沅水大桥高桩承台钢吊箱围堰预制混凝土底板受力分析

Force Analysis of Reinforced Concrete Bottom Slab in Elevated Pile Foundation Steel Boxed Cofferdam in Yuanshui Bridge Project

通过对钢吊箱围堰的钢筋混凝土底模板的施工过程进行数值模拟,分析了混凝土底模板在自重荷载、安装钢围堰和施工封底混凝土3个施工步情况下其上应力和变形分布规律.高桩承台施工中采用钢吊箱围堰,利用钢筋混凝土底模板代替钢模板,对预制混凝土底模板的厚度和承受不同荷载之后的内力和变形分布规律进行分析,并进行了几何尺寸优化.分析中考虑板的自重,将钢吊箱重量作为分布荷载施加于板边预定位置,并在围堰内部预制板上施加封底混凝土重力荷载.分析结果表明:在自重荷载、钢围堰荷载和封底混凝土荷载作用下板中的应力和变形分布不均匀,板的厚度对板中的应力和变形影响显著.对于不等厚度底模板,其应力和变形亦能满足工程需要.依据应力分布特征对模板内部桩孔周围部分应力和变形的较大部位加厚,将传统等厚度模板变成不等厚度模板,既保证了施工过程的安全性,又减轻了结构自重,取得了较好经济效益,可为类似工程所借鉴.

The work progress of reinforced concrete slab was analyzed with finite element method before construction. The internal stress and deformation regularity of concrete slab were studied under three gravity loads of itself, steel boxed cofferdam, and bottoming concrete. The steel boxed cofferdam was adopted and the steel formwork was replaced by the reinforced concrete bottom plate in the construction process of high pile cap. The distribution law of the internal force and deformation under different loads and the thickness of precast concrete bottom formwork was analyzed and the geometric dimensions were optimized. The analysis process was divided into three steps. The plate weight was considered in the first step. The second step was to apply the weight of the steel hanging box to the edge of the plate as distributed load. Then the back cover concrete gravity load was applied on the internal precast slab in cofferdam. According to the analysis results, the stress and deformation distribution of the plate is uneven under the loads of plate weight, steel cofferdam and back cover concrete. The thickness of the plate has a significant effect on the stress and deformation of the plate. The stress and deformation of the template with different thickness can meet the engineering requirements. Therefore, it is necessary to maintain a larger thickness of the pile hole around. Based on the analysis result of internal stress and deformation, the slab was designed based on unequal thickness. The dead weight was reduced and the security of the project was assured. A good economic benefit has been obtained in this project and may be referenced by similar engineering.