CFRP筋增强ECC梁弯曲性能试验研究

为研究碳纤维增强树脂复合材料(Carbon fiber reinforced polymer，CFRP)筋/超高韧性纤维增强水泥基复合材料(Engineered cementitious composite，ECC)梁的抗弯性能，对3根CFRP筋/ECC梁、1根玻璃纤维增强树脂复合材料(Glass fiber reinforced polymer，GFRP)筋/梁和1根CFRP筋混凝土梁进行了四点弯曲试验，分析了配筋率、纤维增强树脂复合材料(Fiber reinforced polymer，FRP)筋类型和基体类型对梁抗弯性能的影响。试验结果表明:CFRP筋/ECC梁与GFRP筋/ECC梁和CFRP筋混凝土梁类似，均经历了弹性阶段、带裂缝工作阶段和破坏阶段；配筋率对CFRP筋/ECC梁的受弯性能影响较大。随着配筋率的增加，CFRP筋/ECC梁的承载能力不断提高，延性性能逐渐减弱；ECC材料优异的应变硬化能力和受压延性，使得CFRP筋/ECC梁的极限承载能力和变形能力均优于CFRP筋混凝土梁；由于ECC材料多裂缝开裂能力，CFRP筋/ECC梁开裂后，纵筋表面应变分布比CFRP筋混凝土梁更均匀； 由于聚乙烯醇(Polyvinyl alcohol，PVA)纤维的桥联作用，CFRP筋/ECC梁破坏时，其表面出现了大量的细密裂缝，且能保持较好的完整性和自复位能力；正常使用阶段，CFRP筋/ECC梁的最大弯曲裂缝宽度均小于CFRP筋混凝土梁。最后，根据试验结果，建立了基于等效应力图的CFRP筋/ECC梁弯曲承载力简化计算模型，确定模型中的相关系数。由简化模型计算的极限承载力与试验结果具有较好的相关性。 

Experimental study on flexural performance of ECC beams reinforced with CFRP bars

To study the flexural performance of engineered cementitious composite (ECC) beams reinforced with carbon fiber reinforced polymer (CFRP) bars, four-point flexural experimental investigates were carried out on three ECC beams reinforced with CFRP bars, one ECC beam reinforced with glass fiber reinforced polymer (GFRP) bars and one concrete beam reinforced with CFRP bars. The main parameters were the reinforcement ratios, the reinforcement type and the matrix type. The experimental results show that the load-deflection curves of ECC beam reinforced with CFRP bars are similar with the ECC beam reinforced with GFRP bars and concrete beam reinforced with CFRP bars, which have an elastic stage, a working stage with cracks and a failure stage. The reinforcement ratio has a great influence on the flexural performance of ECC beams reinforced with CFRP bars. With the increase of reinforcement ratio, the ultimate bearing capacity of ECC beams is improved, and the ductility performance is gradually weakened. The excellent strain-hardening ability and ductility of ECC materials make the ultimate bearing capacity and deformation of ECC beams with CFRP bars superior to the concrete beam reinforced with CFRP bars. Based on the multi-cracking ability of ECC, the strain distribution on the surface of longitudinal bars is more uniform than that of concrete beams with CFRP bars after cracking. Due to the bridging effect of polyvinyl alcohol (PVA) fiber, a large number of fine cracks appear on the surface of ECC beams reinforced with CFRP bars. When ECC beams reinforced with CFRP bars fail, it could maintain good integrity and self-recovering ability. In service stage, the maximum crack width of reinforced ECC beams presents smaller than that of concrete beams. Finally, a simplified calculation model for ultimate bearing capacity of ECC beams reinforced with fiber reinforced polymer (FRP) rebars is proposed, predicting good agreement with the experimental results.