体外预应力钢－混凝土组合梁在负弯矩作用下的稳定系数研究

摘要：对组合梁施加体外预应力，可有效提高截面的开裂弯矩。负弯矩作用下体外预应力组合梁的极限承载力受失稳控制，其侧扭失稳表现为与纯钢梁不同的畸变失稳模式。本文考虑钢梁初始几何缺陷影响和残余应力影响，对体外预应力组合梁进行了有限元非线性稳定分析，计算结果与试验实测值吻合。通过改变截面参数，对25组组合梁在初始几何缺陷、不同残余应力分布和不同综合力比下的承载力进行计算，给出了预应力组合梁的长细比计算公式，与我国现行钢结构规范钢柱稳定曲线进行了比较。研究表明：承受负弯矩作用的体外预应力组合梁可用文中提出的长细比做参数采用钢柱稳定曲线进行计算。

Study of Buckling Coefficient of Steel and Concrete Composite Beams with external tendons under Negative Bending

Abstract: In hogging moment regions, the cracking resistance of the beams can be effectively in creased on adding prestressing to the composite beams with external tendons,. The ultimate resistance of a composite beam prestressed with external tendon is governed by either distortional lateral buckling or local buckling, or an interactive mode composed of the two buckling which is sharply different from the lateral torsional buckling mode in a bare steel beam. Based on the proposed restrained torsional buckling model, inelastic finite element buckling analysis of composite beams in negative bending is investigated, considering the initial geometric imperfection and the residual stress patterns, and the FE results are found agree well with the test results. By varying cross-section parameters, 25 groups of composite beams under negative uniform bending with initial geometric imperfection and different patterns of residual stress in steel beams are studied by means of the FE method. The slenderness of the studied beam is defined and the calculated result is compared with the Chinese Codified steel column design curves. It is demonstrated that the Chinese Codified steel column design curves can be used in assessment of the buckling strength of composite beams with the slenderness defined.