基于统计过程控制理论的张力腿平台有效上浪波高分析

文章以统计过程控制理论(Statistical Process Control,SPC)为基础提出了一种张力腿平台甲板有效上浪高度计算模型,针对海浪波高是随机过程这一不确定因素导致的上浪波高没有确定解的情况,分析计算了波浪谱下的张力腿平台相对运动和有效上浪波高,计算得到了有效上浪波高控制中心均值、下管制限值、上管制限值和相应发生概率。由相同波浪参数下不同波浪谱计算得到的有效上浪波高控制中心均值相同这一结论,发现波浪能量在不同谱之间的分布是相同的,说明波浪能量在时间维度、空间维度和频率维度的分布是一致的。在求解有效上浪波高控制中心均值时,提出了能更好刻画波高在波浪参数下的分布形式的面积均值法,并由此方法计算控制中心均值和上管制限值。以一型张力腿平台为例,针对波浪谱中超过某一发生概率的情况,运用统计过程控制理论和SPC控制图,计算了有效上浪波高控制中心均值、下管制限值和上管制限值,判断随机有效上浪波高是否处于统计控制状态,发现了波浪谱中的发生概率越大,随机有效上浪波高越可控这一规律。比较不同波浪入射角的有效上浪波高控制中心均值,发现了不同波浪入射角对有效上浪波高影响不大、发生概率对有效上浪波高影响较大的规律。最后基于统计过程控制理论计算得到整个有效上浪波高均值、发生概率、下管制限值和上管制限值。提出了在有效上浪波高均值和上管制限值之间结构物会受到交变载荷的作用容易疲劳损伤和腐蚀损伤的建议。结果表明该方法可以对张力腿平台有效上浪波高进行计算,并可推广应用于其它海上结构物的有效上浪波高计算。

Analysis of Effective Height of Green Water Loading for Tension Leg Platform Based on Statistical Process Control

A calculation model is established to research on effective height of green water loading of Tension Leg Platform (TLP) based on statistical process control theory. The relative motion and ef-fective height of green water with wave spectra as parameter for TLP are analysed, and the center lines, upper control limits and exceeding probability about effective height of green water are calcu-lated. The mean area method, which fits well with wave height distribution form, is presented to cal-culate center lines and upper control limits of effective height of green water. It is found that the wave energy distribution between different wavespectra is the same, because the center lines of effec-tive height of green water of different wave spectra with the same wave parameters are the same. It is evident that the wave energy distribution is accordant in time dimension, spatial dimension and fre-quency dimension. A TLP example shows that it is much easier to arrive at in control state for the condition that effective height of green water with great exceeding probability in wave spectrum. It is a given rule that the influence of wave incident angle on effective height of green water is little by compared with the center lines of effective height of green water with different wave incident angle. Results show that this method is a powerful and simplified methodology with quite less calculation time to support fast estimating effective height of green water. This method can also be applied to other marine structures to calculate effective height of green water.