Seismic performance of mid-rise thin concrete wall buildings lightly reinforced with deformed bars or welded wire mesh

Abstract

The increasing demand of housing in urban areas in Latin America has driven the construction of a significant number of buildings using reinforced concrete (RC) walls with thickness equal or lower than 100 mm, with a single layer of reinforcement provided by a welded-wire mesh (WWM) or by deformed bars (DB). Several concerns related to the lack of ductility, scarce evidence on its behavior during earthquakes, and the lack of clarity of design guidelines in earthquake-resistant codes for this structural system have risen in recent years. This research aims at providing evidence on the seismic risk of thin concrete wall buildings reinforced with two types of reinforcement. A six-story building, constructed in Bogot´a, Colombia with walls having 100 mm thickness and detailed with WWM is used as case study. After gathering relevant information from the building structural drawings, a nonlinear model was created in OpenSees using the shear-flexure interaction multiple vertical line element (SFI-MVLEM). To evaluate the effect of steel ductility, a second benchmark model of the studied building was created using deformed bars (DB) as reinforcement. Incremental dynamic analyses were conducted on the models using the far field ground motion suite provided by the FEMA P-695 and a set ground motions for subduction zones, which served as input for the development of fragility functions for the building. The results show that the fracture of reinforcing steel is a frequent failure mode of the building reinforced with WWM, whereas the failure of the building reinforced with DB was controlled by the drift limit of the walls. The findings also show that probabilities of failure for the ground motions scaled to the maximum credible earthquake are 41% and 25% for the building reinforced with WWM and DB, respectively. These large probabilities suggest that the use of thin RC walls for mid-rise buildings should be limited in seismic prone areas, especially those detailed with WWM.