Performance of tall buildings in Viña del Mar in the 27 February 2010 offshore Maule, Chile earthquake

Abstract After the devastating offshore Maule, Chile earthquake of moment magnitude 8.8 on 27 February 2010, the Los Angeles Tall Buildings Structural Design Council (LATBSDC) organized a reconnaissance team to visit the Santiago, Concepción and Viña del Mar areas. This report summarizes the highlights of the damage observed in the Viña del Mar area on the coast 120 km west‐north‐west of Santiago and much closer to the subduction rupture zone than Santiago. A significant portion of Viña del Mar is uniquely situated on variable ground conditions, particularly in the area with most of the damaged buildings. The Viña del Mar area also included tall buildings constructed before and damaged by the large 3 March 1985 magnitude 7.8 Offshore Valparaiso earthquake, which were damaged again in the 2010 earthquake. The predominant observation in these buildings was the lack of confinement and ductile detailing of shear walls. The second observation was the high demand in the localized Viña del Mar area. The apparently high demand on buildings clustered in the Viña del Mar area may be an observation based on the damage since most of the taller structures in the area are somewhat clustered in Viña. But significant damage was not reported in Valparasio, which is largely, situated on higher ground which steps downward to a narrow flat area along the ocean. Similarly, significant damage was not reported in new buildings along the coast just North of Viña del Mar. The authors' conclusion based on these observations is that the ground conditions in Viña del Mar relate to the level of demand and the level of demand is higher. Demand is variable geoseismically but with the local history of many earthquakes from the same source zone, the characterization should be regularized. However, structural response is much better defined at least for confined elements with tested and predictable analytical characterization. Regardless, the detailing of reinforcing in reinforced concrete must relate to the expected demand and duration. In addition, the structural system and elements need to be designed and detailed to prepare a building to survive a higher unanticipated demand without collapse. However, despite the apparently large demands due to the large magnitude earthquake with strong aftershocks and the long duration of seismic motions, building collapses did not occur even with limited capability due to non‐ductile and non‐confined detailing. Copyright © 2010 John Wiley & Sons, Ltd.