体外预应力节段预制胶拼梁抗弯极限承载能力模型试验研究

为研究体外预应力节段预制胶拼梁的抗弯极限承载能力和破坏模式,以某3×30m一联连续箱梁桥为背景,以偏不利的实桥中跨为研究对象,根据相似理论,设计制作了一跨缩尺比为1∶3的10m简支工字型试验梁,按照设计承载能力极限状态跨中最大正弯矩荷载组合和活载超载2个阶段进行了分级加载试验。结果表明:跨中最大正弯矩工况下,梁体强度和刚度满足设计要求,结构整体受压,处于弹性受力状态;超载工况下,梁体底板逐渐消压,跨中附近接缝截面底板开裂,随后裂缝逐渐变宽并竖直向上延伸,直至荷载超过接缝截面抗力设计值后,顶板局部混凝土压碎,而钢绞线未屈服;体外预应力节段预制胶拼梁具有较大的抗弯极限承载能力,可能发生的破坏模式为跨中附近接缝截面顶板混凝土受压破坏。

Model Tests for Ultimate Bending-Resistant Capacity of Prestressed Beam with External Prestressing Tendons and Glued Joints

To study the ultimate bending-resistant capacity and failure mode of precast beam with external prestressing tendons and glued joints,a continuous box beam bridge with continuous units of 3×30 mwas taken as the example bridge for the study,with the focus on the central span that is under unfavorable loading condition.Based on the similarity theory,a 10 m-long simplysupported I beam was made at a scale-down ratio of 1∶3,to which stepped load-applying tests were performed in two stages,including the loading combination of maximum positive bending moment in midspan when the beam reaching the design ultimate load bearing capacity and the loading condition of oversized live loads.The results demonstrate that the strength and stiffness of the beam can meet the design requirements under the loading condition of maximum midspan positive bending moment,and the structure is generally compressed and in the elastic load-carrying state.Under the loading condition of oversized live loads,the compression in the base slab of the beam showed the sign of gradual diminishing,and cracking was observed in the base slab at the locations of joints near the midspan,with cracks consistently widening and vertically propagating upward,till the time that the loads applied surpassed the design value of the joint cross-section resistant force,local part of the concrete in the top slab were crushed,but the steel strands did not yield.The precast beam with external prestressing tendons and glued joints has great ultimate bending resistant capacity and is supposed to experience the failure mode of compressive damage of top slab concrete at the locations of joints near the midspan.