基于纤维单元的斜跨异型拱桥极限承载力分析

Whole Process Analysis on Ultimate Load-carrying Capacity of Skewed Special-shape Arch Bridge

斜跨异型拱桥拱肋同时受到面内和面外索力作用,为双向压弯构件,受力具有明显空间特征.采用梁单元纤维模型材料非线性方法,同时考虑几何非线性,对张家口通泰大桥进行极限承载能力全过程分析.随着荷载的不断增加,吊索逐根达到承载极限;拱肋同时发生面内、面外变形;一侧拱脚附近截面在轴力和面内、面外弯矩的共同作用下,逐步进入塑性;最后吊索全部屈服,主梁受力接近于简支梁,跨中截面形成塑性铰,全桥结构达到承载极限.纤维模型能够准确模拟拱肋双向压弯荷载下截面逐步进入塑性的全过程,适用于复杂受力构件梁单元材料非线性计算.

The rib of skewed special-shape arch bridge,under both in and out of plane cable force,is a biaxial bending and compression member,with obviously spatial characteristics.Using fiber element method,considering both material and geometrical nonlinearity,the whole process for ultimate load-carrying capacity of Zhangjiakou Tong-Tai Bridge was studied.With the load increasing,cables reached the limit load one by one;simultaneously,the arch rib deformed both in and out of plane;a cross section near one arch foot yield gradually,under the action of axial force and two-way bending load;finally,while the cables all yield,the main beam was closed to a simply supported beam,and came into being a plastic hinge in the middle section;the whole bridge reached load-carrying limit.Fiber model could accurately simulate a arch rib section under two-way compression bending load of the whole process step by step into the plastic,and applied to simulate material nonlinear beam member under complex force.