【摘要】 为了解先张法折线预应力混凝土梁预制过程中钢绞线张拉-放张所产生的预应力损耗和整体结构受力特性，设计、制作2片长30 m的先张法折线预应力混凝土I形梁足尺模型进行钢绞线张拉及放张试验，分析不同弯起角度钢绞线在张拉过程中的预应力摩阻损失、放张过程中的梁端构造力学行为和有效预应力传递长度。结果表明：钢绞线张拉过程中的预应力摩阻损失与弯起角度正相关，与拉板式弯起器间滑动摩阻系数为0.23;钢绞线放张过程中梁端腹板最大主拉应力超过C50混凝土抗拉强度设计值，需进行腹板局部加厚处理，其余位置均不超过设计值；锚固区内直线钢绞线有效预应力传递长度约为77 cm,显著低于《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)中后张法预应力钢铰线传递长度计算值，预应力传递效果较好。更多还原

【Abstract】 This study investigates the prestress loss and the overall load bearing behavior of the prestressed concrete(PC)girder with pretensioned deflecting steel strands during the tensioning-detensioning process of the steel strands.Two full-scale PC I girder specimens of 30 m in length were prepared for the steel strands tensioning-detensioning test.The parameters related to the steel strands with different deflection angles, including prestress friction loss during the tensioning process, mechanical property of girder-end details during detensioning process and the effective prestress transfer length, were analyzed.The results demonstrate that the prestress friction loss of the steel strands is in positive correlation with the deflection angle.The slip friction coefficient between the steel strands and the plate bender is 0.23.The maximum principal tensile stress of the girder-end web during the detensioning of steel strands surpasses the design tensile stress of the C50 concrete, indicating that the web should be thickened, while the stress in the remaining area is below the design value.The effective prestress transfer length of the straight tendons in the anchorage zone is about 77 cm, remarkably lower than the value suggested in the Specifications for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG 3362-2018),indicating sound prestress transfer effect.更多还原