SEISMIC FRAGILITY ANALYSIS OF STEEL FRAMES WITH FULLY-BOLTED CORE TUBE JOINTS

In this paper, the joint parameters derived from testing the new fully-bolted core tube beam-column joint were utilized in the finite element analysis of the complete frame structure. The static elastic-plastic time-history analysis of 8, 12, 16, and 20-story steel frames with the braces was carried out. By comparing the maximum inter-layer displacement angles in the X and Y directions when the frame yielded, the rationality of the brace arrangement and the applicability of the new fully-bolted core tube beam-column joints in the multi-story and high-rise steel frames were confirmed. After dividing the range of damage values for the steel frame with the new fully-bolted core tube beam-column joint, the seismic fragility and collapse resistance of the steel frame with the new fully-bolted core tube beam-column joint of different stories were analyzed. The results show that it is important to note that when the number of stories is low, the probability of each stage of the structure being exceeded is high. However, as the number of stories increases, the impact on the probability of the structure being exceeded gradually decreases. Under the action of a large earthquake peak acceleration, the exceedance probability based on a two-parameter damage index is higher than that based on a single-parameter damage index. This indicates that during the large deformation stage of the structure, the influence of cumulative damage on the evaluation of structural performance cannot be ignored. The steel frame of multi-story and high-rise buildings with new joints may be in a serious damage stage under rare earthquakes, and it is possible to collapse under the action of great earthquakes. In addition, the ACMR value of the structure under the action of rare earthquakes meets the evaluation criteria, while the ACMR value under the action of great earthquakes does not meet the requirements. Therefore, in practical engineering, it is necessary to take seismic strengthening measures to ensure that the structure has sufficient safety reserves against collapse during earthquakes.