Investigation of different methods in strengthening braced steel frame under blast load

Unpredicted loading caused by blast or impact may lead to severe damage in structures. Such damage may affect the whole structural performance. Connections are the key contributor to the integrity and energy dissipation capacity of the structural steel systems and play the most important role in mitigating such consequences. In the view of the importance of connections, finite element analysis is used in this paper to study the behavior of braced steel frame under blast loading using ABAQUS finite element software. This Frame is adopted from a hospital building. Firstly, the behavior of the frame is investigated under near-field blast load to locate the regions that are susceptible to damage. Then according to the damage, five different possible reinforcing scenarios are proposed, and the advantages and drawbacks of each one are investigated. It is observed that asymmetrical deformations and damages are notable due to the front members’ severe local damage. The damage in the structure decreases rapidly as the height increases. In addition, the vertical web stiffeners and triangular plates on the top and bottom flanges eliminate the severe plastic strain and stress concentration in the connection zone causing the critical regions to move toward the middle of the beam that is desirable. It is also observed that continuous reinforcement of the beam webs with web sheets on both sides, significantly reduces the stresses on the web. This is a more effective way than the web stiffeners because of fewer stress changes in other members due to minor changes in the stiffness of the connected members.