高速铁路桥梁大直径PHC管桩与承台连接力学性能试验研究

Experimental Study on Mechanical Property of Large⁃diameter PHC Pile and Cap Connection of High Speed Railway Bridge

为了研究铁路桥梁大直径高强度预应力混凝土管桩与承台的连接力学性能,依托新建沪苏铁路苏湖特大桥,对焊接钢筋和预埋套筒两种连接构造开展静力对比试验。采用现场足尺模型进行水平推力试验,加载方法为单向多循环法。通过试验得到荷载-位移曲线及节点混凝土和连接钢筋的应力-荷载曲线,分析其承载能力及力学性能。结果表明:在水平力产生的弯矩下,焊接钢筋法节点混凝土塑性发展迅速,结构应力增长快,连接钢筋受力不连续,未充分发挥受拉作用;预埋套筒法的节点局部变形量较小,节点混凝土塑性开展区域有限,结构延性较好,机械连接钢筋受力连续,连接钢筋在管桩与承台交界截面处受拉状态明显;焊接和机械锚固钢筋的最小长度建议值分别为30、20 cm(不含锚固长度)。综合比较,管桩与承台使用预埋套筒连接,承载能力更高,结构力学性能更优。

In order to study the mechanical property of the connection between large-diameter high-strength prestressed concrete pipe piles and caps of railway bridges,static comparative tests were carried out on the two connection structures of welded steel bars and embedded sleeves based on the newly built Suhu Bridge on the Shanghai-Suzhou Railway.The field full-scale model was used for horizontal thrust test,and the loading method was one-way multi cycle method.The load-displacement curve and the stress-load curve of joint concrete and connecting reinforcement were obtained through the test,and their bearing capacity and mechanical properties were analyzed.The results show that under the bending moment caused by the horizontal force,the plasticity of the joint concrete using the welded steel bars method develops rapidly,the structural stress increases rapidly,the connecting reinforcement is not continuously stressed,and the tensile effect is not fully exerted.The local deformation of the joint using the embedded sleeve method is small,the plastic development area of the joint concrete is limited,the structural ductility is good,the mechanical connection reinforcement is continuously stressed,and the connection reinforcement is obviously tensioned at the junction section between the pile and the cap.The recommended minimum length of welded and mechanically anchored reinforcement is 30 cm and 20 cm respectively(excluding anchorage length).Through comprehensive comparison,the pile and the cap are connected by embedded sleeve,which has higher bearing capacity and better structural mechanical performance.