薄壁箱梁大吨位预压力锚固区局部承压

随着连续刚构梁桥跨度越来越大,悬臂施工中大吨位预压力锚固的应用也越来越普遍,但是大吨位预应力锚固区薄壁混凝土箱梁承压局部应力分布复杂,通过对大吨位锚下混凝土局部应力分析,揭示其分布规律是后张法预应力混凝土桥梁结构有待解决的课题之一.从理论上对局压问题的影响因素、破坏原因及局压产生的裂纹类型等进行了阐述.结合重庆菜园坝长江大桥北引桥连续刚构混凝土梁桥工程实例,一方面,根据现行的《公桥规》中有关局部承压强度、抗裂性及最小保护层厚度等方面的规定,对0块顶板T2大吨位预应力束(设计值拉力4 882.5 kN)下混凝土进行了验算,另一方面通过有限元仿真分析,两者所得的结果相互验证,均符合规范规定要求.结论指出采用在锚下混凝土中增设横向拉筋使之与腹板内两侧钢筋网片形成封闭箍筋的设计可以解决大吨位薄壁腹板混凝土局压问题.

Partial Pressure Problem About Continuous Rigid Frame Bridge Anchorage Zone of Thin Concrete Box Girder Webs Carrying Large Tonnage

With continuous rigid frame bridge span increasing,cantilever construction of large tonnage anchor are also becoming more common,but local stress distribution is complicated on prestressed anchorage zone of thin concrete box girder webs by the large tonnage,which reveals its distribution of post-tensioned concrete bridge structure to be solved in the future.Based on the theory,some key points such as pressure factors,destruction and the reasons for the compression type crack were discussed in the paper.By using the North Approach continuous rigid frame concrete bridge of Yangtze River Bridge project example,the local compression strength,crack resistance and the smallest protective layer thickness of the first segment of one continuous rigid frame box girder bridge under design value Rally 4882.5 kN of No.T2 tendom,according to the local pressure formulas of Code for Design of Highway Reinforced Concrete and Pre-stressed Concrete Bridges and Culverts of China(JTG D62-2004) and Finite Element Method,were checking.Both the results verify that meets the standard requirements.The results reveal that the design of a web-Laced with horizontal steel mesh sealed off side stirrup can solve the partial pressure problem.