Strengthening RC beam–column connections with FRP strips

Abstract

Reinforced concrete connections, designed prior to the implementation of earthquake design standards, may be vulnerable to shear failure during a seismic attack. Addition of externally bonded fibre-reinforced polymer (FRP) composites can enhance not just the shear capacity but the deformation and energy absorption capacity of the connection. The majority of research studies to date have opted for complete or near-complete coverage of the joint region with FRP and have subjected the test specimens to cyclic (push–pull) loading. Such strengthening schemes and method of loading make it quite difficult to accurately monitor and hence understand the behaviour of the FRP and the concrete beneath. This paper presents results of a series of tests on the strengthening of shear deficient connections with FRP strips subjected to either cyclic or monotonic loading with the primary motivation being accurate description of the behaviour of the FRP. The tests also enable the failure modes to be more accurately reported and classified especially due to the use of monotonic loading. An analytical model is finally presented which accurately describes the mechanics of the FRP strengthening with the model predictions correlating reasonably well with the test data.