Bond shear stress-slip relationships for FRP-NSM systems at elevated temperature

In the last years Near Surface Mounted (NSM) reinforcement has mainly been applied at ambient temperature, to strengthen reinforced concrete (RC) beams with FRP (fibre reinforced polymer) materials. Thereby, FRP bars/strips are embedded inside the concrete section by means of grooves filled with adhesive. The behaviour of FRP-NSM strengthening systems at elevated temperature is signicantly influenced by the type of adhesive (e.g. cementitious grout is usually more stable than epoxy resin at high temperature). To characterize the FRP-NSM behaviour two steps are needed: 1) shear tests performed in order to determine the FRP-concrete interaction via bond stress-slip curves and 2) constitutive bond stress-slip relationships for use in structural design (analytical and numerical). Hereby, the bond behaviour is to be considered temperature dependent. During two experimental campaigns, double bond shear tests were performed in order to study the behaviour of FRP-NSM systems at elevated temperature using different types of adhesive, epoxy resin and cementitious grout respectively. The bond shear stress-slip curves are discussed including the effect of different types of adhesive. Simplified bond stress-slip relationships are proposed to model the FRP-concrete interaction at high temperature.

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