Abstract
A large share of reinforced concrete (RC) framed buildings is provided with wide beams being a type of beam allowing greater freedom in the architectural arrangement of interiors, beyond further advantage due to fewer formworks needed during the construction. Nevertheless, little attention has been devoted to the seismic vulnerability of this kind of framed RC buildings as well as to the study of strengthening systems purposely developed for wide beams and wide beam-column connections. Under these premises, this paper proposes simple strengthening solutions made by Fibre Reinforced Polymers (FRP) systems able to effectively improve seismic capacity through feasible arrangement suitable in case a wide beam is present. On the basis of wide beam-column joints previously tested without strengthening system, detailed nonlinear finite element models were calibrated. Then, an FRP strengthening intervention based on a brand new arrangement was modeled in order to perform additional simulations under seismic actions. This way, the effectiveness of the strengthening intervention was assessed finding out that significant strength and ductility increments were achieved with a relatively simple and cheap strengthening arrangement. Additional research would be desirable in the form of experimental tests on the simulated wide beam-column joints.
Highlights
Seismic safety of reinforced concrete (RC) structures is strongly dependent on the behavior of beam-column joints under reversed cyclic loads [1]
Using a meso-scale finite element model fitted on a database of 253 pull tests, they were able to develop local bond slip models with different level of complexity. Taking into account those experimental tests, they demonstrated that debonding of Fibre Reinforced Polymers (FRP) plates from concrete generally occurs in a thin layer of concrete with size ranging from 2 to 5 mm below the adhesive layer, they developed finite element models where the dimension of the finite elements near the concrete surface had a size one order of magnitude smaller than the fracture zone [35]
The research here presented is aimed at studying the seismic behavior of wide beam-column joints upgraded using CFRP laminates
Summary
Seismic safety of reinforced concrete (RC) structures is strongly dependent on the behavior of beam-column joints under reversed cyclic loads [1]. In [24], an experimental campaign on beam-column joints with conventional beam equipped with different solutions of FRP strengthening systems mixed with steel angles placed at the corners of the members was carried out These researchers highlighted some criticism related to the FRP strengthening configurations where a proper anchorage length is not available and mechanical anchorage are not used. The purpose of this study is to develop a brand new FRP-based strengthening technique for wide-beam-column joints taking into account the constraints related to the shape of the subassmblage and the connecting elements present in a real structure (slab, shallow spandrel beam). A finite element model has been developed and calibrated to reproduce the behavior of a control specimen previously subjected to experimental tests under cyclic loading This model has been updated with finite elements simulating the FRP laminates to evaluate the effectiveness of the proposed technique only by numerical simulations. Numerical results show appreciable strength increases and even much higher ductility increments provided by the strengthening intervention making this technique very promising in contributing to the reduction of RC frames’ seismic vulnerability
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