束合管幕结构结合缝受剪性能足尺试验研究

Full-scale experimental study on shear performance of joints of bundled integrate structure

为降低对城市地面道路、管线、建(构)筑物的影响,改善管幕法修建的地下通道结构受力,提出一种依托横向预应力的新型地下结构形式——U-BIT束合管幕工法。该工法采用矩形钢管,通过沿环向施加预应力,使各个钢管之间协同受力,形成受力整体,进而达到减小构件尺寸、提高结构的整体刚度和承载能力的效果。然而,U-BIT束合管幕结构的施工工艺以及结构性能的研究还处于初期阶段,其结构力学性能和受力薄弱点均不清晰,为保障该结构的施工安全,探究该束合管幕结构的性能以及拓展该结构的适用性,亟需对束合管幕结构的受力性能进行研究。本文在工程需求和前期文献调研的基础上,针对该束合管幕结构开展受剪性能的足尺试验,探究束合管幕结构在剪切作用下的变形响应,结果表明:预应力可有效增大结构抗剪刚度;结合缝薄弱位置出现在混凝土与钢管节的黏结界面处,无预应力作用时,主要由界面黏结作用及锁扣承担剪力,而锁扣抗剪承载仅在极限状态下发挥作用,设计时不宜考虑,建议仅考虑黏结作用;在结合缝张开以后,混凝土与钢管节有效黏结面积会显著减小,抗剪刚度随之降低,并引起结合缝错台的大幅增加,进一步引起抗剪承载力降低。

In order to reduce the impact on urban ground roads, pipelines, and buildings(structures), and to improve the stress of underground passage structure built by pipe curtain method, a new type of underground structure relying on transverse prestress, Underground Bundled Integrate Tunnel(U-BIT), was proposed. The construction method adopted rectangular steel tubes. By applying prestress along the circumferential direction,the coordinated force between the steel tubes was formed, thus achieving the effect of reducing the size of the members and improving the overall stiffness and bearing capacity of the structure. However, the research on the construction technology and structural performance of the U-BIT was still in the initial stage, and its structural mechanical properties and stress weak points were not clear. In order to ensure the construction safety, to explore the performance, and to expand the applicability of the bunched integrate structure, it was urgent to study the mechanical behavior of it. Based on the engineering requirements and previous literature research, full-scale experimental study on shear performance of the bundled integrate structure was carried out to explore the deformation response of the structure under shear action. The results are drawn. Prestress can effectively increase the shear stiffness of the structure. The weak position of the joint appears at the bonding interface between concrete and steel pipe joints. When there is no prestress, the shear force is mainly borne by the bonding interface and the lock. However, the shear load of the lock only plays a role in the limit state, so it should not be considered in the design stage. It is suggested to consider only the bonding effect. When the joint is opened, the effective bonding area between concrete and steel pipe will decrease significantly. The shear stiffness will decrease and the joint dislocation will increase greatly, which will further reduce the shear capacity.