中文摘要：

利用超高性能混凝土（UHPC）的优越性能，提出了与之相适应的新型箱梁结构，主要目的是利用材料的高强度及新结构的轻型化，解决常规混凝土连续箱梁桥易开裂下挠、自重过大、跨径难以突破300m的难题。在原有工作的基础上，对主跨400m的UHPC连续箱梁桥进行了整体性能分析及优化设计，优化内容包括桥梁边跨长度、梁高、板厚等主要参数，以得到其合适的取值范围，根据优化结果建议：边跨与主跨跨径比范围为0.55~0.65；中支点梁高与主跨跨径比范围为1/20~1/25；跨中梁高与支点梁高比范围为1/1.8~1/2.3。整体性能分析结果表明，运用UHPC及新结构，能轻松实现连续梁桥400m跨径的突破，并具有较大的整体刚度及安全储备。综合考虑长期社会经济效益，在主跨跨径300~500m范围内，该新型结构可与斜拉桥、悬索桥等其它桥型形成强有力的竞争选型方案。

英文摘要：

By using the superior mechanical properties of ultra high performance concrete （UHPC）, a corresponding new box girder bridge structure is proposed, aiming at make use of the high strength of UHPC and the light weight of the new structure to solve the problems in conventional concrete continuous box girder bridges, such as easily cracking, large deflection, tremendous weight and limited span （under 300 m）. Based on the previous work, the overall performance analysis and optimization design to an UHPC continuous box girder bridge with 400 m main span are conducted. The optimized contents include the main parameters, such as the length of side span, the height of box girder, the plate thickness, etc. , so as to determine the proper range of the parameters. According to the optimization, the suggestion is made as follows： the ratio of side span to main span ranges from 0.55 to 0.65 ; the ratio of central fulcrum section height to main span ranges from 1/20 to 1/25 ; the ratio of mid-span section height to fulcrum section height ranges from 1/1.8 to 1/2.3. The result of the overall performance analysis indicates that by adopting UHPC and new structure, the breakthrough of main span over 400 m can be easily achieved in continuous girder bridge, and the new structure can also acquire larger overall stiffness and safety reserve. Considering the long-term social and economic benefits, when the main span ranges from 300 m to 500 m, the new structure would be a competitive scheme compared with cable-stayed bridge, suspension bridge, etc.