Statistical analysis and ground motion effects on corner buildings with infill walls collapsed during the September 19, 2017 earthquake in Mexico

Abstract

The September 19, 2017 earthquake (Mw = 7.1) struck México between the states of Puebla and Morelos. The ground motion damaged buildings near the epicenter and in Mexico City, with 44 collapsed buildings and many more experiencing some level of damage. The study gathers and statistically analyzes all available information, identifying characteristics in the plan and elevation of the damaged structures. The analysis identified structural issues typically associated with damage, such as buildings with soft or flexible ground floors and corner buildings supported by reinforced concrete frames. Corner buildings often have infill walls on two sides adjacent to neighboring properties, which, when connected to columns, cause significant torsional effects. The corner effect, combined with other structural pathologies such as soft-story, irregular building shapes, and seismic amplification effects in some city regions, significantly contributed to the damage and building collapses presented during the earthquake. The results, in addition to showing damage statistics for buildings located in a corner with infill walls, showed that the facade walls in the corner provide very little lateral stiffness comparatively to the stiffness of the perimeter walls situated on the other two sides of the building, which causes significant torsion in the building. The study also revealed that corner buildings with infill walls next to low-rise buildings were significantly more at risk than those surrounded by buildings of similar heights. A non-linear analysis of a case study showed that the observed earthquake damages in corner buildings were indeed expected, given the building’s seismic demands obtained with the numerical model.