【作者】 魏巍；

【导师】 冯启民；

【作者基本信息】 中国海洋大学 ， 环境工程， 2004， 博士

【摘要】 导管架式钢质海洋平台是目前世界上近海石油开发应用最广泛的一种海洋平台结构型式。 由于处在特殊的海域环境中，海洋平台所受到的环境荷载十分复杂。对于建在地震活跃区域的海洋平台来讲，除了波浪荷载以外，设计中还需要重点考虑地震荷载的影响。虽然地震荷载没有波浪荷载出现的频率高，并且发生时持续时间也很短，但是大的地震所造成的破坏却是十分严重的。目前还没有很好的办法能够准确地预测地震何时何地发生，以及发生多大的地震。并且，鉴于海洋平台结构本身的重要性，平台一旦遭遇超过其设防烈度的强烈地震而发生破坏，这种破坏所造成的经济损失和社会影响都将是十分严重的。 本文对导管架式海洋平台结构在地震作用下的破坏过程和破坏状态进行了深入研究。将海洋平台结构的破坏过程按照不同的特征划分了三个阶段，针对每一阶段的特征以及相应的分析方法进行了综述。并重点研究了导管架式海洋平台结构在进入破坏阶段后的动力反应特性。提出了用于地震破坏分析的结构特性时变分析方法和结构抗震安全裕度系数的概念。并对不同特性地震动作用下的导管架平台结构的破坏状态以及抗震安全裕度进行了实例分析。指出了平台结构破坏的特点以及结构中的薄弱环节。得到了一些有益的结论。为导管架式海洋平台的抗震设计以及抗震安全裕度评价奠定了分析基础。 论文的主要研究成果及创新点在于： (1) 将平台结构的地震破坏过程按照不同的特征划分为三个阶段：定常反应阶段、塑变反应阶段和破坏阶段。总结了每一阶段的状态特征和分析方法。 (2) 研究了导管架式海洋平台结构在进入破坏阶段后的地震反应特性。提出了用于结构破坏分析的方法——结构特性时变分析方法。该方法考虑了当结构中有构件发生破坏，退出工作后，剩余结构动力特性的变化以及内力的重分布，通过模型重组进行结构进入破坏阶段后的反应分析。在建立构件的破坏模型时，主要考虑了强度和稳定性两种破坏准则。 (3) 对三维空间刚架结构机动性分析的计算机自动算法进行了理论上的推导。 (4) 针对导管架式海洋平台，将其构件按照受力特点和重要程度分为三类。并根据各类构件的破坏程度将平台结构进入破坏阶段后的反应进一步划分为两种状异管架式海洋平台地震破坏状态分析研究态:中等破坏状态和局部倒塌状态。定义了相应的判别准则。 (5)在导管架式海洋平台地震破坏分析的基础上，提出了结构抗震安全裕度系数的概念。并针对平台结构进入破坏阶段后的中等破坏状态和局部倒塌状态，给出了相应的表达式。 (6)根据本文论述的理论基础和技术思路，编制了考虑结构特性时变的导管架式海洋平台结构地震破坏分析程序。为利用多条地震动输入，统计分析导管架平台地震破坏过程特点和抗震安全裕度评价提供了计算手段。 (7)为实现结构破坏过程的可视化，编制了三维动态模拟程序，可以直观地展示平台结构的整个地震破坏过程。更多还原

【Abstract】 Steel jacket offshore platforms are widely employed in offshore petroleum activities throughout the oceans of the world at the present time. For a typical offshore structure located in a seismically active region, the environmental conditions affecting offshore platform structures are very complicated and harsh. And the earthquake ground motion becomes an equally important design load of structural excitations as well as the sea waves. This is due to abruptly changing stress amplitudes during the earthquake, which can cause serious damages although the earthquake duration is very short and does not occur so frequently as the wave. Moreover, it is a pity that there is no appropriate means appears to forecast the earthquake well and truly due to limitations of state-of-the-art technology. Whereas the platform is a very important structure, once collapse induced by severe earthquake exceeding the "strength-level", the loss as well as the social influence caused by the catastrophic results will be very grave.The purpose of this dissertation is to investigate collapse behaviors and damage states of jacket offshore platforms under the severe earthquake. The collapse behavior is divided into three stages and a brief summarize of available analysis method in respect to every response stage. And special emphasis is placed on the analysis of the dynamic response characteristics after structure goes into the damage stage. A characteristics time-varying analysis method along with the concept of structural seismic safety margin coefficient is proposed. Practical design example is given on collapse analysis of a jacket offshore platform structure under earthquake with different characteristics. And some conclusions are achieved. The analysis results give useful information to seismic design and assessment of the seismic safety of steel jacket offshore platform.The main results of this study are as follows:(1) Dividing the collapse response process into three stages: stage of intact condition, stage of plastic deformation, and stage of damage. A brief outline of features of system behavior in every response stage and corresponding available analysis method are discussed.(2) The dynamic response analysis after structure goes into the damage stage is performed introducing the proposed method, characteristics time-varying analysis method.The proposed method enables the effects of the structural damage to be considered during a collapse analysis. This way of taking damage into account is important because the structural configuration at the moment in which the damage occurs is different from the un-deformed configuration and considerable redistribution of forces takes place when the damaged member fails to accomplish its structural function. And in the modeling of damaged structural members, strength damage and buckling of steel tubular members are considered.(3) A theoretical algorithm for automatically analyzing kinematical instability of three-dimension space structures are introduced.(4) For the jacket offshore platform structure, the members of which are divided into three classes by means of the forced characteristics and significances. And the different damage state of a platform structure can be defined as the reparable damage state and the failure state.(5) The concept of structural seismic safety margin coefficient is proposed. And the corresponding expression of the coefficient according to different damage state is given.(6) Based on the above theory a computer program PHFX has been developed. The program is especially aimed at collapse analysis of jacket offshore platform structures under earthquake using the proposed characteristics time-varying analysis method.(7) Another program for computer dynamic simulation is worked out. The visualization of collapse process of three-dimension structures is carried out.更多还原