New Method Of Safety Assessment Of RC Frame Structure Post Earthquake Based On Damage Index

By accurate safety assessment of buildings after earthquakes, the efficiency of disaster relief during the period of earthquake emergency can be improved. Also, the assessment results are useful for restoration and reinforcement of the damaged buildings. Now, the safety assessment of buildings after earthquakes mainly depends on experience and visual judgment of the experts. That means the persons performing the safety assessment should be familiar with the knowledge of structural engineering and also should have rich experience on structural safety assessment. Although we already have a national code on structural safety assessment( "Post-earthquake field works-Part 2: Safety assessment of buildings"(GB 18208.2-2001)) which is based on valuable experience of many researchers, but the methods provided in this provision still rely on the observation and 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) Experiments of typical reinforced concrete beams, columns and single span reinforced concrete frames(with and without infill walls) were conducted by other students in our research team. The mechanical properties of these specimens were simulated by the software of OpenSees in this study. The results from the numerical simulations were compared with that from experiments, and then the key parameters of the finite element models were determined.(2) The teaching building of the Longquan Middle School(a four-story RC frame structure and was damaged during the Ludian earthquake in 2014) was choosen as a study case. Finite element model of this building was established. The earthquake records very closed to this building(nearly 150m) were monitered and were used as the earthquake input for the numerical model. Seismic responses and damage indices of each component in the building were calculated. Also, the method calculating the damage index of the whole building by using the indices of each component were addressed.(3) In many cases, damage situation of only part components in one building can be surveyed. In these cases, the appropriate method calculating the damage index of the building was addressed.