桥用无粘结预应力混凝土T梁非线性有限元分析与试验研究

为研究桥用无粘结预应力混凝土梁的荷载-变形特性，用平面应力等参元建立了直线配索无粘结预应力混凝土T形截面简支梁的有限元模型，混凝土和钢筋分别采用了Ottosen屈服准则和Von-Mises屈服准则的弹性-完全塑性本构关系，无粘结预应力钢束简化为随加裁过程不断更新的外力边界条件；用弥散式裂缝模型模拟了混凝土的开裂并用Euler—Newton迭代法求解每个增量荷载步的有限元方程。用计算跨径为4200mm的简支试验梁进行两集中力三分点加载的试验对有限元模型进行验证，所建有限元模型可有效地分析出结构开裂和普通钢筋屈服等荷载-挠度曲线特征，与试验结果较为吻合．具有实用意义。

Nonlinear FEM Analysis and Experiment of T-shaped Prestressed Concrete Bridge Beam with Unbonded Tendons

In order to study the load-deflection characteristics of bridge prestressed concrete beams with unbonded tendons,a plane stress isoparametric element FEM model was established for a T-shaped prestressed concrete beam with straight-line unbonded tendons.Elastic-perfectly plastic constitutive models with the Ottosen's and the Von-Mises criterion were chosen for the concrete and the steel bar.Unbonded tendons were simplified as varying force boundary conditions while a smeared crack model was introduced to simulate the crack propagation.Nonlinear FEM equations were solved by the Euler-Newton iteration method.In order to verify the FEM model,a 4200mm span simply supported specimen was tested to failure by 2 concentrated loads locating at 1/3 span.The analytical load-deflection curve has shown excellent consistency with the experimental result,especially,the FEM model can figure out the characteristics of the load-deflection curve such as the 2 inflection-points representing the concrete crack and the yield of the rebar,which indicates that the proposed nonlinear FEM model is reasonable and practical.