Sub-assemblage low damage connection incorporating blind-bolts and RBRFs subjected to cyclic loading

The Christchurch earthquake has given a renewed impetus to the development and use of low damage connections within moment-resisting frames in New Zealand. When using a low-damage technology, the building is designed to be easily repairable after a severe earthquake and is hence expected to be more resilient and cost-effective. This paper reports on a sub-assemblage test that investigates the behaviour of a newly proposed low damage connection between a steel beam and composite column. The connection incorporates blind-bolts, curved T-stubs and replaceable buckling restrained fuses (RBRFs). The RBRF is the only element which is allowed to yield when the earthquake level is higher than the design-based earthquake, so the establishment of a suitable strength hierarchy is vital to the success of the design. Two loading protocols have been applied using the same sub-assemblage but with a new RBRF at the start of each test; i.e. the RBRF was replaced after each test. The contributions of the connection, beam, and column to the total rotation have been summarised. The results show that a semi-rigid connection can be achieved by using this type of connection. Furthermore, an analytical approach has been proposed to predict the behaviour of this type of connection.