Evaluation of Optimised Truss Models for FRP Shear Strengthened RC Beams

This paper presents the experimental work (1) to investigate the shear behaviour of RC beams strengthened with externally bonded shallow-angle CFRP laminate strips, and (2) to evaluate the efficiency of optimised truss model in shear resistance of CFRP strengthened beams. Two test series with a/d ratios of 2.16 and 3.70 were conducted. Each series consisted of four RC beams with different inclination of CFRP strips; namely 90, 45 and 25-degree. The results of the study showed that, depending on a/d ratio, shallow angle of CFRP strips gave much better performance in term of shear strength and deformation behaviour, compared with other conventional strengthening scheme. An optimised truss model, based on the principle of minimum strain energy theorem, was developed and used to predict the shear capacity as well as the anticipated failure mode of CFRP strengthened beams. It is shown that the proposed model can predict accurately the test results with coefficient of variation (COV) of only 4.14%. Compared to other shear model/method, the proposed model gave a better representation of the actual stress fields and behaviour.