钢-UHPFRC组合加固足尺混凝土T梁抗弯承载性能试验

Flexural behavior tests of full-scale concrete T girders with steel-UHPFRC composite strengthening

为恢复地震、爆炸、火灾等极端荷载作用后混凝土T梁桥上部结构的抗弯性能,利用超高性能纤维混凝土(UHPFRC)材料的良好抗弯拉性能改进钢-混凝土组合加固技术,提出钢-UHPFRC组合加固方法。以带损伤的足尺混凝土T梁为试验研究对象,通过抗弯承载性能试验,分析钢-混凝土组合加固和钢-UHPFRC组合加固T梁在正常使用阶段的受力性能和承载能力极限状态下的弯曲破坏模式;基于足尺试验弯曲破坏形态,建立钢-UHPFRC组合加固足尺混凝土T梁抗弯承载力计算图示和简化公式。研究结果表明:钢-UHPFRC组合加固试验梁发生塑性弯曲破坏;跨中横截面变形符合平截面假定,加固部分与原结构之间纵向相对滑移小于0.35mm,加固后试验梁整体工作性能较好,与未加固梁相比,钢-混凝土组合加固T梁抗弯极限承载能力可提高71%;在加固材料质量减轻50%的条件下,钢-UHPFRC组合加固T梁抗弯极限承载能力可提高30%,正常使用阶段其抗弯刚度与钢-混凝土组合加固T梁相近,因此钢-UHPFRC组合加固可提升或恢复混凝土T梁的抗弯承载性能,同时降低加固材料对结构自重的增加;抗弯承载力简化公式计算值与钢-混凝土组合加固T梁和钢-UHPFRC组合加固T梁试验值的比值分别为0.97和0.95,简化公式计算可靠,可用于组合加固后混凝土T梁桥的设计计算。

To recover the flexural behavior of the superstructure in concrete T-girder bridges after damage under extreme loads such as earthquake,explosion,and fire,the steel-UHPFRC composite reinforcement method,which improves the steel-concrete composite reinforcement technology by using the excellent flexural performance of the UHPFRC material,was proposed.The experimental research was conducted on damaged full-scale concrete T-girders.The flexuralbehavior under the normal performance stage and the bending failure mode at the bearing capacity limit state of both steel-concrete composite strengthened T-girder and steel-UHPFRC composite strengthened T-girder were experimentally analyzed by bending tests.Based on the bending failure mode of full-scale T-girders,the bending capacity calculation diagram and simplified formula of steel-UHPFRC composite strengthened concrete T-girders were established.The results show that plastic bending failure of the steel-UHPFRC composite strengthened test girders.The cross-section deformation of the girders conforms to the flat section assumption.The longitudinal relative slip between the reinforcement and the original structure is less than0.35 mm.Compared to the unstrengthened girders,the strengthened test girders demonstrate an overall improvement in the working performance.It is observed that the ultimate flexural capacity of the girder increases by 71%after strengthening with steel-concrete composite.Under the condition that the weight of the reinforcing material is reduced by 50%,the ultimate flexural capacity of girder strengthened with steel-UHPFRC composite can be increased by 30%.Further,the flexural behavior of the steel-UHPFRC composite reinforced concrete T-girder is similar to that of the steel-concrete composite reinforced concrete T-girder under the normal performance stage.Therefore,the steel-UHPFRC composite reinforcement can improve or restore the flexural capacity of the concrete T-girder and reduce the weight of the reinforcement,which contributes to the self-weight of the structure.The values of simplified bending capacity obtained from the theoretical analysis and the experimental results are compared for both the steel-concrete composite reinforced girder and steel-UHPFRC composite reinforced girder,and the ratios of the values for the girders are found to be 0.97 and 0.95,respectively.Thus,the simplified calculation formula is reliable and can be used in the design calculations of composite reinforced concrete T-girder bridges.