内置劲性骨架的PC箱梁桥合龙段时变性能分析

Time-varying Performance Analysis of PC Box Girder Bridge with Inner Stiff Skeleton at Closure Section

为了给悬臂施工的大跨径PC箱梁桥截面设计验算和服役桥梁评价提供参考,针对悬臂施工混凝土桥梁合龙段施工时的内置劲性骨架施工方式,考虑骨架对截面刚度及截面面积产生的影响,将内置劲性骨架的梁段转换为混凝土材料;采用数值分析方法,对内置劲性骨架合龙段箱梁结构内力时变的影响进行分析,并按照子模型法分析了合龙段劲性骨架影响区的应力时变影响。结果表明:虽然采用内置劲性骨架进行桥梁结构合龙的成桥内力较优,但随服役运营时间的增长,内置劲性骨架吸收有效预应力现象逐渐突显,导致合龙段箱梁截面混凝土有效应力不足;骨架刚度越大,混凝土压应力储备越小,严重时会在桥梁运营过程中导致跨中下挠及开裂,此现象应引起设计和复核验算的重视。

In order to provide references for section design and in-service bridge evaluation, a long-span PC box girder bridge under cantilever construction was studied. Considering the impact of skeleton on stiffness and sectional area, inner stiff skeleton was transformed into concrete materials in cantilever construction with inner stiff skeleton at closure section. Numerical analysis method was used to analyze the time-varying effect of the structural internal force in the inner stiff skeleton closure section. And the time-varying effect of its stress was also analyzed according to the sub-model method. The results show that the applying of inner stiff skeleton for closure section of girder bridge can achieve better internal force in finished bridge state. In addition, the phenomenon that inner stiff skeleton absorbs effective prestressing becomes prominent along with the growth of the service time, which causes the lack of effective prestressing of girder bridge concrete section in closure section. The stronger the stiffness of skeleton leaves, the smaller the compressive stress of concrete reserves. In the most severe case, it may cause downwarping and crack of the mid-span of in-service bridge, which should be taken into account in design and check calculation.