钢桁腹-混凝土组合梁桥空间受力性能及设计方法研究

Steel truss concrete composite beam bridge is a new type of composite bridge, with light weight, good permeability, the reasonable performance and so on. In this paper, the mechanical properties and design method of this bridge are taken as the research object. The reasonable structure form of steel truss concrete joint is developed, the force transfer mechanism of joint under multi-direction force state is studied, and then the model and design method of joint are proposed. Considering the shear lag effect of bridge deck under multi-support and the stress distribution under the action of shrinkage and creep, the equivalent mechanical analysis model of concrete bridge deck and the simple shrinkage creep analysis method are established. At the same time, the spatial mechanics model of steel truss composite beam bridge is deduced to study the torsion, distortion effect and spatial stability of the whole bridge. Considering the characteristics of cantilever construction in the practice, the force situations of bridge in the whole stage of construction are studied to reveal the basic mechanical behavior of such bridges. The change characteristics of the overall structural deformation in the limit state and the stress increment of the prestressed tendon are discussed, and the ultimate bearing capacity design method is given. Based on the above design theory and method research, the design parameters of the overall structure are optimized to propose a reasonable structure system for the design of such bridge.

钢桁腹-混凝土组合梁桥是一种较新型的组合结构桥梁，具有自重轻、施工便捷、通透性好、整体受力性能合理等优点。本课题以该类桥梁的力学性能和设计方法为研究对象，研发钢桁架混凝土合理节点构造，研究其在多向受力状态下的传力机理，提出节点力学分析模型和设计方法。考虑点支承约束下的桥面板剪力滞效应和收缩徐变作用下的应力分布规律，建立混凝土桥面板等效力学分析模型和简易的收缩徐变分析方法。同时，推导钢桁腹-混凝土组合梁桥的空间力学模型，研究其整体结构的扭转、畸变效应和空间稳定性能，考虑实际桥梁施工中采取的悬臂浇筑的特点，揭示该类桥梁的基本力学行为，探讨极限状态下结构整体变形和承载力设计方法。基于上述设计理论和方法的研究，对整体结构进行设计参数优化分析，研究其合理结构体系，为该种桥梁设计提供依据。

钢桁腹-混凝土组合梁桥是具有自重轻、施工便捷、通透性好、整体受力性能合理等优点。本项目以该类桥梁的空间力学性能和设计方法为研究对象，首先，研发了钢桁架混凝土合理节点构造，基于3组节点模型试验，对变形特征、滞回曲线、骨架曲线、延性系数及应力分布规律进行了对比分析，结果表明：新型开孔钢板节点的裂缝开展相对缓慢，主要分布在节点区域外，破坏时节点区域内混凝土保存较为完好，延性性能较好；新型开孔钢板节点屈服、极限、破坏荷载及位移均大于一般节点；在受压钢管中填充混凝土后，受压钢管的应力分布比较均匀。基于试验结果和数值模拟，推出了适合新型开孔节点的承载能力设计计算公式。考虑点支承约束下的桥面板剪力滞效应和应力分布规律，建立混凝土桥面板等效力学分析模型和简易的设计计算方法。.此外，分别进行2根试验梁模型的抗弯、抗剪荷载试验，观测试验模型裂缝发展情况及破坏形态，研究钢桁腹-混凝土组合梁基本抗弯、抗剪性能及偏载下的力学性能。试验结果表明：受弯试验梁裂缝集中在跨中3个节间，中间节间裂缝直接贯穿底板，整体呈现“灯笼”状。受剪试验梁裂缝分布总体上较均匀，且主要出现在底板外侧。在试验研究、数值模拟和理论分析的基础上，考虑上下节点区对抗弯刚度的影响，提出钢桁腹组合梁的简化力学模型，给出了挠度变形、承载力设计计算方法，为钢桁腹组合桥梁的概念设计和结构计算提供参考。