大跨径简支转连续箱梁桥的线形观测与控制

采用杆系模型计算箱梁预制过程和施工过程中的应力分布和线形变化，分析了二次张拉的作用以及预应力管道参数、合龙时间、收缩徐变等对结构线形的影响。研究结果表明：二次张拉能有效地控制箱梁早期裂缝且对线形影响很小，而预应力管道参数、合龙时间、收缩徐变等对结构线形的影响不容忽略；在理论计算控制线形中，能否合理地选取计算参数是控制线形的关键。进而通过实测值和理论值的比较，验证了理论计算对线形控制指导作用的可靠性，为今后同类桥型施工控制提供了参考。

Line Shape Observation and Control of Simple-supported-to-continuous Long-span Box Girder Bridges

Using the finite element model of rod system, authors calculated the stress distribution and line shape during prefabrication and construction of box girder and analyzed the influences of secondary stretching and the effect of secondary stretching, prestress sheath parameter, closure time, shrinkage and creep on line shape of the structure. Results show that secondary stretching is able to control the incipient cracking of box girder and has little effect on the line shape, but the effects of sheath parameter, closure time, shrinkage and creep on line shape of the structure can not be ignored. So, in theoretical calculation of line shape control, whether line shape control is reasonable or not is determined by selection of parameters. Through comparison of test value and the theoretical value, authors confirmed reliability of the research which can provide the reference for line shape control of the long-span bridge in the future.