ECC/RC组合梁受弯性能试验研究与分析

Experimental study and analysis of flexural behavior of ECC/RC composite beams

工程用水泥基复合材料(ECC)具有超高的韧性与优异的裂缝控制能力,提出采用ECC制作U型永久性模板,与混凝土形成外包式ECC/RC组合梁,以提高构件的力学性能和耐久性能.给出了ECC/RC组合梁受弯非线性分析方法,并开展了3种不同界面处理方式的ECC/RC组合梁的弯曲性能试验研究.结果表明,相比RC梁,ECC/RC组合梁的承载力和延性均有所提高;当荷载低于极限承载力的80%时,组合梁的最大裂缝宽度小于100μm;不同的界面处理对组合梁的极限承载力影响较小,但对延性系数有影响.试验结果验证了组合梁受弯非线性分析方法的正确性.基于ACI规范所采用的有效惯性矩法,提出了ECC/RC组合梁正常使用极限状态下挠度的简化计算方法,得到基于内力平衡的组合梁完全开裂截面的惯性矩公式,利用该简化方法计算得到的预测值与试验值吻合较好.

Engineered cementitious composite（ ECC） has ultra-high toughness and excellent crack controlling ability. A type of ECC/RC（ reinforced concrete） composite beam constructed with the U-shape permanent formwork made by ECC is proposed,in order to improve the durability and mechanical performance. A full-range nonlinear analysis method for flexural behavior of ECC/RC composite beam is presented,and three interface treatments of composite beam are designed to study the flexural behavior. Results indicate that,compared with RC beam,both the load bearing capacity and ductility of composite beam are increased. Furthermore,the crack width of composite beam is less than 100 μm when the applied load is lower than 80% of the peak load. The interface treatments in ECC/RC composite beams have little effect on the flexural strength,but they affect the member ductility to a certain extent. The calculated load-displacement curves by the proposed method are shown to be consistent with the test data. Based on the method of effective moment of inertia suggested by ACI code,a simplified calculation method of deflection for ECC/RC composite beam at the serviceability limit state is proposed,and the equations for the inertia moment of the full cracked section based on the internal force equilibrium are also obtained. The predicted deflection based on the proposed simplified calculation method shows good consistence with the experimental results.