Flexural behaviour of ECC-LWC encased slender high strength steel composite beams

This paper reports an experimental and numerical study on the flexural behaviour of Engineered Cementitious Composites and Lightweight Concrete (ECC-LWC) encased slender High Strength Steel (HSS) composite beams. Four simply supported slender HSS composite beams with different encasement materials (concrete or ECC-LWC) and configurations (fully or partially encased) were first tested under four-point bending. Three-dimensional nonlinear finite element (FE) models were then developed and validated against the test results. Experimental results obtained showed that the two ECC-LWC fully encased slender beams carried higher loading with improved ductility than the concrete fully encased slender beam. Moreover, test results of the ECC-LWC fully encased slender beams confirmed that the encasement successfully eliminated both local buckling and global lateral torsional buckling of the slender HSS I-section. However, the partially encased beam in which encasement was only applied to the compression flange was failed by lateral torsional buckling before its top flange was yielded. A parametric study was also carried out using the validated FE model to further investigate the effectives of different encasement parameters on the flexural behaviour of ECC-LWC fully encased slender HSS composite beams. Finally, a simplified analytical solution is proposed for estimating the flexural strength of the fully encased beams.