风浪组合循环荷载下四桩导管架基础承载变形特性

Bearing-deformation characteristics of the tetrapod piled jacket foundation under combined wind and wave cyclic loading

关键词:  四桩导管架  海上风机  循环p-y曲线  风浪组合循环  承载变形特性

Key words:  tetrapod piled jacket foundation  offshore wind turbine  cyclic p-y curves  combined wind and wave cyclic loading  bearing-deformation characteristic

摘要:

为准确评估复杂环境荷载作用下海上风机四桩导管架基础的承载变形特性,本文基于改进非线性滞回圈p（桩侧土反力）-y（桩横向变形）曲线构建了基础的三维数值分析模型,并引入修正P乘子以考虑群桩效应和基桩轴力对基础水平承载特性的影响。同时,采用两点组合循环加载方式分别模拟风压与波浪荷载作用,并考虑其幅值、频率、作用高度等荷载特征差异。研究表明:当桩间距≥7D时,四桩导管架基础的群桩效应可以忽略,且随着加载高度的增加（加载位移控制不变）,基桩轴力对基础水平承载特性的影响逐渐增强；波浪占比的增加和风载高度的降低会显著增大基础变形及内力,且其对于风浪占比的变化更为敏感；小幅值组合循环作用下,桩顶位移随循环次数（取对数坐标）呈线性变化且累积位移趋于不变,但当加载幅值为0.4时,桩顶塑性累积位移持续增长。

Abstract:

To accurately evaluate the bearing and deformation characteristics of a four-pile jacket foundation under complex environmental loads, a three-dimensional numerical model was developed based on the improved nonlinear hysteretic p(soil resistance) -y (lateral displacement of the pile) curve, with P-multipliers incorporated to account for pile-group effects and axial forces. Furthermore, a two-point combined cyclic loading approach was adopted to represent wind and wave loads, respectively, taking into consideration differences in load amplitude, frequency, and application height. Results indicate that when the pile spacing is ≥7D, the group pile effect can be negligible, and as the loading height increases (constant loading displacement), the influence of axial forces on the foundation’s lateral behaviors is strengthened. An increase in the wave load ratio and a decrease in the wind load height significantly amplify the deformation and bending moment of the foundation, and it is more sensitive to variations in the load ratio. Under small-amplitude cyclic loading, the pile head displacement increases linearly with the cycle number (in logarithmic coordinates), and the cumulative displacement tends to stabilize. However, at a loading amplitude of 0.4, the plastic cumulative displacement continues to increase.