End support connection of precast roof elements by bolted steel angles

Steel angles are extensively used to connect concrete floor/roof elements to the supporting beam in typical dry-assembled precast frame structures widely diffused in Europe and other parts of the world. These connections allow for relative rotation of the floor element in its vertical plane and restrains their relative displacement, avoiding possible loss of support and consequent fall of the floor element when the structure is subjected to lateral load. The diaphragm behaviour of the precast decks relies on these floor-to-beam connections. Their post-addition to unconnected floor-to-beam joints of existing buildings is a typical seismic retrofit intervention. All these applications are often made without an adequate information about the main structural parameters of the connections, due to lack of experimental or theoretical knowledge. An experimental campaign has been performed at Politecnico di Milano within the framework of the Safecast and ReLUIS research projects with the scope of characterising the mechanical behaviour of post-inserted floor-to-beam connections made with hot-rolled angles, cold-formed angles and welded sockets in the direction parallel to the floor element. The results of monotonic local tests on connectors and on the bolted connection with the floor rib and of cyclic and monotonic sub-assembly tests allowed to determine the main structural parameters of the joints, including elastic stiffness, strength, displacement capacity and hysteretic shape.