دانلود رایگان مقاله انگلیسی شناسایی پاسخ لرزه ای غیر خطی ساختمان ها توسط حمل و نقل استوک ول - اشپرینگر 2017

Abstract

In presence of soil–structure interaction (SSI), changes in dynamic properties of the system can be related to nonlinearities in both the structural and soil response. Identifying the nonlinearities related to non-stationary phenomena due to structural damage is an important issue for damage detection and localization. In this study, a novel approach is proposed to identify the non-linear structural response of an instrumented building in presence of SSI. Considering the advantages provided by the use of the time–frequency representation to explore the time-variant behavior of the system, and the direct evaluation of the shear wave velocity by the use of the deconvolution interferometry to decouple structural response from soil response, a combined Stockwell Transform and deconvolution interferometry approach is presented. The combined approach is applied to a selected data set of a well-documented building, the Jalapa building, whose nonlinear response was already investigated with other methods. This offers the possibility to validate the results obtained by the proposed approach. Jalapa building is a reinforced concrete structure, located on soft clay in Mexico City. Both SSI effects and structural and nonstructural damage affected the building response during earthquakes in the 1990s. The building was retrofitted twice during its lifetime. The data of three events are considered when investigating the changes in dynamic properties of the structure due to damage and retrofitting. The results allow us to detect the different phases of non-linear structural response in a reasonable agreement with the documented status of the building after each event.

5 Discussion and conclusion

In this paper, a novel approach is presented to detect the nonlinear dynamic response of damaged structures influenced by soil–structure effects by processing earthquake records and computing the variations of the fixed basefrequencies of the building during a seismic event. In order to monitor the status of a structure during and after earthquakes in presence of soil–structure interaction, it is necessary to decouple the building response from soil– foundation coupling. To this regard, a combined approach of the S Transform and deconvolution interferometry is proposed. It derives from the advantage of the use of the time–frequency representation by application of S Transform to identify the time-variant behavior of the system. Since the variation of the fundamental frequency maybe also related to the nonlinear response at the soil foundation interface, we proposed to apply the deconvolution interferometry to the local spectra of the S Transform because it separates the properties of the building itself from the soil-foundation contributions. Moreover, the limitation to time-invariant system when applying the deconvolution interferometry is overcome in our approach by considering stationarity of the signals in each frequency dependent Gaussian window of S Transform. The main advantage of the proposed method is that provides an estimate of time- variations of the dynamic parameters (such as shear wave velocity and hence the corresponding fixed-base frequency), related only to the occurrence of non-linear response of the structure under a strong earthquake.