盖挖逆作地铁车站CFST柱-RC梁双暗牛腿节点抗剪性能研究

Study on the Shear Behavior of CFST Column-RC Beam Double Dark Bracket Joints in Top-Down Covered Excavation Metro Station

内蒙古呼和浩特轨道交通1号线大型换乘站新华广场站、2号线大学西街站及中山路站均采用盖挖逆作法施工。采用该种工法建造的地铁车站,钢管混凝土柱与车站楼板纵梁不能同期形成,二者后期连接对剪力高效、可靠的传递起关键作用。因此,梁柱节点设计时采用双梁—双暗牛腿的形式。但是,目前该种节点的抗剪性能、破坏形态和原理尚不明确,相关规范未给出明确的规定,亟待进一步研究。为此,文章采用室内试验针对该种节点的抗剪性能开展系统的研究。通过研究主要得到以下结论:下部环形牛腿承担的剪力始终大于上部环形牛腿,约为上部环形牛腿的2.4倍;裂缝贯通,梁发生剪切破坏,节点并未破坏,符合强节点弱构件的设计原则。

The large transfer station Xinhua Square Station of Line 1 and the University West Street Station and Zhongshan Road Station of Line 2,are using the method of top-down covered excavation in Inner Mongolia Hohhot rail transit.With this method,the concrete-filled steel tube column and the floor slab longeron of the station cannot be formed at the same time,and the late connection between them plays a key role in the efficient and reliable transmission of shear force.For this reason,the design of beam and column joints adopts the form of double beam and double dark cow leg.However,the shear resistance,the failure pattern and the principle of this kind of node are still unclear at present,and the relevant specifications have not given clear provisions,so it is urgent to further study.In this paper,the shear resistance of the joints is systematically studied by laboratory tests.Through the research,the following conclusions are drawn:The shear force undertaken by the lower annular leg is always larger than that of the upper annular leg,which is about 2.4 times larger;Fracture penetration,shear failure occurred in the beam,the node is not broken,in accordance wit h the design principle of strong nodes weak components.