Y特大桥桥面系病因及加固方案受力性能研究

【作者】 陈清华；

【导师】 张晔芝；

【作者基本信息】 中南大学 ， 土木工程， 2011， 硕士

【摘要】 y特大桥为76m+360m+76m三跨连续自锚中承式钢管混凝土拱桥,桥面结构由混凝土桥面板、钢小纵梁和钢横梁组成,混凝土桥面板与钢横梁相结合。该桥运营仅十年,桥面系钢纵、横梁连接处就出现严重病害。本文采用有限单元法对该桥桥面系钢纵、横梁连接处病因、桥面系加固方案和加固过程中桥面系的受力状态进行了研究,主要完成了以下工作：1.用M工DAS软件建立全桥及3个节间局部有限元模型,对原桥面系受力性能进行了研究,得出结论：该桥超载现象十分严重,钢纵横梁连接角钢、与钢纵梁相连的横梁腹板,超载下应力过大,发生疲劳破坏；钢横梁腹板在部分加劲肋下缘处有应力集中现象,造成开裂。2.对两个加固方案进行了对比研究。两个加固方案都增设了大纵梁、增强了钢横梁,并对钢纵、横梁采用新的连接,提高了桥面系的刚度、整体性和运营安全系数,桥面系钢结构应力得到大幅度下降,即使在超载下疲劳应力幅也在规范容许值内,两个加固方案原则上都是可行的。3.加固方案一中钢纵、横梁的连接更换为“悬挂式、横梁腹板与钢纵梁上翼缘用铰接螺栓连接,其它部位不连接”；方案二中“钢纵、横梁只在下翼缘用普通螺栓连接,其它部位不连接”。二者连接部位超载下的最大疲劳应力幅分别为70.6MPa.29.4MPa,方案二受力更为合理,为推荐方案。4.对加固过程中桥面系的受力状态进行了研究。加固过程中,钢横梁腹板和下翼缘开孔后钢横梁不会全断面屈服；建议先将钢横梁下翼缘与腹板焊缝裂缝处理后再在钢横梁上开孔；换吊索过程中,桥面系钢构件和邻索的最大应力均小于屈服强度；大纵梁安装顺序对桥面线形及吊杆受力无太大影响,可结合现场施工条件进行安排。本文的研究成果为Y特大桥加固设计、施工提供了依据,对其它类似结构也有参考价值。更多还原

【Abstract】 Y is a self-anchored, semi-supported concrete-filled steel tube (CFST) arch bridge with three-span of 76m+360m+76m. The bridge’s floor system consists of concrete slab, little steel stringer and steel beam, and concrete slab combined with steel beam. Serious diseases have found in the connection between little steel stringer and steel beam, just after a decade’s operations. With finite element method, floor system disease cause, plan of reinforcement and floor system’s mechanical behaviors in the process of Strengthening were analyzed in this paper. The maioj tasks are summrized as follows:1. The space finite element model of the full bridge and three segments local finite element model of the floor system were established by using Midas. By studying original floor system’s mechanical behaviors, comes to the reason of the disease:due to the very severe overloading in Yajisha bridge, the stress of connection angle which connect little steel stringer with steel beam, steel beam web which connected with little steel stringer is too large, leading to fatigue damage. Steel beams at the edge of some stiffening ribs have stress concentration, resulting in cracking.2. The two plans of reinforcement are studied. Through adding large steel stringer, strengthening steel beams and making little steel stringer and steel beam have another kind of connection, it raise floor system integrity and improve the safety factor of the bridge operation, and the stress of floor system is much more less than before, fatigue stress amplitude are within the allowable value even under overload. The results showed that the two plans of reinforcement are feasible in principle.3. The connection of little steel stringer and steel change to "Hanging, connecting steel beam web with steel stringer top flange by a hinged bolts, other parts are not connected" in reinforcement planⅠ, "connecting steel beam bottom flange with steel stringer bottom flange by a ordinary bolts, other parts are not connected" in reinforcement planⅡ. The connection’s Maximum fatigue stress of plan I is 70.6MPa, planⅡis 29.4MPa. The plan II is more reasonable than plan I, so plan II being recommended at last.4. Floor system’s mechanical behaviors in the process of Strengthening were analyzed. Steel beam will not be full section yield after drilling holes in it’s web and bottom flange. The suggestion is that dealing with crack before drilling holes. In the process of change sling, floor system and adjacent cable’s maximum stress is less than the yield strength. The sequence of large steel stringer installation has no great impact on deformation and stress state, so the sequence can be choose according to on-site construction conditions.The research results of this paper have applied to the reinforcement design and construction control of Yajisha bridge. Meanwhile, it can be as a reference for others same type bridges.更多还原