矩形管翼缘曲线组合梁弹塑性弯扭屈曲破坏机理研究

Curved steel and concrete composite girders with a rectangular tubular flange (RTFCGs) are an innovative composite structure with excellent mechanical and economic properties. RTFCGs have a risk of flexural-torsional buckling failure under external loads. However, few studies on the elasto-plastic flexural-torsional buckling, a complex mechanical behavior, of RTFCGs were carried out at present, and therefore it is still unclear for the elasto-plastic flexural-torsional buckling failure mechanism of RTFCGs. In this project, model tests, theoretical analysis and numerical simulation for RTFCGs are planned to be conducted, in order to systematically study its elasto-plastic flexural-torsional buckling failure mechanism. It is analyzed that the influence of the flexural-torsional coupling effect on the failure evolution process of RTFCGs with elasto-plastic flexural-torsional buckling, and whose failure criterion of elasto-plastic flexural-torsional buckling failure is proposed. The nonlinear stiffness matrix of RTFCGs with the elasto-plastic flexural-torsional buckling failure based on twin-shear unified strength theory is derived, and whose stiffness evolution model of the elasto-plastic flexural-torsional buckling failure considering the torsion-bending ratio effect is constructed. The total potential energy equation of the equivalent converted steel girder of RTFCGs with elastic flexural-torsional buckling is deduced,and the formulas of the critical strength of elastic flexural-torsional buckling and the strength of ultimate flexural-torsional buckling for RTFCGs are established. The research results of this project can supply the basis for perfecting the flexural-torsional buckling theoretical system of this innovative tubular flange composite structure with a high performance.

矩形管翼缘曲线组合梁是一种兼具良好力学性能与经济性能的新型组合结构。在外力荷载作用下，矩形管翼缘曲线组合梁存在弯扭屈曲破坏风险，但目前针对其弹塑性弯扭屈曲复杂力学行为的研究较少，其弹塑性弯扭屈曲破坏机理尚不明确。本项目拟采用模型试验、理论分析与数值模拟相结合的研究方法对矩形管翼缘曲线组合梁弹塑性弯扭屈曲破坏机理开展系统研究。分析弯扭耦合效应对矩形管翼缘曲线组合梁弹塑性弯扭屈曲破坏演化影响机制，提出其弹塑性弯扭屈曲破坏失效判别准则；推求基于双剪统一强度理论的矩形管翼缘曲线组合梁弹塑性弯扭屈曲破坏非线性刚度矩阵，构建考虑扭弯比影响的矩形管翼缘曲线组合梁弹塑性弯扭屈曲刚度演化模型；推导矩形管翼缘曲线组合梁等代钢梁弹性弯扭屈曲总势能方程，建立矩形管翼缘曲线组合梁弹性弯扭屈曲临界承载力和极限弯扭屈曲承载力计算公式。本项目研究成果可为完善新型管翼缘高性能组合结构弯扭屈曲破坏理论体系奠定基础。

矩形管翼缘组合梁在继承传统工字钢梁技术经济性能优势的基础上，极大改善了传统工字钢梁稳定性不足的缺陷，显著提高的弯扭屈曲强度使其尤其适用于弯扭耦合效应突出的曲线组合梁桥的建设需求。为揭示矩形管翼缘曲线组合梁弹塑性弯扭屈曲破坏机理，开展了具有不同曲率半径的5根矩形管翼缘曲线组合梁和2根工字钢梁弹塑性弯扭屈曲破坏试验，获得了弯扭耦合效应影响下试验梁弯扭屈曲破坏特征。分析了曲率半径对试验梁弹塑性弯扭屈曲承载力影响，表明了随着曲率的增大，试验梁弯扭屈曲承载力随之出现显著减小，同时证实了对比于相同曲率半径下工字形曲线钢梁，矩形管翼缘曲线组合梁承载力显著提高。建立了用于模拟矩形管翼缘曲线组合梁弹塑性弯扭屈曲行为的非线性数值分析模型，在此基础上分析了截面几何参数及内填混凝土强度变化对矩形管翼缘曲线组合梁弹塑性弯扭屈曲承载力的影响。. 基于试验及有限元分析结果，提出了矩形管翼缘曲线组合梁弹塑性弯扭屈曲破坏的初始屈服极限、初始失稳极限和强度极限3个失效极限状态及对应的判别准则，探究了不同曲率半径矩形管翼缘曲线组合梁弹塑性弯扭屈曲塑性演化特征。基于薄壁曲梁理论推导了矩形管翼缘曲线组合梁弯扭失稳的总势能方程。依据试验梁弹塑性弯扭屈曲破坏特征，推导了基于应力-应变协调关系的矩形管翼缘直线组合梁极限抗弯承载力计算公式。应用曲线梁弹性、非弹性稳定问题的统一公式，得出了矩形管翼缘曲线组合梁极限弯扭屈曲承载力计算公式。对比于试验结果表明，提出公式计算结果与试验值吻合良好，可用于矩形管翼缘曲线组合梁极限弯扭屈曲承载力计算分析。. 本项目解决了如何建立矩形管翼缘曲线组合梁弹塑性弯扭屈曲失效判别准则、塑性演化特征及承载力计算方法等问题，从而为矩形管翼缘曲线组合梁弹塑性弯扭屈曲性能的不断深入研究奠定了理论基础，也为管翼缘曲线组合梁桥高性能结构体系在我国的建设应用提供了技术支撑。