京津冀生态环境建设：现状、问题与应对

以一座钢管混凝土连续梁拱组合单线铁路桥为工程背景，采用先整体后局部的两步分析法，首先利用Midas/Civil软件建立全桥有限元模型，计算拱肋安装及后续施工阶段结构的受力状态，得到局部模型的力边界条件；然后利用ANSYS软件建立拱脚结点局部有限元模型，分析施工期间拱脚结点的局部应力分布规律和应力集中程度；最后将拱脚结点应力计算值与实测值进行比较。结果表明，拱肋与梁体间传力顺畅，拱脚混凝土基本处于受压状态；拱脚内侧与箱梁顶板交界处应力集中现象较明显；拱脚上部拱肋周围、拱脚前脚趾处及两拱脚之间箱梁顶板的局部区域出现较大的拉应力，建议在同类桥梁的设计中加强这些部位的构造措施和配筋。拱脚结点应力计算值与实测值比较接近，说明用实体有限元模型计算的局部应力是可靠的，可用于设计验算。

Monitoring and Analysis of Springing Stress for Continuous Composite Bridge of CFST Arch and Tied Girders Under During Construction

Based on a continuous composite bridge of concrete filled steel tube(CFST) arch and tied girder on single track railway, using two step method of first whole and local analysis, the finite element(FE) model of whole bridge is built by Midas/Civil. The internal forces at the border of local FE model are calculated in arch installation and subsequent construction stages. Secondly, local FE model of springing joint is developed by ANSYS, and the distribution and stress concentration of local stresses are analyzed during construction. Finally, the calculated stresses of springing joint are compared with measured stresses. The results indicate that forces transfer smoothly between arch rib and girder, the concrete in springing joint is in compression condition mainly; distinct stress concentration occurs in the junction between the inside of springing and top deck of box girder; large tensile stresses appears around arch rib at top of springing, in front toe of springing, and top deck between two adjacent springings. It is advised that structural measures and reinforcement design of these parts should be strengthened in the design of similar bridges. Calculated stresses of springing are close to measured values, which shows local stress calculated by solid finite element model is reliable and can be used in the design checking.