复杂水力学条件下深水河道单壁钢围堰施工安全性:以清江河大桥1号承台钢围堰工程为例

Construction Safety of Single Wall Steel Cofferdams in Deep Water Rivers under Complex Hydraulic Conditions:Taking Qingjiang River Bridge No.1 Pile Cap Steel Cofferdam Project as an Example

目前针对单壁钢围堰施工过程荷载的取值,通常依靠现行规范中的线性荷载模式确定,无法真实反映受空间水力条件影响的围堰及承台施工受力情况。以清江河大桥单壁钢围堰工程为背景,综合考虑施工过程中围堰结构体系变化,提出了采用流体动力学与有限元相结合的改进荷载模式分析方法。将此方法与常规的基于现行规范荷载的有限元模拟方法进行对比,验证了该方法在复杂水力条件下对施工期单壁钢围堰结构受力安全的有效性。研究表明,在研究范围内,在混凝土受力方面,现有规范计算结果偏于不安全,其结果偏小约20%;而对于钢构件而言,位移结果比较接近,规范计算的环向次肋最大应力偏大约20%;利用大涡模拟(large eddy simulation,LES)湍流模型来模拟复杂河道水流条件,能够更好地反映空间复杂水流力对结构的影响。综上,研究成果有利于保障复杂水力条件下围堰结构施工安全,可为今后同类单壁钢围堰的设计和计算提供参考依据。

At present,the construction load value suffered by the single wall steel cofferdam is usually calculated by the linear load mode based on the current specifications,which cannot truly reflect the actual deformation and stress of the cofferdam and pile cap as a spatial structure during the construction period caused by the hydraulic characteristics.A single wall steel cofferdam in Qingjiang River Bridge was taken as a background project.By considering the change of cofferdam structural form during the construction process comprehensively,a new method with improved load model was established,which are combined by the fluid dynamics and finite element analysis.At the same time,compared with the hydrodynamic calculation method of the current specification,the reliability the structural safety of the new method were evaluated under the complex hydraulic conditions.It is shown that,within the research scope,in terms of concrete force,the existing code calculation results are biased to be unsafe,and their results are biased to be about 20%smaller.While for steel members,the displacement results are closer,and the maximum stress value of the annular secondary ribs calculated by the code is biased to be about 20%smaller.The use of large eddy simulation(LES)turbulence modeling to simulate the complex river flow conditions better reflects the effects of spatially complex water flow forces on the structure.In summary,the research results can be used to ensure the construction safety of the cofferdam structure under complex hydraulic conditions,and can provide a reference basis for the design and calculation of similar single-wall steel cofferdams in the future.