A little over 14 years ago, At 3.34 am on February 27, 2010, a mega earthquake struck Chile, reaching a magnitude of Mw = 8.8. With a total duration of 2 minutes and 30 seconds and a depth of 30.1 km, The phenomenon affected 80% of the country.
Christened 27F, The mega cataclysm caused the death of 525 people and left 23 people missing, in addition to the subsequent tsunami that hit the national coasts.
The event was of such magnitude that it was even perceived in other countries in the region, such as Argentina and Brazil.
Now, a seismic engineering study, prepared by researchers from the University of Chile, analyzed why some residential buildings had problems resisting the earthquake, using a methodology called structural resilience assessmentor performance-based design (PBD) its designation in English.
Published by the magazine Buildingsthe investigation took as a reference case a reinforced concrete building, 16 floors and 46 meters high, located in Viña del Mar, which It suffered serious damage to all its floors after the emergency.
According to the research, based on a master’s thesis by civil engineer Betzabeth Suquillo, in which academics Fabián Rojas and Leonardo Massone and the Center for Research, Development and Innovation of Structures and Materials (IDIEM) participated, the damage this building were a consequence of the superposition of forces and the dynamics of earthquake-induced movements.
This superposition of forces and dynamics of movement It is related to gravitational actions (weights/forces on the structure that, among other things, are transformed into axial load on the walls) and the effect of the earthquake (dynamic) on the structure, which is an acceleration on the ground that translates into building vibration, and which is damaged when it moves and deforms, explains Massone.
“The novelty of this study lies in the application of performance principles defined by Chilean seismic engineering and evaluating the effectiveness of the methodology to accurately represent the behavior of a building,” says Massone.
The researcher says “that these methodologies (PBD) They allow us to better understand how a structure behaves in the event of an earthquake that can cause damage, which was validated by this study,” he adds.
Although Chile’s seismic design approach has been effective in earthquakes and has demonstrated a high level of operational performance, “in most structures, These methods have not yet been officially incorporated. as valid approaches in seismic building codes,” warns Massone.
The analysis was carried out by comparing photographic records of the breakdowns with the information provided by computer models. These allowed us to observe that, after the emergency, The building suffered accidents on different floors: cracks in the concrete, buckling of reinforcing bars at the edges of walls and detachment of the concrete layer.
The importance of evaluation protocols lies in contributing to the central objective of seismic engineering: ensuring that structures exhibit adequate behavior in the face of these natural events throughout their operational useful life. Therefore, the guidelines in most international design criteria They use immediate occupation and prevention of collapse as parameters, the document states.
In the Chilean case, the building philosophy also prioritizes human safety and structural integrity, but is distinguished by considering the characteristic configuration of buildings in the country: they are made of reinforced concrete and have a high density of walls.
The results obtained from the analyzed case demonstrated that the performance limits of structural walls align with resilience objectives considering the magnitude of the earthquake.
