Artículo de publicación ISIConcepción, near the southern end of the fault rupture zone of the offshore Maule, Chile earthquake, suffered signifi cant damage to all types of structures. Tall reinforced concrete buildings in the region were also affected, some severely. Spectacular collapse and partial collapse were experienced in two buildings, and many buildings had failure of thin shear walls that lacked suffi cient boundary element confi nement. Concrete spalling and crushing occurred and reinforcing steel buckled and were sometimes fractured

Artículo de publicación ISIThere are many modern tall buildings in Santiago that were subjected to the 27 February 2010 earthquake in Chile. Although there was not widespread damage in Santiago, there was notable damage to some tall concrete buildings that may have resulted from lack of proper detailing, the absence of 135° seismic hooks and inadequate confi nement of walls in the boundary zones. These caused buckling of the main bars and tension compression failure of the walls

SUMMARYThe goal of existing building codes and standards for the evaluation and strengthening of existing buildings is to provide for safe buildings by prescribing loads and material properties and structural analysis methods for a broad spectrum of building heights, types and construction. Experience clearly shows that building codes and standards do not provide for the most economical, efficient and safe tall buildings because the codes are general and prescriptive in nature and do not allow the structural engineer the flexibility without significant difficulty to incorporate building-specific applicable experience, education and new technologies. Tall buildings are really a special class of buildings that have unique qualities and characteristics. The design of tall buildings has been recognized by the structural engineering profession to require more care and effort in both design and construction because of the need to meet safety and performance requirements. This recognition is based in part on the large number of people at risk in tall buildings and also the negative financial impact on the community and the building owner. To meet this need, an alternative procedure for Seismic Evaluation and Strengthening of Existing

Artículo de publicación ISIAfter 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 signifi cant 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 confi nement 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 signifi cant damage was not reported in Valparasio, which is largely, situated on higher ground which steps downward to a narrow fl at area along the ocean. Similarly, signifi cant 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 defi ned at least for confi ned 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-confi ned detailing

The mega earthquake of 27 February 2010, offshore Maule, Chile with moment magnitude of 8·8 is the fi fth largest recorded earthquake in the world and, therefore, is considered to be a mega earthquake. This subduction interplate thrust earthquake occurred at the convergence of the Nazca (oceanic) plate with the South American continental plate. This type of earthquake affects the north-western region of USA and Canada, as well as Alaska. Therefore, it is important to study the characteristics of the recorded accelerograms and their effects on the future behaviour of tall buildings in USA. Although the earthquake produced accelerographic records with very high ground motions in terms of peak ground accelerations and very long duration of ground shaking, the observed damage from this earthquake was more like the level of damage expected from a moment magnitude 8⋅0 rather than a moment magnitude of 8⋅8. This may be the result of asperities in the fault rupture surface.