Influence of soil-structure interaction on the fragility curves of medium-height moment resisting frames and thin-walled buildings located in Bogotá, Colombia

Abstract

Nowadays, Bogotá’s population accounts for 15% of the total Colombian population. The population influx the city has experienced has increased the construction of buildings in the past decades. Mid-rise buildings represent over 24% from the total building stock of the city and have been constructed mainly using reinforced concrete (RC) structural systems such as moment resisting frames and thin walls. The vulnerability of such systems has been studied and documented through fragility curves that are constructed based on structural analysis results and laboratory tests. The common practice among practicing engineers to carry on the structural analysis is assuming a fixed base building, which means that the structure is founded on rock or soils with a considerable strength, neglecting the displacements that can be produced due to the presence of the foundation and the soil beneath. Such assumption may lead to inaccurate results in the case of Bogotá where an important percentage of the foundation subgrade are soft clays with high compressibility and low bearing capacity. This type of soils has been proved to affect considerably the seismic performance of buildings during earthquakes. Therefore, this research studied the influence of the soil-structure interaction on structural analysis of RC moment resisting frames and thin walls mid-rise buildings founded on the soft soils area of Bogotá by means of dynamic analysis using OpenSees. Results showed that considering both the foundation and the soil, the stiffness and the system ductility reduce, and the fragility compared to the common fixed base approach increases