Simin Kohzadialvar - Graduated from the Faculty of Engineering, Yasin Boroujerd Institute of Higher Education. Borujerd, Iran.
Mehdi Komasi - Assistant Professor, Hydraulic Structure, Department of Civil Engineering, Faculty of Engineering, University of Ayatollah ozma Borujerdi, Borujerd, Iran.
Behrang Beiranvand - PhD. candidate in Civil Engineering, Water and Hydraulic Structures, University of Qom, Qom, Iran.

In a situation where terrorist attacks on civilian places and facilities are on the rise, the safe design of buildings against the impact loads caused by explosions is very important. Steel structures are very sensitive to heat and the pair of explosions and fire can cause progressive failure in such structures. Since explosion is usually associated with fire structures, in this study, the effect of the explosion on steel flexural frames under fire conditions was investigated. This study investigates two five-span frames of the same steel bending frame with differences in their height, one three and the other five-story, which explode under the TNT material at a distance of ۱۰ meters from the frame. The results of numerical calculations for the maximum impact pressure caused by the explosion, the duration of the positive phase of the explosion, and the duration of the negative phase of the explosion equal to ۰.۱ kgf/〖cm〗^۲ , ۳.۸۹ s, and ۰.۰۱۳۹ s, respectively, were entered into the modeling of Abaqus software. Three- and five-story frames were modeled on Abaqus software and subjected to the force of the explosive explosion outside the frame. To compare the explosion behavior of the two frames, stress analysis, displacement, roof floor acceleration, rotation, and work performed on the frame were performed. The minimum stress in a three-story frame (۹.۰۷ kgf/cm۲) is approximately ۲ times less than in a five-story frame (۱۷.۲۵ kgf/cm۲) and equivalent compressive loading has created less force in the three-story frame.

Explosion loading, Nonlinear behavior, steel bending frame, ABAQUS