Experimental Research For Safety Assessment Of Reinforced Concrete Frame Structures After Earthquake

It is very important to give an accurate safety assessment for damaged buildings quickly after an earthquake. The assessment results can help people to find out hazardous buildings and to avoid more casualties. It can also tell people which buildings are safe and can be used. Then public sentiment can be stabilized and social order in the earthquake region can be restored as soon as possible. At present, the safety assessment of buildings after earthquakes mainly depends on experience and visual judgment of the experts. Such an approach is difficult to avoid the deviation of the assessment results due to the different understanding from various experts. In order to solve this problem, our research group developed a new method for earthquake safety assessment of buildings which has more objective index and then is more practical. This method established the correspondence between damage phenomenon and damage index of typical RC components through large number of experiments. Then an atlas was provided based on the damage photos of such components and this atlas can be used to evaluate the damage state of RC components by damage index. After that, the damage index and damage state of the whole building can be obtained by simply weighted adding the damage index of each component.As a part of such works, the main contents in this study are as follows:(1) According to a real structure, four RC beams and four RC frames with various filler walls were tested under reversed cyclic loading. The force-displacement hysteretic curves and skeleton curves were obtained through the tests. Also, the ductility, energy dissipation capacity and stiffness degradation of the specimens were obtained.(2) Several cameras were used during the tests to take photos recording the damage state of each specimen (with and without cement mortar) at each characteristic displacement level. The modified Park-Ang damage index was selected to evaluating the damage state of the specimens. By studying the relationship between damage phenomenon and damage index, the relationship among damage level, damage photos and the corresponding damage index was established. The result can be taken as reference for seismic damage assessment.(3) The teaching building of the Longquan Middle School (a four-story RC frame structure and damaged during the Ludian earthquake in 2014) was choosen as a studying case. The damage phenomenon of each component and the whole building were reproduced by the software of SketchUp. Then the damage level of the structure was evaluated by using the method proposed in this study. Finally, the evaluating result of our method was compared with the assessment result given by the experts shortly after the earthquake.