大跨径简支转连续箱梁桥收缩徐变效应

Shrinkage and creep effects of long-span simple-supported-to-continuous box girder bridge

利用杆系有限元模型计算了大跨径简支转连续箱梁预制和施工过程中的应力分布和线形变化,研究了预应力束二次张拉对收缩徐变的作用。以6×70m连续箱梁为例,按照老化理论原始算法、老化理论修正算法、JTJ023—85规范附录算法与JTG D62—2004规范附录算法,进行了收缩徐变效应对简支状态和连续状态下箱梁结构应力和变形影响的对比分析。分析结果表明:不同算法的收缩徐变效应对各跨跨中或支点应力影响的最大差值均在15%以内,对边跨、次边跨、中跨跨中挠度影响的最大差值分别为36%、79%、54%,其中JTJ023—85规范附录算法计算的挠度最小,JTGD62—2004规范附录算法计算的挠度最大,也最接近实测挠度,因此,收缩徐变理论的计算分析结果可靠。

The stress distributions and deformations of long-span simple-supported-to-continuous box girder bridge during different construction stages were calculated by bar finite element models. The influence of prestressed bar＇s second-time stretching on shrinkage and creep effects was studied. Taking the 6×70 m continuous box girder bridge as an example, according to different types of calculating methods, including the original algorithm of aging theory, the modified algorithm of aging theory, the algorithm in the annex of JTJ 023—85 Code and the algorithm in the annex of JTG D62—2004 Code, the influences of shrinkage and creep effects on the stresses and deformations of box girders during simple-supported stage and continuous stage were compared. Computational result shows that the maximum influencing discrepancies of stresses at mid spans and supporting points are within 15%, and the maximum influencing discrepancies of deflections at the mid-sections of end span, side span and midspan are separately 36%, 79% and 54%. The deflection calculated by the algorithm in the annex of JTJ 023—85 Code is smallest, while that calculated by the algorithm in the annex of JTG D62—2004 Code is biggest and also is closest to the actual measured value. It＇s confirmed that the theoretic analysis of shrinkage and creep effects is reliable. 1 tab, 8 figs, 10 refs.