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Turkish Earthquake Expert Reports on Damage


 


Earthquake Engineering Research Institute (EERI) and NEES joined efforts to send rapid response team members to Turkey to investigate building structures affected by the recent earthquake. Among the team members included Purdue University civil engineer Ayhan Irfanoglu. The team spent four and half days in Van (main city) and Ercis with teams from the Middle East Technical University, Ankara and the Dicle University, Diyarbakir.

Irafanoglu returned to the United States this week and reported that it was not possible to inspect the collapsed structures, as they were nothing more than heaps of mangled steel and concrete. There were many heavily damaged structures in Ercis and a few in Van proper. Based on their surveys, it was obvious that the heavily damaged structures suffered from fundamental structural design errors such as floor torsion, very flexible block infilled joist floors, soft ground story, captive columns, and ground story with split floor (mezzanine level) rendering some of the lateral load resisting members vulnerable.  Figures 1 and 2 are examples of the split floor construction with elevator core RC walls damaged during the earthquake (left: looking through the front/open floor; right: diagonal cracks seen on the core wall from inside)

While inspecting buildings in Van proper, the team saw many vulnerable structures that appeared undamaged from outside but showing signs of a start of critical failure modes once inspected closely. In Irfanoglu’s opinion, Van proper, which is in a seismic zone with design effective peak ground acceleration of 0.3g to 0.4g, experienced not more than 0.10g to 0.15g. As such, it would be a major mistake to suggest that the buildings in Van had passed the load test. Worse could come if the next large event strikes closer to the city.

Irfanoglu guestimates the level of shaking in Ercis suggests an effective PGA of 0.25g to 0.30g, which is no more than three quarters of the 0.4g or higher effective PGA assigned by the design seismic hazard map.