基于刚度降低的大跨径预应力混凝土(PC)连续箱梁桥跨中挠度分析

Mid-span Deflection Analysis of the Long-span Prestressed Concrete Continuous Box-girder Bridge Based on the Stiffness Decreasing

为了研究大跨径预应力混凝土(PC)连续箱梁桥刚度降低对跨中挠度的影响。首先,通过一组小梁试验,总结了简支梁在集中力作用下的裂缝发展及分布规律;其次,建立了三个不同跨径的三跨连续箱梁桥有限元模型,采用跨中向两侧逐步降低单元刚度的方法模拟损伤,在集中力作用下跨中挠度呈现了"快速发展-缓慢增加-加速下挠"的变化规律。同时,计算了某实桥在预应力降低的条件下跨中挠度的变化情况;并提出了顶底板的预留预应力束张拉位置的建议。

In order to study the variation characteristics of the mid-span of long-span PC continuous box-girder bridges with the stiffness decreasing,firstly,a group of experimental beam tests were conducted and the crack laws of development and distribution rules under the concentrated forces for simply supported beams were summarized.In addition,three finite element models of continuous box girder bridges with different span length were developed.The reduction of the stiffness was gradually from the mid-span section to the supports. Undergoing the concentrated force,the deflections presented the trend of ＂ rapid development-slowly increasing-accelerative down warping ＂.Meantime,mid-span deflections of a finite element model of a real bridge under the prestressed tendons reducing were calculated. Optimized post tensioning positions have been suggested.