Pullback Test for Seismic Performance Evaluation of Safe Rooms

Pullback test has no scrupulous theoretical establishment. It is based on the hypothesis that the response ofthe structure can be related to the response of an equivalent single degree-of-freedom (SDOF) system. This implies thatthe response is controlled by a single mode. In fact, the steel frame of each safe room, which is introduced within theunreinforced masonry buildings for protecting the lives of residents in catastrophic earthquake failures, contains aSDOF structural system. In pullback test, the steel frame carries its gravity load first, and then it will be pushed underan incremental lateral roof displacement pattern, which is imposed to its center of mass. This paper expresses theresults of 13 pullback tests executed by the authors on the steel frames of safe rooms. The results show that pullbacktest is a practical method for seismic performance evaluation of safe rooms. Also the performance of these frameslocated in a collapsing three storey masonry building is presented with favorable conclusions. In fact, the results ofpullback test of the safe room located at the ground-floor level were compared with the requirements of Iranian codefor seismic resistant design and it was concluded that the steel frame had an acceptable performance against seismiceffects.