控制大跨连续刚构桥梁过度下挠的技术措施

Technical Measures for Control of Excessive Deflection of Girders of Long Span Continuous Rigid-Frame Bridges

为避免大跨连续刚构桥过度下挠及其危害,以主跨330m的重庆石板坡长江大桥复线桥为背景,研究有效控制该类桥梁过度下挠的技术措施。该桥通过采用钢-混组合结构体系降低恒载弯曲效应;通过设置体外索主动控制梁体的下挠;通过采取合理的预应力度和布置形式优化梁体受力;并结合应用恰当的徐变理论和参数以及通过加强混凝土养护等多种技术措施综合并用。通过与该桥多年实测的下挠数据及规律的对比,验证所采用技术措施的有效性。在此基础上对大跨连续刚构桥的设计提出了选择优良的结构体系、体外索主动控制下挠、优化预应力配置、保证工期及加强养护等有效的技术措施以避免梁体发生过度下挠的建议。

To avoid the excessive deflection of and its harm to the girders of long span continu‐ous rigid‐frame bridges ,the technical measures that could effectively control the excessive deflec‐tion of the girders of the bridges of the similar kind w ere researched on the Double‐Line Bridge of Shibanpo Changjiang River Bridge with a main span of 330 m in Chongqing .On the Double‐Line Bridge ,the steel and concrete hybrid structural system was used for the girder and the dead load flexural effect was thus reduced .The external prestressing cables were arranged and the deflection of the girder was actively controlled .The proper prestressing degrees and prestressing arrange‐ment were selected and the force conditions of the girder were optimized .Besides ,some more tech‐nical measures ,such as the proper concrete creep theory and parameters and the enhanced curing of the concrete ,w ere also comprehensively taken .T he contrast of the data and changing law s of the deflection of the bridge measured over years verified that all these measures worked well .Based on the research herewith ,the effective technical measures of selection of the better structural system , active control of the deflection ,using the external prestressing cables ,optimization of the pres‐tressing ,the assured construction time schedule and enhanced concrete curing were proposed for the design of the girders of long span continuous rigid‐frame bridges in order to avoid the excessive deflection .