Flexural behaviour of steel composite beams encased by engineered cementitious composites

In this study, the flexural behaviour of a new form of Engineered Cementitious Composite (ECC) - Light Weight Concrete (LWC) encased steel composite beams is studied. Four simply supported ECC-LWC encased steel composite beams were tested to investigate the effects of ECC cover thickness on the ultimate load carrying capacities and failure modes. The test results indicated that the ductility of ECC enhanced the residual strength of encased steel member even after the crushing of the top ECC cover. It is demonstrated that the structural performance of traditional steel-concrete composite beams could be improved by replacing normal concrete with ECC and LWC as the encasing materials. In addition to flexural strength enhancement, it is found that the combined use of ECC and LWC could improve the overall ductility of the beams and reduce their weights. To complement the experimental study, a three-dimensional nonlinear finite element model is developed to simulate the behaviour of ECC-LWC encased steel composite beams. The model was validated by comparing the numerical results to the experimental results. A parametric study was then conducted using the model to investigate the influence of the ECC compressive strength, the ECC tensile strength, the LWC compressive strength and the steel yield strength on stiffness, flexural resistance and ductility of ECC-LWC encased steel composite beams.