Computational modelling and analytical model for two-step corbel for precast concrete system

Abstract

Two-step corbels can improve the industrial production of precast concrete structures and reduce the openings and cut-outs in the formwork. In the two-step corbel system analysed in this paper, fully anchored threaded couplers are placed in the column mould and used in a second stage to splice the main reinforcement of the corbels. Thirty-four specimens with a monolithic corbel or a two-step corbel were previously tested and reported in another publication. The main variables analysed are the different treatments of the column–corbel interface, the presence of loop reinforcement normal to the interface and the addition of steel fibres to the concrete of the corbel. In this paper, the experimental results are used to calibrate a 3D non-linear finite element model developed on the DIANA® package. The experimental results are also compared with normative models used to predict the strength of monolithic corbels. Based on the experimental results and computational models, an analytical model, derived from analytical models available in the literature, is proposed. The main conclusions of this research are: a) the difference in the yield strength and the ultimate load of the two-step corbels obtained from tests and computational modelling is less than 10%, b) normative models developed for monolithic corbels cannot estimate the resistance of the two-step corbels with an error less than 10%, c) the statistical parameters of the proposed analytical model for two-step corbels with steel fibres and without secondary reinforcement present a bias factor and CoVME equal to 0.887 and 0.161 to estimate the yield strength, and 1.021 and 0.222 to estimate the ultimate load, and d) a proposed analytical model for evaluating the crack width at the interface between the two-step corbel and column presented a good correlation with the cracking observed in the tests.