成昆铁路矮塔斜拉桥索梁锚固区模型试验研究

为研究铁路矮塔斜拉桥索梁锚固区的受力形式,以成昆铁路金沙江大桥为工程背景,针对该桥采用的新型梁顶混凝土锚固构造,通过缩尺模型试验研究其在不同荷载下的应力分布和开裂特征。结果表明:在斜拉桥成桥恒载索力作用以及最不利荷载组合索力作用下,C7锚固块更容易发生破坏,将其作为试验构件开展缩尺模型试验,发现锚固块在不同张拉荷载作用下张拉至设计索力的过程中,应变增幅基本上线性增加,卸载后同样呈线性减小,说明混凝土受力处在线弹性阶段,且应力在规范要求范围内。在试验荷载加载至140%设计索力时,锚固块前端倒角位置开始出现细小裂纹且随荷载的增加不断开展。当荷载卸载至0时,之前出现的裂缝随荷载的减小逐渐闭合,宽度肉眼不可见,表明该构造能够满足正常使用要求且具备足够的安全储备。

Model Test on Cable Girder Anchorage Zone of Extradosed Cable-stayed Bridge on Chengdu-Kunming Railway

In order to study the stress form of cable girder anchorage zone of railway extradosed cable-stayed bridge,taking Jinsha River bridge of Chengdu-Kunming railway as the engineering background,aiming at the new girder top concrete anchorage structure adopted by the bridge,the stress distribution and cracking characteristics under different loads were studied by scale model test.The results show that under the dead load cable force and the most unfavorable load combination cable force of the cable-stayed bridge,the C7 anchor block is more likely to be damaged.Taking it as a model test component,the scale model test was carried out.It is found that the strain increase of the anchor block basically increases linearly in the process of tensioning to the design cable force under different tensioning loads,and also decreases linearly after unloading.It indicates that the concrete is stressed in the linear elastic stage,and the stress is within the range required by the specification.When the test load is loaded to 140%of the design cable force,small cracks begin to appear at the chamfer at the front end of the anchor block,and continue to develop with the increase of load.When the load is unloaded to 0,the previous cracks continue to close with the decrease of load,and the width is invisible to the naked eye,indicating that the structure can meet the requirements of normal use and has sufficient safety reserves.