柔性立管内部骨架层径向承载能力计算研究

Calculation of Radial Bearing Capacity of Internal Carcass Layer of Flexible Riser

骨架层作为非粘接柔性立管的最内层结构,其主要失效形式是径向压溃。为了探讨骨架层的径向承载能力,以铁木辛柯弹性稳定理论为基础,通过模型简化及刚度等效方法,建立了非粘接柔性立管骨架层的理论模型,求得其在静水压力作用下的临界压溃值。针对理论模型无法计入层间接触、材料非线性及初始椭圆度等因素,利用ABAQUS建立骨架层的三维有限元数值模型,分析了骨架层的材料非线性和初始椭圆度对骨架层径向失效的影响。分析结果表明:材料非线性会较大幅度地降低骨架层的临界压溃值;随着初始椭圆度的增大,骨架层临界压溃值减小。利用多层厚壁圆筒模型计算出骨架层在不同初始椭圆度下,考虑材料非线性柔性立管所能下放铺设的适用水深,实现了其工程应用。所得结果可为柔性立管的安全使用提供参考。

The carcass layer is the innermost layer structure of the un-bonded flexible riser.Its main failure mode is radial crushing due to excessive external pressure.Based on the theory of elastic stability of Timoshenko,the theoretical model of the un-bonded flexible riser carcass layer is established by model simplification and stiffness equivalent method.The critical crushing value under hydrostatic pressure is obtained.For the factors such as interlayer contact,material nonlinearity and initial ellipticity that cannot be included in the theoretical model,the three-dimensional finite element numerical model of the carcass layer is established by ABAQUS to analyze effects of the material nonlinearity and initial ellipticity of the carcass layer on the radical failure of the carcass layer.The analysis results show that the material nonlinearity will greatly reduce the critical crushing value of the carcass layer.With the increase of the initial ellipticity,the critical crushing value of the carcass layer decrease.The multi-layer thick-walled cylinder model is used to calculate the operation water depth of the flexible riser carcass layer under different initial ellipticities and considering the material nonlinearity.Its engineering application is realized.