End support connection of precast roof elements by bolted steel angles

Abstract

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

Seismic performance of precast concrete structures with energy dissipating cladding panel connection systems

“…The trend for increasing stiffness k p highlights a transition phase from a frame behavior to a wall behavior, for which higher stiffness k t is needed to make the frames vibrating in phase. It is worth noting that for traditional floor‐to‐beam connections the stiffness is in the range of 10 3 ÷10 5 kN/m …”

“…It is worth noting that for traditional floor-to-beam connections the stiffness is in the range of 10 3 Ä10 5 kN/m. 45 For k t = 0 (null diaphragm), the fundamental vibration mode with frequency equal to 0.91 Hz only involves the central frame (the participation mode is 30%), since the lateral frames vibrate independently. For low stiffness panelto-panel connections, the fundamental frequency is scarcely dependent on k t , since all frames have similar mass and stiffness.…”

Efficacy of roof-to-beam mechanical connections on the diaphragm behaviour of precast decks with spaced roof elements

“…The most typical floor-beam connections consist of angle brackets for TT elements and dowels for other types of elements, such as the wing-shaped ones [26,27]. Tests on typical and tailored floor-beam mechanical connections have been reported in [28] and [29], respectively. Tests on dowel connections are reported in [30][31][32][33][34][35].…”

“…For the comparison of the numerical model against the experimental results, an elastic stiffness of 25 kN/mm has been used to model the hot-rolled angle connections placed in the prototype. Such a value has been derived from the first elastic branch (pre-activation) observed in the tests described in [28].…”

“…The non-linear mechanical behaviour of the typical roof-beam connections has been calibrated on the basis of experimental evidence, so to investigate their role in the seismic performance of precast structures through non-linear dynamic analyses. From the test results described in [28], the experimental behaviour of post-inserted 10-mm thick hot-rolled angle brackets placed at both sides of a rib and connected through a bolt may be described with: More sophisticated hysteretic laws might better define the behaviour of this connection. However, reference has been made to common hysteretic laws available in most of the structural software used by practitioners.…”