Today, many dangers threaten building structures. Many abnormal loadings are not considered in the design of structures. The sudden removal of the column can occur as a result of mistakes caused by construction, explosion, impact or any other unusual cause in the structure. In steel structures, steel frames, as one of the main components of the structure, play an important role in the safety and durability of the structures. However, progressive failure in steel frames causes problems for structures due to arbitrary deformation. The purpose of this research is to investigate the effect of using converging braces in increasing the durability and safety of steel structures against progressive failure. In this research, SAP2000 software and non-linear analysis have been used in terms of the effects of non-linear geometric deformations, in order to model and examine the behavior of connections in numerical analysis. By examining 3, 8 and 12 story structures with and without column removal, it was determined that they were modeled with three types of cross braces, seven and eight. The results showed that in the model of the 3-story structure with cross bracing, the displacement was reduced by 63% compared to the model without braces and without progressive failure. Also, in the model of the 8-story structure with cross braces, there was a 38% reduction in displacement compared to the model without braces and without progressive failure, and in general, the 12-story structure model with cross braces had a 23% reduction in displacement compared to the model without braces and without progressive failure. .

Research in the field of using converging braces in steel structures, due to its importance in increasing the strength and safety of structures, has been noticed. Considering that the research topic of investigating the effect of convergent braces on the strength of steel frames in progressive failure is one of the most important topics in the field of steel structures. Considering that progressive failure in steel frames can cause serious risks for people and high damages for structure owners, the use of converging braces is considered as an important solution to prevent progressive failure. In addition, considering that the use of converging braces in steel structures requires high costs, determining cost optimization and optimal use of converging braces is also one of the important goals of this research project. By determining the optimization of costs and the optimal use of converging braces, it is possible to reduce the costs of building the structure and increase the efficiency of using converging braces in steel structures. With the studies conducted and the investigations carried out in the field of the possibility of the vulnerability of today's buildings in the cities against progressive deterioration and that the majority of the existing buildings are not capable of dealing with such a phenomenon and are vulnerable to progressive deterioration, so the purpose of this conclusion The message is to seek to improve this situation by providing a solution and to help those buildings that have been built, but in their designs, the characteristic loading of progressive failure has not been included. In this project, three-, eight-, and twelve-story steel buildings with bending frame were evaluated with the help of SAP2000 software and in three-dimensional form with the influence of various factors such as the type and shape of converging braces, and these evaluations were done with the help of non-linear static analysis. And the results are presented in the form of tables and diagrams, which include the formation of plastic joints of the members in all three structures, comparing the sturdiness of the structures, checking the vertical displacement of the desired top node and comparing between different models, as well as checking and controlling the relative lateral displacement of the floors.

1. Investigating the effect of using converging braces in increasing the strength and safety of steel structures against progressive failure.

2. Determining the optimal type, shape, and converging braces to increase the strength of steel frames and prevent progressive failure.

3. Cost optimization and optimal use of converging braces in steel structures, in order to reduce the cost of building the structure and increase the efficiency of using converging braces in steel structures.

4. Investigating the changes in the behavior and strength of steel structures using converging braces in progressive failure.

5. Using numerical simulations with the help of SAP2000 software, in order to determine the best type and shape of optimal convergent braces.

Today, the discussion of passive defense and increasing the flexibility and strengthening of structures against explosions, collisions and impacts is one of the main concerns of government organizations around the world, including Iran. It has progressed to failure.