重复荷载下高铁24m箱梁模型试验研究

Experimental Research on the Static Performance of High-speed Railway Box Girder Model Under Repeated Loading

对高速铁路中广泛应用的预应力混凝土简支箱梁进行了多级重复荷载下的模型试验.试验的主要测试结果包括2种加载方式下梁的裂缝宽度和裂缝分布展开情况,荷载-挠度曲线和弯矩-转角曲线,混凝土和普通钢筋的应变分布等.研究结果表明:混凝土首先在跨中底板出现裂缝,然后慢慢向腹板扩展.在纯弯段,裂缝间距分布比较均匀.在施加荷载超过开裂荷载不多的情况下卸载,裂缝在预应力筋的作用下能够闭合.箱梁的最终破坏现象是混凝土顶板的压溃爆裂,跨中极限位移为跨径的1/55.重复加载下的荷载位移曲线的包络线有3个拐点,分别对应于混凝土开裂,钢筋屈服,预应力筋屈服;而重复荷载下的弯矩转角曲线在整个过程中有一个拐点,对应于预应力筋的屈服.

The simply supported prestressed concrete box model of widely applied high-speed railway girder under repeated loading is tested.Two cases,including larger loading space and smaller loading space are included in the three-point bending tests.The experiment is focus on the width and distribution of cracks,the load-deflection curve and moment-rotation curve,and strain distribution of concrete and steel.The test results show that the concrete cracks first appear in the bottom plate of the box girder,and then slowly extend to the web.In the area of pure bending,spacing distribution of cracks is relatively uniform.When the load is little bigger than the cracking load,cracks can be closed under the action of the prestressed tendons.The final damage phenomenon of box girder is crush and burst in the concrete roof plate and the ratio of limit displacement to span is about 1/55.Under the repeated loading,the envelope of load-displacement curve has three inflection points,respectively corresponding to the cracking of concrete,the yield of reinforcement,and the yield of prestressed strand wires;while the envelope of moment-rotation curve in the full range has one inflection point,corresponding to the yield of prestressed strand wire.