of a research laboratory building located at the University of California, Berkeley, campus-herein referred to as the UC Science Building. The equipment of interest included low-temperature refrigerators, freezers, incubators, and other heavy equipment.…”

“…The results of the shake table tests to moderate (POE of 50% in 50 years and 10% in 50 years) hazard motions were used by Konstantinidis and Makris (2009) to validate the commercially available dynamic simulation software Working Model 2D (2000). However, experimental validation of Working Model for full-scale equipment to motions with large hazard level (POE of 2% in 50 years) could not be performed because the ground and floor displacements which resulted from these motions could not be accomodated by the shake table at the UC Berkeley PEER Center, which has a horizontal displacement capacity of ±15 cm.…”

Dynamic Response of a Rigid Slab Supported by Four Rigid Cylinrical Rocking and Wobbling Columns

“…Indeed, a simple freestanding rocking block has been systematically studied for more than five decades both when the block is assumed rigid [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and when it assumed deformable [27][28][29][30][31][32][33][34][35][36][37]. Small scale experiments have been also performed [38][39][40][41][42][43][44][45][46][47][48][49][50][51]. It has been proven that structures that rock inplane (2d rocking) have remarkable dynamic stability.…”