Estimación analítica del coeficiente básico de capacidad de disipación de energía (R0) para edificios de concreto reforzado con sistema de resistencia sísmica de muros de carga delgados

Abstract

The structural system of thin bearing walls (industrialized) has gained importance since the 1980s and with greater force since 2012 in the national territory for the construction of housing, especially social housing in almost all socioeconomic strata, becoming the most widely used system in recent years. The requirements and design assumptions contained in the NSR-10 code were evaluated in this document to verify their compliance. In this study, the basic response modification coefficient was estimated for a case study composed of twelve buildings with a lateral load resisting system of thin bearing walls featuring 6, 12 and 20 stories, located in areas of intermediate and high seismic hazard with two local soil conditions, namely, type C and type D. The basic response modification coefficient was estimated with two analytical alternatives widely implemented in the technical literature: the proposal of Uang (1991) and the proposal of Whittaker, Hart & Rojahn (1999), using the response of the structure at the design earthquake, estimated via non-linear static analysis following the widely known Capacity Spectrum Method (CSM) as outlined in FEMA-440. For the first alternative, the estimated basic response modification coefficient varied between 42% and 62% of the value recommended in the code, while, for the second alternative, considered more consistent with the code provisions, the estimated basic response modification coefficient ranged from 95% to 115% of the recommended value. The results indicate that, for the buildings in the study case, the basic response modification coefficient indicated in the code is adequate, if shear resistance is guaranteed, and to ensure such behaviour, the over-strength factor could be modified by adopting a formulation based on the period of vibration of the predominant mode in each main direction. In the same way, seismic shear force demands in walls obtained from the elastic analysis could be amplified by the over-strength factor and, additionally, by a factor that considers higher mode effects.