Experimental research and FEA on bearing capacity under negative moment of steel-concrete-ECC composite beams

In order to solve the problem that it is hard to control the cracking of the slabs under negative bending moments, a novel type of steel-concrete-ECC composite bridge structure was proposed for the negative-moment area of continuous composite beam bridges. Replacing the concrete on the surface with a certain thickness with hybrid fiber ECC can improve the durability of the continuous composite beam bridge in the negative-moment area. The static monotonic loading test of two steel-concrete-ECC composite beams and one steel-concrete composite beam was designed and completed. The study shows that with the same longitudinal reinforcement, the yield and ultimate load of the composite bridge structure with ECC are higher than that of the traditional composite structures, the cracking load is much higher, and the number and width of cracks are also reduced. Based on tests, the calculation method of the negative-moment bearing capacity of the composite beam in GB 50017-2017 ‘Standard for design of steel structures’ was modified and verified, and the results were in good agreement with the tests. The ABAQUS software was employed to establish finite element (FE) models of the steel-concrete-ECC composite bridge structure and the experimental simulation and parametric analysis were carried out. It is indicated that as the thickness of ECC increases, the improvement efficiency of each index decreases. The reinforcement ratio is proportional to each index. Under the short-term load, the cracking load of the two-layer reinforced composite beam is close to that of the three-layer reinforced beam, but the yield and ultimate loads are obviously improved. © 2022 Science Press. All rights reserved.