پیشرفت و کاربردها در اتلاف انرژی لرزه ای و کنترل سازه ها در چین Recent progress and application on seismic isolation energy dissipation and control for structures in China

1 Earthquake tragedy and lessons in china A tragically strong earthquake, known as the Tangshan earthquake M7.8, happened at 3:15 on 26 July 1976. The epicenter depth was only 13 km below the surface of the earth. The fault line runs right below the city of Tangshan. The whole city was ruined, 240,000 people died, and 96% buildings collapsed, including houses, schools, hospitals, offi ce buildings and many other types of buildings (Figs. 1 and 2). Another devastating earthquake, the Wenchuan earthquake M8.0, happened at 14:28 on 12 May 2008. The epicenter depth was only 17 km below the earth’s surface. The fault also ruptured right below the city. The whole city was turned to ruins, 90,000 people died, and 80% of buildings collapsed (Fig. 3). In the same area of the Wenchuan earthquake, just fi ve years after the M8.0 earthquake, another severe earthquake, the Lushan earthquake M7.0, happened on 20 April 2013. Over 75% of buildings were damaged or collapsed in Lushan County. But after the Lushan earthquake, it was noted that one of the buildings in the Lushan County hospital had used an isolation technique. The structure had not sustained any damage, and it performed very well during and after the earthquake! There are three buildings in the Lushan County Hospital, all of which are seven story reinforced concrete structures with single level basement (Fig. 4). The one building that has an isolation system, was not damaged at the structural level nor was the interior damaged; no fi xtures fell down off of walls or ceilings and equipment inside the buildings survived. The people inside that building did not feel the shaking. This seismically isolated hospital building became the lone rescue center for the whole county after the earthquake. Thousands of injured people were treated there (Fig. 6). People in the other two hospital buildings that were designed without an isolation system experienced severe shaking, and the buildings’ structure, walls, ceilings, and equipment were all damaged (Fig. 5).