The brittle collapse of reinforced concrete (RC) structures built before the introduction of detailed seismic design codes (pre-1970’s) in recent earthquakes, has underlined the need for significant upgrades to the existing RC building stock. In particular, the observation of weak-column/strong-beam mechanisms, shear or bond failures have potentially catastrophic impacts that could be addressed by repair and retrofit solutions.
In recent years, retrofits with fibre reinforced polymers (FRP) have become increasingly popular due to the benefits of extended durability, corrosion resistance, and high strength-to-weight ratio and reduced labour time. Experimental evidence for the efficiency of such schemes for joint strengthening can be found in the literature. A previous study has shown that the reduced scale of most tested specimens, as well as the omission of slabs and transverse beams in many studies may lead to an unrealistic assessment of FRP retrofit schemes. In this study, realistic pre-1970’s full-scale interior beam-column joints with slab and transverse beams were tested under realistic conditions and cyclic lateral loading in order to propose and assess new, realistic FRP retrofit solutions for seismic actions.
Three CFRP retrofit schemes with selective retrofit objectives were devised aiming at improving the performance of inadequately reinforced RC beam-column joints. The retrofit schemes are composed of a combination of selective FRP strengthening and selective weakening components to ensure failure of the specimen according to capacity design principles. The objectives of the schemes were enhancement in lateral capacity, ductility enhancements, improved performance under repeated cyclic loading, as well as changing the failure mechanism.
Results from the full-scale cyclic tests on the CFRP retrofitted specimen are compared to the behaviour of a deficient specimen and a specimen designed to modern guidelines (EC 8). To evaluate the effect of the realistic set-up, the results are also compared to specimens without slab and transverse beams, highlighting their importance.
The work presented is supervised by Professor Tiziana Rossetto (UCL EPICentre), Professor Humberto Varum (Porto University) and Professor Dina D’Ayala (UCL EPICentre)
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