Desempeño de estructura metálica mediante análisis dinámico con acelerogramas ajustados con espectro medio condicional (CMS)

Abstract

The present investigation is carried out in Huachi Loreto in Ambato city, starting as a first point, to identify the geological faults near this study site that can contribute to generate a seismic event that affects the structures in the area. Using empirical formulas, the value of the shear wave velocity was obtained based on calculated values, specific to the site, such as the length of the fault, source - study distance, focal depth, expected moment magnitude, and values of the number of blows of the SPT test performed in situ. This shear wave velocity allows determining the type of soil existing in the area according to the ranges established by the Ecuadorian Construction Standard (NEC 2015). Subsequently, an attenuation model was chosen (Montalva) that allows to determine, by applying certain equations called GMPEs (ground motion prediction equations), a possible behavior of the soil based on complementary data to those already mentioned specific to the site such as distance and hypocentral depth. From the GMPE graph and the uniform hazard spectrum (UHS) and applying certain equations determined in the Bakker model, the conditional mean spectrum (CMS) was obtained. The use of this spectrum allowed a comparison of the behavior of a metallic structure proposed in this study, with respect to the elastic spectrum imposed by the NEC. This comparison was made on the basis of the results provided by the nonlinear dynamic analysis (time-history), through which the performance of the same structure subjected to scaled seismic events was determined with respect to the CMS and the NEC spectrum. It was obtained as a result that the seismic demand produced by the NEC spectrum is greater than that produced by the CMS, since the pseudospectral accelerations have a great difference between these spectra, which is why the maximum displacements and drifts are reduced by approximately 65 percent by applying the CMS in the present investigation.