Identification of the nonlinear seismic response of buildings by a combined Stockwell Transform and deconvolution interferometry approach

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.