钢管混凝土拱极限承载力计算及相关参数分析

Computation of Ultimate Bearing Capacity Load for Concrete Filled Steel Tube(CFST) Arch Bridge and Analysis of the Relevant Factor

采用考虑材料非线性的钢管混凝土拱极限承载力计算方法,对两个模型拱进行了极限承载力计算及相关参数分析.在该方法中,对钢管混凝土拱结构采用纤维单元模型,该模型假定钢管与混凝土完全粘接,钢管对核心混凝土的套箍作用体现在以一维形式表达的核心混凝土的应力-应变关系曲线之中.针对材料非线性分析中单元内各点刚度参差不齐的特点,采用单元内设小元的方法(相当于子结构),编制了非线性有限元程序.在该程序中,计算模型完全是基于小元层次进行的,比如:单元刚度矩阵由小元刚度矩阵凝聚而成,单元节点的残余力由小元节点的残余力构成,故只需改变单元内小元个数这一个参数,就可实现对结构的重新划分,极大地降低了非线性方程组的阶数,且方便实用.在程序计算结果得到模型试验结果验证的基础上,还分析了套箍系数、截面含筋率及混凝土强度对结构极限承载力的影响.

The ultimate bearing capacity load of two concrete filled steel tube(CFST) models is calculated,where the non-linearity has been considered.This means concrete filled steel tube arch model was simulated by fibre element and based on this presumption,steel tube and concrete are binded and the restriction of steel tube within the concrete is included in stress-strain relation.The structure is divided into sub-element which can reflects the change of stiffness along the length of element exactly.Two programs are compiled,one program treats the ultimate bearing capacity load of CFST in plane considering geometrical and structural non-linearity and the other program treats the ultimate bearing capacity load of CFST in space considering non-linearity. In the latter program,calculating model is based on sub-element,where the element stiffness matrix is made up of the sub-element stiffness matrix and the remaining force of node in element consists of the remaining force of node in sub-element.It is a method in which the structure is divided into NELEM element and every element is divided into ND sub-element,despite the influence of geometry factor,and its calculating precision is equal to other method in which the structur is divided into NELEM×ND element.The results from the old element are compared with the experimental data and it shows the programming procedure is correct.Based on the above, the influence of parameter such as restriction coefficient and the intensity of concrete on the ultimate bearing capacity load has been analysed and it provides references for engineers.