钢桁拱桥非线性及面内极限承载力分析

以实桥为例,研究大跨度钢桁拱桥在面内荷载作用下的非线性结构行为,矢跨比、布载形式、温度荷载、钢材屈服强度对钢桁拱桥极限承载力的影响以及提高钢桁拱桥极限承载力的措施。结果表明:在活载半跨布载时,拱肋的破坏始于拱脚下弦的屈服,拱肋由无铰拱逐渐转化为三铰拱,最后由于拱脚塑性铰的破坏而导致拱肋失去承载能力;钢桁拱的工作过程可分为弹性段、位移稳定发展段及位移快速增长段,位移稳定发展段仍表现出弹性工作的特点;拱轴线的面内初始偏移控制在L/1000左右时,拱肋的极限承载力不会有明显降低;矢跨比越大承载能力越高;钢材屈服强度与钢桁拱极限承载力呈线性关系;温度的变化与承载力系数的变化大致呈线性关系;提高拱脚上、下弦杆处钢材的屈服强度和增大拱脚、L/4处截面的方式是提高钢桁拱桥极限承载的有效措施。

Analysis on the Nonlinear and In-Plane Ultimate Load Carrying Capacity of Steel Truss Arch Bridge

The nonlinear structure behavior of longspan steel truss arch bridge subjected to in-plane load is studied by an actual steel truss bridge.The effect of rise-span ratio,load form,temperature load and steel yield strength on the ultimate load carrying capacity of steel truss arch bridge is also discussed in this case,and measures for improving the ultimate load carrying capacity of steel truss arch bridge is put forward.Results show that the collapse of arch rib subjected to half-arch uniform vertical load begins from the yield at arch springing,the failure of load carrying capacity of arch rib results from the destruction of hinge at arch springing after the fixed arch is gradually transformed to three-pined arch.The working process of steel truss arch can be divided into elasticity phase,displacement stable development phase and displacement rapid development phase.Displacement stable development phase still exhibits the characteristics of elastic working.The load carrying capacity of arch rib is not decreased obviously as the in-plane initial deviation of the arch axis is controlled at about L/1 000.The load carrying capacity of the arch rib will increase as the rise-span ratio increases.Steel yield strength is linear with the load carrying capacity of steel truss arch.Approximately,temperature change is linear with the variety of the ultimate load carrying capacity coefficient too.Increasing steel yield strength in arch springing and quartered span is the effective measure for improving the ultimate load carrying capacity of steel truss arch bridge.