环向预应力钢绞线加固RC拱肋力学性能试验

通过RC方柱偏压试验和RC拱肋面内受力全过程试验，对环向预应力钢绞线（LPSW）加固拱桥方法进行研究。对相对偏心距分别为0，0.25，0.5的3类RC方柱进行偏心受压试验，偏心试验表明：RC方柱加固后，预应力钢绞线先于箍筋约束混凝土，有效抑制了混凝土裂缝的纵向开展，预应力钢绞线及箍筋之间具有良好的变形协调性；LPSW加固柱承载力提高了3%～34%，LPSW加固技术适合于小偏心受压结构，偏心距越小，增强效果越明显。在偏压试验基础上，拓展了LPSW加固RC拱肋的模型试验，对LPSW加固模型拱荷载-挠度曲线、截面应变和结构破坏模式等方面进行分析。拱肋试验表明：LPSW拱肋受力过程和破坏模式与RC拱肋相似，分为弹性阶段、裂缝开展阶段和钢筋屈服阶段，最终因出现5个塑性铰形成机构而呈塑性破坏。由于环向预应力钢绞线约束，使RC拱肋提前处于3向受压应力状态，横向膨胀受到约束，避免拱肋出现拉应力，加固拱肋的初裂荷载、钢筋屈服荷载和极限荷载为未加固拱的2倍、1.6倍和1.47倍。基于偏压柱及拱肋试验结果，利用弹塑性失稳理论的等效梁柱法，建立LPSW加固拱肋极限承载力的计算公式，计算值与试验值吻合较好，且偏于安全，可用于评估实际加固拱桥的承载能力。

Experiment on Mechanical Properties of RC Rib Arch Strengthened with Lateral Prestressed Steel Wire

A technique for reinforcing arch ribs with lateral prestressed steel wire (LPSW) was studied by f testing the process behaviors of RC arch ribs under in-plane load and RC square columns under eccentric load. The eccentric compression tests of the RC square columns were performed with relative eccentricities of 0, 0.25 and 0.5. Results show that prestressed steel wire prior to stirrup restrained concrete, which effectively inhibits the development of longitudinal cracks in the concrete, and has a good deformation coordination with the stirrup after reinforcement of RC square column. The ultimate bearing capacity of the strengthened columns are 3% and 34% greater than those of the contrast columns. Using LPSW increases the strength in small eccentrically loaded columns, an effect which strengthens as the eccentricity decreases. Based on the eccentric compression test, a test was carried out on an RC rib to analyze the load deflection curve of the arch, the strain of the section and the failure mode of the structure of the LPSW reinforcement model. The result of the arch rib test shows that the defect propagation of LPSW arches are similar to RC arches. The process can be divided into the elastic stage, crack development stage and reinforcement yield stage. The LPSW arches also fail because of the mechanism formed by five plastic hinges caused by cracks in tensile areas. The effects of LPSW confinement mean that the RC arches first go under triaxial compression, constraining the lateral expansion to avoid the tensile stress of the arch rib. The initial crack load, yield load, and ultimate load of the reinforced arches are 2, 1.6, and 1.47 times that of the unreinforced arches, respectively. Utilizing the equivalent beam-column method based on the elastoplastic instability theory, the formula for calculating the ultimate bearing capacity of LPSW reinforced arches is established on the basis of the test results of the eccentric columns and arches. The calculated results are shown to be in reasonable agreement with test results and can be used to evaluate the actual bearing capacity of a reinforced arch bridge.