Flexural behaviours of Engineered Cementitious Composites – High strength steel composite beams

Abstract

Since the compressive strain of normal strength concrete (NSC) (0.23 – 0.3%) is too low to work compatibly with high strength steel (HSS) with typical yield strain greater than 0.35%, Engineered Cementitious Composites (ECC) which generally has a minimum compressive strain of 0.5%, is an attractive alternative to replace NSC when constructing composite beams using HSS sections. This study investigated experimentally the flexural behaviours of composite beams comprising HSS I-section and hybrid Polyethylene-steel fibres (PE-ST) ECC slab. Shear interactions between the HSS beam and the PE-ST ECC slab was provided by normal profiled steel sheeting (PSS) and headed shear studs. Four composite beams including three ECC-HSS beams and one NSC-HSS beam were tested under four-point bending until failure. The test results indicated that while the flexural capacity of ECC-HSS beams only showed a slight improvement, its ductility was significantly enhanced when comparing with the NSC-HSS beam. All ECC-HSS beams failed in a ductile manner and gradual softening behaviours were observed after the peak load. In contrast, the NSC-HSS beam showed a less ductile failure mode with a sudden crushing of NSC and a sharp drop of bending resistance after the peak load. To complement the test results, a 3D nonlinear finite element (FE) model was also developed and validated against the experimental results. Well agreements between the FE and test results were observed. This confirmed that the FE model could be employed to evaluate the general behaviours of ECC-HSS composite beams.