Experimental and analytical studies on the seismic response of freestanding and anchored building contents.

摘要

This dissertation presents the findings of a study undertaken to examine the seismic response of freestanding and anchored building contents, and particularly laboratory equipment such as refrigerators, freezers, and incubators. The possible modes of response are sliding and rocking, which can result in excessive displacements, impact and overturning.;The properties that affect the rocking response of equipment are presented. Results of quasi-static experiments to characterize the contact interface which affects the sliding response are then offered. Based on the experimental results, the response analysis which follows adopts two contact friction models: (a) an elastoplastic model, and (b) a rigid-plastic (Coulomb) model.;Shake table test results of freestanding equipment subjected to moderate ground and floor motions with 50% and 10% in 50 years hazard levels are presented. Although some rocking was observed, sliding was the predominant mode of response, with displacements up to 2 feet.;A physically meaningful Intensity Measure, IM, and the associated Engineering Demand Parameter, EDP, are identified. The EDP exhibits considerable scatter and is thus treated as a random variable, with mean and standard deviation obtained through regression. Subsequently, fragility curves are generated for the 50% and 10% in 50 years hazard levels, and an example that illustrates how to use them is offered.;The dynamics of a rigid block resting on a moving base are presented using a Lagrangian approach. The commercially available program Working Model is validated for pure rocking, pure sliding, slide-rocking. Results of Working Model simulations are also in good agreement with results from shake table tests on quarter-scale wooden models of the equipment subjected to time-compressed 2% in 50 years motions. The response of the full scale equipment to 2% in 50 years motions is computed with Working Model, and regression of the results leads to fragility curves for these strong motions.;Shake table test results on anchored equipment are also included. The recorded peak equipment accelerations were always larger than those of the freestanding equipment, sometimes more than seven times larger. Such high accelerations will pose a threat to laboratory equipment and the valuable material stored within it.