Maximum shear strength of concrete-encased steel composite beams: A novel strength model and FE verification

Due to the high load-carrying capacity and rigidity, concrete-encased steel (CES) beams are widely applied as transfer elements in heavily-loaded structures. However, the accurate shear strength prediction method is still under investigation because of the difficulty in the shear contribution decomposition of steel shape and reinforced concrete. Current design codes apply the strength superposition for CES beams, namely that their shear strength can be obtained by directly superimposing the shear strengths of RC and steel shape, which has been proven questionable by existing research. Therefore, it needs to carefully decouple the multiple shear transfer mechanisms in CES beams and explore their roles in a composite structure. In this paper, a novel shear strength model is proposed, in which a CES beam can be divided into a shear web and a composite truss consisting of RC with two steel flanges, and strain compatibility is applied to evaluate the shear contribution of these two parts. After that, an elaborate FE model is established to further quantitatively investigate the shear contribution of the composite truss and the shear web. Finally, the proposed model is verified with 61 existing specimens in the literature, and the comparison between the calculated and test results indicates that the proposed model could predict the shear strength of CES beams accurately.