连续刚构桥设计关键技术问题的探讨

针对连续刚构桥箱梁混凝土开裂、跨中下挠、底板崩裂等病害,分析其产生的原因,提出一些防止病害发生的对策措施,主要有:腹板斜裂缝可以通过增加梁高、设置腹板下弯钢束及加强竖向预应力有效性来改善;跨中下挠可通过增加顶板负弯矩钢束、采用塑料波纹管和真空辅助压浆工艺、控制钢束张拉龄期及设置后期备用钢束来改善;底板崩裂可通过合理控制结构的预应力度、选择合适的墩身刚度、优化钢束配置、优化梁高变化规律、合理选择底板厚度与波纹管间距及设置防崩钢筋等来改善.

Study of Key Technical Issues on Design of Continuous Rigid-Frame Bridge

For the problems like the concrete cracking, midspan deflection and bursting crack in the bottom slab of box girder of continuous rigid-frame bridge, the causes leading to the problems are analyzed and some measures against the problems are proposed. The measures as proposed are mainly as follows: the oblique crack in the web can be improved by increasing the depth of the girder, setting the draped strands in the web and enhancing the effectiveness of the vertical prestressing; the midspan deflection can be improved by adding the negative moment strands in the top slab, utilizing the plastic corrugated pipes and construction technology of vacuum grouting, controlling the tensioning of the strands and concrete age and setting the spared strands for later period usage and the bursting crack in the bottom slab can be improved by rationally controlling the prestressing degree of the structure, selecting the appropriate rigidity of pier shaft, optimizing the layout of the strands and variation law of the depth of the girder, rationally selecting the thickness of the bottom slab, the spacing between the corrugated pipes and setting the bursting crack resistant reinforcement.