Laboratory study of RBS connection using box-shaped replaceable link at the joint formation site

Before the occurrence of Northridge earthquake,it was believed that the conventional connections used in steel moment frame structures were capable of tolerating the great plastic rotation of 0.02 radians and above without a significant reduction in strength.Observation of the applied damages by the 1991 Northridge earthquake showed that the main damage was in the area of welded connections.For this reason and the weakness in welded connections,the idea of using the link area in steel connections has been proposed, which can be easily replaced after an earthquake.Therefore, in this study,the box-shaped linking element has been developed,which acts practically independent of the applied load and has a steady hysteresis behavior under tension and compression.In this research, laboratory numerical study has been conducted RBS connection using the box-shaped replaceable link at the joint formation site.For this purpose,first a validation based on a laboratory model has been performed in Abaqus software.In the following, models based on the validation paper have been developed and the idea of using a box-shaped link has been proposed.Two models have been developed and analyzed in Abaqus and two laboratory models have been examined experimentally.Two links with different details were placed in the area of reduced joint to reduce the beam section.The results show that very high stress concentration occurs in the box-shaped link area and other parts of the beam and column elements of the stress surface are less than the yield point and energy absorption is done in the box-shaped link area.It was also found that according to the maximum rotation recorded in the specimens and according to the AISC regulations, specimen A is one of the allowable connections in the middle frame and, model B has the necessary conditions to be placed in the permitted connections in a special moment frame (tolerating rotation of above 0.04 radians).