穿刺工况自升式平台动力灾变特性

针对穿刺引起的自升式平台结构损伤问题，系统研究其动力灾变行为。考虑损伤积累对刚度衰减影响提出构件失效准则，在定义结构抗力和地基抗力基础上提出穿刺工况下平台结构失效准则，以121 m桁架式自升式平台为研究对象，考虑构件损伤演化及桩土动力耦合作用建立平台整体分析模型，并从入泥承载力、损伤影响、约束条件3方面验证了模型适用性；进一步基于整体失效准则开展穿刺工况下平台动力灾变演化模式研究。结果表明：构件损伤演化降低了平台极限承载能力并影响其整体灾变演化规律，CEL法可以有效模拟复杂土层桩土动力耦合作用；穿刺工况下平台失效模式受结构抗力和地基抗力共同影响，其演化规律为未穿刺桩腿与桩靴连接区域杆件由于船体倾斜产生较大弯矩发生塑性变形，随着穿刺深度的增加进一步演化为上下导向块区域桩腿杆件屈曲变形，这与穿刺工况下观察到的桩腿失效模式一致。

Dynamic catastrophic behavior of jack-up platform during punch-through

Aiming at the structural damage of jack-up platform caused by punch-through, a systematic study of dynamic catastrophic behavior was conducted. Structural component failure criteria was proposed considering the impact of damage accumulation on stiffness degradation. Additionally, platform overall failure criteria was proposed based on the definition of structural resistance and foundation resistance. Taking a 121 m truss jack-up platform as an example, an overall analysis model was established considering pile-soil coupling and components damage evolution. The model applicability was testified from three aspects, i.e., foundation bearing capacity, damage effect and constraint condition. Furthermore, the dynamic catastrophic evolution model of jack-up platform under the punch-through condition was investigated based on overall failure criteria. Results show that components damage evolution can reduce the ultimate bearing capacity of platform and affect its overall catastrophic evolution. Pile-soil coupling can be effectively simulated using CEL method under complex stratum conditions. For bow leg punch-through conditions, the failure mode is subjected to the combined effect of structural resistance and foundation resistance. Plastic deformation occurs in the connection area of stern leg and spudcan due to hull inclination. A change occurs as the punch-through depth increased, i.e., the buckling of leg located in the area near upper and lower guide block, which is consistent with observations in the jack-up platform after punch-through.