U型箍加固锈蚀RC梁的抗弯性能试验研究及数值分析

为研究U型箍加固和二次锈蚀对锈蚀RC梁力学性能的影响，该文通过设计7片试验梁，分析构件的应变规律、变形特征、破坏机理等，并采用ABAQUS有限元软件进行了数值模拟，探讨U型箍加固厚度与加固位置对加固梁性能的影响。结果表明，试验梁跨中截面应变满足平截面假定，中和轴高度大致符合这个规律:锈蚀梁以及锈蚀加固再锈蚀梁的中和轴高度均要大于加固锈蚀梁的高度；荷载增大到一定时，U型箍的锚固作用开始发挥作用；加载中后期，同侧三片U型箍分担的剪力存在不均匀性；腐蚀不均匀导致两端的U型箍应变增长规律有差异；加固梁、加固锈蚀梁的裂缝更稀疏，裂缝趋向于跨中区域分布，斜裂缝逐渐变得不明显； U型箍加固梁的开裂荷载与极限荷载有所提高，塑性特征更为明显，主要呈现为弯剪破坏；二次锈蚀和不均匀性会改变构件变形发展，影响梁的破坏形态。数值模拟的极限荷载、极限荷载对应的挠度以及能量吸收值与试验结果的误差分别在4.22%、9.7%、9.9%范围以内，设置3 mm的加固厚度对提高承载力较为适宜，U型箍布置在梁端位置可更好地提高构件的强度和刚度。

EXPERIMENTAL STUDY AND NUMERICAL ANALYSIS OF CORRODED RC BEAMS STRENGTHENED WITH U-SHAPED PLATE

In order to investigate the effect of strengthening with U-shaped plate and secondary corrosion on the mechanical properties of corroded RC beam, 7 pieces of test beams were designed to analyze the strain law, deformation characteristics, failure mechanism, et al. By using the ABAQUS finite element software, numerical simulation was carried out to study the influence of thickness and strengthening position of U-shaped plate on the performance of the strengthened beam. The results show that strain distribution of the mid-span for the test beams satisfies the plane-section assumption. The height of the neutral axis is roughly in line with the law:the height of neutral axis of the corroded beams and the corroded-strengthened-corroded beams is higher than that of the corroded reinforced beams. When the load increases to a certain extent, the anchoring effect of the U-shaped plate starts to work. In the middle and late stage of loading, the shear force shared by the three U-shaped plates on the same side is uneven, and the uneven corrosion leads to the different strain growth of U-shaped plate at both ends. The cracks of both strengthened beams and those with secondary corrosion appear more sparsely, which tend to locate in the middle span region, while the inclined cracks gradually become less obvious. The cracking load and the ultimate load of beams strengthened with U-shaped plates are improved, and the plastic characteristics are more obvious, which mainly exhibit bending-shear failure. The secondary corrosion and inhomogeneity change the deformation of components, which affects the failure mode. Compared with experimental results, the error of the ultimate load, the deflection of the ultimate load and the energy absorption value of numerical simulation results were in the range of 4.22%, 9.7% and 9.9%, respectively. It is more suitable to improve the bearing capacity by adopting a reinforcement thickness of 3 mm, and the strength and rigidity of the structure can be improved by arranging the U-shaped plate at the beam ends.