Increasing the defense capability of steel structures by determining optimal steel connections against blast load and providing methods to improve their performance

In this study, the numerical investigation of the pre-approved connections of the 10th topic of the National Building Regulations under explosive loading was done. For this purpose, six three-story, two-span frames with different connections were examined. These frames had similar beams and columns, and their connection types differed. The results showed that the frame with a bolted unstiffened extended end-plate connection (BUEEP) had the minimum displacement and optimal performance under explosive loading. Also, the frame with the reduced beam section connection (RBS) had the highest displacement and the weakest performance. Decreasing or increasing the number of floors did not affect the optimal performance of the frame with a bolted unstiffened extended end-plate (BUEEP) connection. To improve the performance of these connections, various methods were investigated. It was found that adding a steel plate with a thickness of 1 cm to the center of the column and the two ends of the beams separately reduced the maximum displacement of the frame by 11 and 5%. Meanwhile, adding a steel plate with a thickness of 1 cm to the two ends of the beams and the middle of the column at the same time caused a 15% reduction in displacement at the level of the third roof of the frame, which is a very suitable method to improve the performance of connections against explosion.