The modified spring‐stiffness model for welded simple connection at elevated temperature

The outbreak of fire events in high‐rise buildings in recent years and the vulnerability of steel structure buildings, which leads to partial or complete failure of structures, clearly illustrate the need for designing such buildings against fire. The first step in fire design of structures is to have access to simplified equations for analyzing structural components against fire. Regarding this issue, to provide moment‐rotation relationships for designing welded seated angle connections, a modified spring stiffness model is presented in this article. In this method, the effective connection components are represented as springs with certain strength and stiffness properties that change as the temperature changes. Considering the special effect of welds on the behavior of these types of connections, separate springs for each section of the welds are considered and the effects of temperature on welds and base metal are taken into account. Comparing the results obtained from the proposed formulas with those of the tests, as well as the numerical analysis results, shows that the results in this method can be provided fast and accurately.