组合加固足尺预应力混凝土箱梁抗弯性能试验

Flexural behavior experiment of full-scale PC box girder strengthened by composite technique

为解决危旧混凝土梁桥结构性能显著下降的问题,采用足尺试验研究了应用钢板-混凝土组合加固预应力混凝土小箱梁的抗弯承载性能;对2片20m跨径钢板-混凝土组合加固足尺梁进行抗弯承载性能试验,并与1片未加固足尺梁和1片预应力CFRP加固足尺梁的抗弯承载性能试验结果进行对比,分析了足尺预应力混凝土小箱梁组合加固后的抗弯性能,研究了加载全过程跨中截面的加固钢板、原梁主筋、顶板混凝土和钢筋与连接构造的应变变化规律;基于足尺试验结果,建立了钢板-混凝土组合加固预应力混凝土小箱梁抗弯承载力简化计算公式。研究结果表明:钢板-混凝土组合加固梁在破坏时表现出明显塑性破坏特征;与未加固梁相比,钢板-混凝土组合加固足尺试验梁的极限承载力实测值提高了76%以上,在正常使用阶段下的刚度提高1倍以上,因此,组合加固能显著提高预应力混凝土箱梁的承载性能;受力过程中试验梁跨中截面应变分布符合平截面假定;组合加固部分与混凝土箱梁腹板纵向相对滑移小于0.6mm,因此,钢板-混凝土组合加固后的试验梁整体工作性能较好;足尺试验得到的极限承载力与简化公式计算结果的比值分别为1.06和1.01,因此,简化公式可靠,可用于组合加固预应力混凝土箱梁的承载性能计算与分析。

In order to solve the problem of declining structural performance of old concrete girder bridges,a full-scale test was conducted to investigate the flexural behavior of small PC box girders strengthened by the steel plate-concrete composite strengthening(SPCCS)technology.Two full-scale 20 m-span small PC box girders strengthened by the SPCCS technique were tested to research their bending properties,the test result was compared with the full-scale test results of an unstrengthened girder and a prestressed CFRP(carbon fiber reinforce plastic)strengthened girder,the flexural behavior of full-scale SPCCS box girders was analyzed,and the straindistributions of strengthening steel plates,major reinforcements of original girder,concrete and reinforcements at the top flange,and connection sturctures at the mid-span section in the whole loading process were studied.Based on the full-scale test results,the simplified calculation formulas of flexural capacity of SPCCS full-scale small PC box girder was established.Research result shows that the SPCCS girders fail in the plastic flexural mode.Compared with the unstrengthened girder,the measured ultimate flexural capacity of SPCCS full-scale test beam increases by more than 76%,and the stiffness in normal usage stage increases by more than1 time,therefore,the composite strengthening can obviously improve the flexural capacity of PC box girder.The strain distribution of mid-span section for test girder is in accordance with the plane cross-section assumption.The longitudinal relative slip between the composite strengthened part and the web of concrete box girder is less than 0.6 mm,therefore,the SPCCS girder has good integral working performance.The ratios of the measured and calculated ultimate flexural capacities of 2 full-scale test girders are 1.06 and 1.01,respectively,so the simplified formulas are reliable and can be used to calculate and analyze the bearing capacity of PC box girder strengthened by the composite strengthening.