【作者】 王长青；

【导师】 王树青； 李华军；

【作者基本信息】 中国海洋大学 ， 港口、海岸及近海工程， 2006， 硕士

【摘要】 大型土木工程结构(如海洋平台)在其服役期间,长期受到各种环境载荷作用,损伤不可避免。基于振动响应的大型结构无损检测技术对于确保海洋平台结构安全具有重大工程意义。本文主要通过模型试验验证发展出来的基于振动响应的大型结构无损检测技术,具体进行了以下工作。本文首先采用自然激励技术(NExT)和特征系统实现算法(ERA)研究了基于结构振动响应的模态参数问题。建立了海洋平台结构有限元模型,通过模态分析得到其理论模态参数;然后在外荷载的激励下得到其振动响应,利用特征系统实现(ERA)算法识别其值。结果对比表明自然激励技术(NExT)和特征系统实现算法(ERA)可以准确的识别结构模态参数。研究了基于模态应变能的结构损伤诊断算法,介绍了模态应变能变化率的诊伤指标。通过某海洋平台结构的数值算例验证了算法的有效性。算例中模拟了多种对角斜撑发生损伤以及有无甲板质量变化的损伤工况,数值结果显示仅需前两阶模态和每阶模态的水平自由度就可以进行损伤诊断,而且甲板的质量变化对于损伤定位几乎没有影响。本文在国家杰出青年科学基金“各类水工建筑物的动力分析(50325927)”,国家自然科学基金“环境荷载作用下海洋结构的模态参数识别与损伤诊断技术的研究(50479027)”的资助下,建造海洋平台物理模型,设置多种损伤工况进行振动台试验,利用前述特征系统实现(ERA)算法识别得到模态参数,最后利用模态应变能法进行损伤检测,验证了在环境激励下海洋平台结构的模态参数识别与损伤诊断方法的有效性。更多还原

【Abstract】 Large-scale civil engineering structures (for example, offshore platform structures) are prone to be damaged during their service lives, caused by various environmental loads. Therefore the occurrence of damage during the life of an offshore structure is unavoidable. Thus, techniques for nondestructive damage detection of large structures based on vibration response are essential to ensure safety. The developed nondestructive damage detection method based on vibration response in large-scale structures was validated by physical model test. And the thesis focuses on the following tasks.The first issue is to study the modal parameters based on vibration response utilizing the Natural Excitation Technique (NExT) and the Eigensystem Realization Algorithm (ERA). An offshore platform was modeled by Finite Element (FE) Method, of which the analytical modal parameters were obtained by modal analysis. Eigensystem Realization Algorithm (ERA) is applied to identify the modal parameters of the field testing under ambient excitation. According to the comparison results, the Natural Excitation Technique (NExT) and the Eigensystem Realization Algorithm (ERA) were shown to be effective for the structural modal parameters identification. The second issue is to study the damage detection method based on the modal strain energy, introducing the damage index of modal strain energy radio. Numerical example of an offshore platform was performed to prove the validity of this method.Several damage scenarios including damaged diagonal braces without and with the mass change of the deck of the structure are simulated. Numerical results indicate that this damage detection method can detect the diagonal damage(s) using the first two更多还原