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1、北京交通大学毕业设计（论文）外文翻译Influence of isolator characteristics on the responseof base-isolated structureVasant A. Matsaar 1Z.S. JanidsAbstractThe influence of isolator characteristics on the seismic response of multi-story base-isolated structure is investigated. The isolated building is modeled as a shear
2、 type structure with lateral degree-of-freedom at each floor. The isolators are modeled by using two different mathematical models depicted by bi-linear hysteretic and equivalent linear elastic-viscous behaviors. The coupled differential equations of motion for the isolated system are derived and so
3、lved in the incremental form using Newmarks step-by-step method of integration. The variation of top floor absolute acceleration and hearing displacement for various bi-linear systems under different earthquakes is computed to study the effects of the shape of the isolator hysteresis loop. The influ
4、ence of the shape of isolator force-deformation loop on the response of isolated structure is studied under the variation of important system parameters such as isolator yield displacement, superstructure flexibility, isolation time period and number of story of the base-isolated structure. It is ob
5、served that the code specified equivalent linear elastic viscous damping model of a bi-linear hysteretic system overestimates the design bearing displacement and underestimates the superstructure acceleration. The response of base-isolated structure is significantly influenced by the shape of hyster
6、esis loop of isolator. The low value of yield displace-ment of isolator (i.e. sliding type isolation systems) tends to increase the superstructure accelerations associated with high frequencies. Further, the superstructure acceleration also increases with the increase of the superstructure flexibili
7、ty.keywords: Base isolation; Earthquake; Elastomtric bearing Sliding system; Bearing displacement; Superstructure acceleration; Bi-linear hysteresis;Equivalent linear.1 IntroductionSeismic isolation, which is now recognized as a mature and efficient technology, can be adopted to improve the seismic
8、performance of strategically important buildings such as schools, hospitals, industrial structures etc., in addition to the places where sensitive equipments are intended to protect from hazardous effects during earthquake 1-3. Based on the extent of control to be achieved over the seismic response,
9、 the choice of the isolation system varies and thereupon its design is done to suit the requirements of use of the structure. In seismically base-isolated systems, the superstructure is decoupled from the earthquake ground motion by introducing a flexible interface between the foundation and the bas
10、e of structure. Thereby, the isolation system shifts the fundamental time period of the structure to a large value and/or dissipates the energy in damping, limiting the amount of force that can be transferred to the super structure such that inter-story drift and floor accelerations are reduced dras
11、tically. The matching of fundamental frequencies of base-isolated structures and the predominant frequency contents of earthquakes is also consequently avoided, leading to a flexible structural system more suitable from earthquake resistance viewpoint. The two most common types of base isolation sys
12、tems adopted in practice utilize either rubber bearings or sliding systems between the foundation and superstructure for the purpose of isolation from ground motions in the buildings as well as bridges. It is very essential to understand the different parameters affecting the response of base-isolat
13、ed structure when used for seismic protection of the structures. Especially in case of the base-isolated structures, that houses sensitive equipments, determination of acceleration imparted and associated peak displacement are the key issues for the design engineer 4. Moreover, the pounding and stru
14、ctural impacts in case of baseisolated structures made upon the adjacent structures, when separation gap distances are inadequate, become a major concern because these phenomena may lead tocatastrophic failures leading to immense isolator damage. Such failures and damages can be avoided by properly
15、estimating the peak isolator displacement and recommendation of appropriate isolation gap distances. In order to predict peak displacement and determine accurate separation gap distance requirement for a base-isolated structure, it is mandatory to know, in prior, the different parameters that affect
16、 the bearing displacement and its consequent effect on thesuperstructure acceleration. The failures due to such impacts can be avoided by reducing the peak bearing displacement by compromising with increase in superstructure acceleration to an acceptable level i.e. tolerable reduction in effectiveness of isolation. Selection of different parameters characterizing an isolation system is important in view of keeping a control over response quantities especia
