Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform's movement should reproduce real ground acceleration records. However, the stroke of the platform, required for reproduction of real records, is usually rather large. This limitation does not allow an accurate realization of the ground motion by the shaking table. Commonly, in order to overcome this problem, original records are modifi ed, which causes a signifi cant change in the acceleration records' spectra. That is why structural responses to the original and to the modifi ed records are different. A new method for modifi cation of original acceleration records is proposed, in which the original record is corrected by an additional artifi cial one that changes the shaking platform's displacement. The corrected record is obtained as a sequence of impulses. The magnitude and duration of each impulse, as well as their location on the time scale, are obtained by an optimization procedure. The optimization is implemented according to a performance index, aimed to minimize the infl uence of the correcting acceleration record on the spectrum of the original one. The proposed method has higher reproduction accuracy, compared to other known methods. Its effectiveness is demonstrated by comparison of response spectra and dynamic behaviors of three multi-story structures subjected to natural and modifi ed seismic excitations.
Modern international standards to end products include a complex of requirements to parameters, materials, performance, and methods of control and acceptance. Development and implementation of standards in practice requires studying of them by a wide range of experts in areas of development of these products, manufacturing techniques, control and acceptance, as well as in areas of their final application. The new standard EH15129 "Antiseismic devices" includes requirements to elastomeric isolators which are widely applied in seismic protection systems of bridges and other civil structures. Requirements to isolators are provided as results of tests in regimes closest to operational. In this paper we propose a method for studying the requirements of the standard by virtual testing of seismic isolators virtual models. At these virtual tests the time-varying actions are reproduced according to the standards requirements (constant, ramp, triangular, and sinusoidal). Virtual models of isolators allow to realize their main properties that affect the test results, such as non-linear elasticity, scragging, damping, creep, and elastic-plastic behavior. For realization of the method, a Simulink environment of MatLab is adopted, allowing to reproduce virtual testing in the form closest to the real tests. The set of virtual models for tests has been created and presented in the form of virtual laboratory which includes library of models of isolators, library of loadings and library of measuring tools. An example of virtual standard tests of commercially available seismic elastomeric isolator is presented in the paper. ß 2015 Wiley Periodicals, Inc. Comput Appl Eng Educ 23:556-566, 2015; View this article online at wileyonlinelibrary.com/journal/cae;
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