Investigation the cyclic behavior of rigid RBS connections with horizontal and vertical stiffeners in steel moment- resisting frame

In this study, RBS connections behavior reinforced by horizontal and vertical stiffeners are assessed under cyclic loading and the effect of stiffeners is studied in order to improve the cyclic behavior of connections. The finite element ABAQUS software has been used to verify and simulate reduced beam section (RBS) connection behavior. Parametric study have been conducted by changing the stiffeners number, material and arrangement in connection area. The finite element analyses results showed that when using a combination of two horizontal and two vertical stiffeners, the initial and ultimate strength of the connection have been increased by 6.2% and 26.1%, respectively, compared to that of the connections without stiffeners. When using horizontal and vertical stiffeners in a rectangular arrangement with a length equals to 75% of the section reduction area length and its height equals to 75% beam height, the initial and ultimate strength of the connection has been increased by 6% and 20%, respectively in comparison the state without stiffeners. By comparing the use of ST37 and ST52 in stiffeners, it has been observed that both used steels have the same effect on the connection strength. Meanwhile, the effect of steel material of stiffeners could be ignored on improving the connection strength.