Study on Optimum Ratio of Inner Cable and External Cable in Prestressed Concrete Bridges Stiffened with External Cable

1)进行了钢桁腹板预应力组合箱梁的抗弯试验，以明确其开裂强度、极限强度和破坏模式。2)将上述试验结果与有限元平面框架计算程序分析的结果进行了比较。3)在上述试验结果和参数分析的基础上，讨论了内索和外索的最佳比例。4)进行了长期变形试验。自重和预应力为持续荷载。对混凝土徐变和收缩引起的位移和应变进行了一年多的观测。5)对设置外索结构的时变应力进行了分析，并编制了计算程序。6)将长期变形试验结果与分析结果进行了比较。7)研究了考虑长期变形的设置外索结构的内索和外索的最佳比例。8)总结了1996~1997年两年的所有结果，并完成了报告。

1) Bending tests of prestressed composite box girder with steel trussed web were carried out to clarify cracking strength, ultimate strength and collapse mode.2) The above test results from elastic state to ultimate state of the girder were compared with theoretical ones analyzed by plane frame computer program of finite element method. Furthermore, parametric analysis was performed and the results were summarized.3) Based on the above test results and parametric analysis, the optimum ratio of inner cable and external cable was discussed.4) The long-term deformation test was measured. Own weight and prestressing force are the sustained load. Displacements and strains due to creep and shrinkage of concrete were measured more than one year.5) Time-dependent stress of the structures with external cable were analyzed and its computer program was Developed.6) The test results of long term deformation were compared with the analyzed results.7) The optimum ratio of inner cable and external cable in the structures with external cable considering the long-term deformation, was investigated.8) All results of two years from 1996 to 1997 were summarized and the repot was completed.