小跨高比混凝土简支箱梁静力性能试验研究

Experimental Analysis on Static Behaviors of Simple-supported Reinforced Concrete Box Girder with Small Depth-to-span Ratio

山地城市排水干管埋地箱涵由于滑坡导致地基塌陷而成为简支箱涵,支承方式的改变导致管道结构存在破坏风险。为此,文章对简支下小跨高比埋地箱梁进行了模型静力加载试验,分析了小跨高比埋地箱涵在简支条件下的破坏形式、抗剪性能以及剪力滞效应,讨论了现行有关设计规范对于箱涵抗剪承载力计算之不足。研究表明,竖向均布荷载作用下,小跨高比箱梁裂缝分布比较均匀,破坏时没有明显的临界斜裂缝,最终由于混凝土斜向受压柱压溃而丧失承载力。箍筋作为主要的抗剪部件,在斜裂缝出现后承担着大部分剪力。纵筋应变受内力重分布和裂缝发展等因素影响,部分区域呈现剪力滞效应。埋地箱涵由于滑坡地基塌陷导致的支承条件的改变将导致混凝土过早开裂,影响排水管道正常使用。

The buried box girders in the mountain city sewage pipeline system would be turned into simple- supported girders because of the removal of the foundation caused by landslide. This change of supporting would result in the failure risk of pipeline structure. The static properties of the buried box girders with small depth-to span ratio in simple supported condition are experimentally analyzed. The failure pattern, shear behavior and shear lag effect of the buried box girders in simple-supported condition are studied. The shortages in the present design codes for the calculation of shear capacities of the box girders are also discussed. It is shown that under the vertical uniformly distributed load, the crack distribution of the box girders is uniform, and no major critical diagonal crack is formed, and the box girders lose the bearing capacity in the form of concrete diagonal rod crushing. As the main shear bearing components, the stirrups devote much to shear capacity of the box girder after concrete cracking. The strains of the longitudinal rebars are affected by those factors such as the redistribution of internal force and cracks, so only few areas of the box girders show the shear lag effect. The change of supporting form leads to the premature cracking of concrete and affects the serviceability of the sewage pipeline.