Numerical and analytical investigations of flexural behaviours of ECC–LWC encased steel beams

Abstract By conducting a series of experimental study, the authors recently demonstrated that engineered cementitious composites (ECC) can be employed to encase the compression flanges of structural steel sections to prevent slender flanges from local buckling and lateral torsional buckling of laterally unconstrainted beams. In this context, this paper presents comprehensive numerical and analytical investigations on the flexural behaviour of ECC-lightweight concrete (LWC) encased steel beams with a wide range of steel section geometry (from compact to slender) and steel grade (from normal strength to high strength). In the numerical study, a validated three–dimensional (3D) nonlinear finite element (FE) model was adopted to carry out a parametric study on the flexural capacity of 234 encased beams with different design parameters such as steel grade, ECC and LWC strengths, compactness of steel section, beam depth to width aspect ratio and flange and web thicknesses etc. Furthermore, an analytical model was developed by using the strain compatibility and force equilibrium conditions to predict the load-deformation curves of the encased beams until the flexural failure of the beams. Finally, in order to reduce efforts needed for day-to-day design, a simplified analytical solution was also proposed, and its accuracy was validated.