为有效改善钢-混凝土连续组合桁梁桥负弯矩区受力性能,以天津海河吉兆桥为例,总结连续组合桁梁桥的主要设计难点,并对传统的解决方案进行评述,在此基础上提出综合采用部分组合技术、双重组合技术以及优化施工工序3项措施对吉兆桥进行优化设计.采用MIDASCivil软件建立吉兆桥边上1榀组合桁架有限元模型,进行施工全过程分析,检验3项优化措施的有效性.对比分析结果表明,采用此3项技术措施可使混凝土桥面板在荷载短期效应组合下始终受压,下弦杆钢板最大压应力相比不灌混凝土方案降低了约25％.可见,合理采用此3项技术措施可显著降低钢-混凝土连续桁梁桥负弯矩区混凝土桥面板的拉应力和下弦杆钢板的压应力,从而有效避免混凝土桥面板开裂,改善下弦杆的稳定性.%To effectively improve the mechanical behavior of the hogging moment area of the steel and concrete continuous composite truss girder bridge, the Jizhao Bridge over Haihe Rive in Tianjin was cited as an example. The major design difficulties of the composite truss girder bridge were summarized and the conventional solutions to the difficulties were commented. Based on the summarization and comments, three measures of the partial composite technique, double composite techniques and optimized construction sequences were proposed for the optimal design of the Jizhao Bridge. The software MIDAS Civil was used to set up the finite element model for a side composite truss of the bridge, the whole construction process of the bridge was analyzed and the effectiveness of the three measures was checked. The results of comparative analysis reveal that the application of the three measures can keep the concrete deck slabs in compression all the time under the short-term combination of load effect and can make the maximum compressive stress in the steel plates of the lower chord reduced by about 25% as compared to the design scheme that the concrete is not cast. It is known herewith that the rational application of the measures can significantly reduce the tensile stress in the deck slabs and the compressive stress in the steel plates of the lower chord in the hogging moment area of the bridge, therefore can effectively avoid cracking in the slabs and improve the stability of the lower chord.
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