Experimental Evaluation of Rigid Connection with Reduced Section and Replaceable Fuse

The connection with reduced beam section was proposed after the 1994 Northridge earthquake. Until then, it was generally believed that connections with complete groove welding can withstand large plastic deformations. However, the cracks and brittle failures taken place in connections revealed that the actual ductility in these connections might be lower than what was predicted by design codes. By forming a plastic hinge outside the joint, this connection reduces the damage inflicted upon the panel zone. It has to be mentioned, however, that due to the concentration of damage in the reduced area, the entire beam has to be replaced after average earthquakes that is practically impossible. The aim of this study is to experimentally investigate the use of the reduced section in a replaceable fuse. The column and the beam were chosen to be made of sections equivalent to IPE 240 and IPB 180 wide flange profiles and the cyclic quasi-static load was applied until a drift of about 9 percent. The hysteresis moment-drift diagram was drawn. The first sample was a reduced beam section with end plate and stiffeners (RBS). Under loading, this sample satisfied the criteria for the ductility of special moment resisting frame. However, due to the fact that after an average or strong earthquake damage concentrates in the beam and replacing it after earthquake is either extremely difficult or not possible at all, it was tried to use a short replaceable fuse at the end of the beam in the second and third samples. The second sample incorporated a fuse with the length of 35.5 cm and a beam with a reduced flange (RBS-F). Since the ratio of the width of the flange to the height of the beam is directly correlated to its resistance against lateral-torsional buckling, cutting the beam in RBS connections causes different types of buckling to occur faster. To overcome this problem, in the third sample, only the height of the beam was decreased and the dimensions of the flange were not altered. Therefore, the third sample included a 35.5 cm long fuse and a beam with a reduced web (RWS-F). All of the samples satisfied the required drift for the rigid connection special moment resisting frames and using different types of RBS connections reduces the damage inflicted upon the column and the panel zone. The results showed that in addition to having very suitable ductility, the RBS-F and RWS-F samples can be very good post-earthquake replacements for conventional RBS connections