液化侧扩流场地高桩码头地震反应特性与全局敏感性分析

The liquefaction-induced lateral spreading is main cause of damage to the pile-supported wharf (PSW), which is a commonly used port engineering structure, during earthquake. However, there is a lack of in-depth research on the effects of the liquefaction-induced lateral spreading on the PSW. Therefore, in line with the "step by step" principle, the project will fully explore the seismic response characteristics of the PSW subjected to the liquefaction-induced lateral spreading as well as the main factors, aiming at gaining insight into the earthquake damage mechanism and developing seismic technologies. Firstly, three-dimensional modeling technique is utilized to investigate the seismic response of the PSW in liquefaction-induced lateral spreading ground considering the soil-pile-structure-crane interaction. The feasibility of the used modeling technique is validated through the multi-structural segment model under typical earthquake event. Secondly, the combination of repeated numerical simulations and earthquake event analysis is adopted to further explore the seismic response of the PSW and the relationship among them, which allows for shedding light on the seismic response characteristics. Finally, a polynomial chaos expansion (PCE) surrogate model, which is constructed from a small set of training data, is employed to characterize the input-output relationship of the PSW. Within the PCE surrogate model, the global sensitivity analysis can be analytically implemented and then used to efficiently determine the main factors of seismic response of the PSW. This project has a great theoretical significance and application value for accelerating the research on seismic response of the PSW subjected to the liquefaction-induced lateral spreading and development of the effective seismic technologies.

高桩码头应用广泛，场地液化侧扩流是导致高桩码头震害的主要原因，但是对这一重要的港工抗震问题一直缺乏深入研究。鉴于此，本着“循序渐进”原则，本项目系统研究液化侧扩流场地高桩码头地震反应特性与主要影响因素，为后续逐步开展震害机理、抗震技术等研究奠定基础。首先，针对液化侧扩流场地桩－土－结构－起重机相互作用体系，研究地震反应分析三维数值建模途径，并基于典型震害实例建立多结构段数值分析模型，验证建模途径的可靠性；然后，通过反复数值模拟与震害实例分析相结合手段，认识高桩码头地震反应及各反应量间的关系，进而研究液化侧扩流场地高桩码头地震反应特性；最后，根据地震反应的少量训练样本，建立表征输入输出关系的多项式混沌展开模型，以实现解析的全局敏感性分析，用于确定液化侧扩流场地高桩码头地震反应主要影响因素。本项目实施，对于加快推进液化侧扩流场地高桩码头地震反应与抗震技术研究，具有重要的理论意义与应用价值。

项目针对港口工程中高桩码头抗震问题，系统开展了液化侧扩流场地高桩码头地震反应特性和主要影响因素分析。首先，详细给出起重机―高桩码头体系数值建模途径；接着，系统分析液化侧扩流场地高桩码头地震反应特性；最后，采用全局敏感性分析方法，全面评价输入参数对高桩码头关键响应量的影响。.针对起重机―高桩码头数值模拟，模拟方法如下：(1)起重机杆件采用弹性梁－柱单元模拟，杆件之间的连接假定为刚性连接，起重机的重量和质量通过单元节点施加；(2)根据不同的数值模型，确定相应的计算区域；(3)桩基采用纤维截面的非线性梁－柱单元模拟，桩－土相互作用采用零长度单元模拟；(4)给出考虑桩基预应力的高桩码头并行数值计算步序；(5)建立有/无起重机高桩码头数值模型。针对高桩码头地震反应特性，可知：(1)混凝土抗压强度与钢筋屈服强度对高桩码头结构的地震响应影响较大；(2)水泥土加固措施对码头体系地震响应减弱最明显，其次是销桩加固措施，最后是刚板桩加固措施；(3)在地震作用下，起重机的动力行为对下部码头结构的动力响应影响较大。针对全局敏感性分析，表明：(1)土层的渗透系数对高桩码头结构体系的易损性影响不明显。(2)不考虑起重机时，桩的最大位移、弯矩和曲率受最软土层的摩擦角影响最明显，各输入参数之间的交互作用不明显；(3)考虑起重机时，在变异系数较大时，各输入参数之间的交互作用较明显；(4)当考虑起重机后，各输入参数对各关键响应量影响有不同程度的变化，各输入参数的交互作用在变异系数为5%时无明显差别，在变异系数为30%时均增大。.项目执行过程中，发表学术论文17篇，授权发明专利4项、实用新型3项、软件著作权2项。项目创造性解决了强震下液化侧扩流场地起重机―高桩码头耦合分析方法，并用采用高斯过程替代模型完成了起重机―高桩码头体系全局敏感性分析。项目研究成果对于加快推进液化侧扩流场地高桩码头抗震技术研究，具有重要的理论意义与应用价值。