Experimental and numerical study on steel-concrete composite frames with engineered cementitious composites

Engineered cementitious composites (ECC) is a type of cement-based material with the characteristics of tensile strain-hardening and multiple cracking. In this study, the structural behavior of the composite frame, whose crack resistance is improved by using ECC in the hogging moment region, was investigated. A large-scale steel-concrete composite frame with ECC at the beam end was designed and tested under vertical and lateral hysteretic loads. The test results were reported and compared with those of the traditional steel-concrete composite frame conducted by the authors in a previous study. The application of ECC notably reduced the crack width by 18%-40% in terms of the results under vertical loading cases and enhanced the ductility by 87% in the positive loading direction. The steel-concrete-ECC composite frame exhibited excellent seismic behavior with similar strength, stiffness, energy dissipation, stiffness degradation and strength degradation as the traditional steel-concrete composite frame. In addition, a nonlinear elaborate finite element (FE) model was established to simulate the tested frames, whose results agreed well with the test results. Furthermore, parametric studies on the ECC composite frames were performed via FE simulations, from which the influence of the ECC length, ECC tensile strength, ECC compressive strength and the steel beam height on the bearing capacity and cracking performance were clarified. The design method of the ECC length was also suggested. The test and FE results showed that ECC notably improved the slab anti-cracking performance. The study of this paper will provide a scientific basis for the application of ECC in steel-concrete composite frames to some extent.