【作者】 张艳丽；

【导师】 黄一；

【作者基本信息】 大连理工大学 ， 船舶与海洋工程（专业学位）， 2019， 硕士

【摘要】 自升式平台因其高效率和低成本而被广泛应用于浅水区域,但在冰区尚无专门应用实例,国内外对自升式平台的冰区适应性均表现出浓厚的研究兴趣。在冰区作业时,如何保证冰载荷作用下自升式平台的结构安全至关重要,本文以某通用型桁架式桩腿自升式平台为蓝本,将桩腿等效为圆柱形结构,开展了冰载荷计算与结构响应研究。在冰载荷研究中,借鉴了相关规范和业界知名的研究成果,分别确定了直立和锥体结构的静冰载荷和动冰载荷时程。探讨了自升式平台与海冰的相互作用,通过文献调研将自升式平台等效为直立结构进行研究。本文分别针对自升式平台抗倾覆、抗滑移和桩靴的强度进行了分析。抗倾覆性能对自升式平台在冰区的应用有着极大的限制,需要在后续设计中予以特殊考虑;针对抗滑移分析,假定典型土壤地质条件,分别开展了简化分析和数值模拟,结果表明滑移性能基本能够满足冰区作业要求;对桩靴的屈服和屈曲性能开展评估,现有桩靴方案在应对较轻冰情时仍存在失效现象,需要对结构进行加强。针对平台总体结构强度开展研究,将上部主船体等效为杆梁结构,在保证平台设计性能基础上,通过结构等效和水动力等效,将桁架式桩腿变换为圆柱形桩腿,重点分析了平台上部位移和桩腿结构强度。轻冰情下结构的位移较大,应力超过许用应力,在冰区应用时须对桩腿结构进行加强。动力效应是本文关注的重点问题之一。利用单自由度简化得到的动力放大系数较大,但是通过时域动力分析,该系数大幅下降,平台响应仅在静力响应基础上增大了30%左右,且当初始效应逐渐衰减后甚至低于静力作用下的结构响应,可见该型自升式平台动力响应效果不明显。在设计分析中应采用时域动力分析方法,能够更加准确地确定冰载荷作用下的结构响应。增加抗冰锥是目前比较主流的降低冰载荷作用下结构响应的方法,本文通过加锥前后的响应对比讨论了抗冰锥的效果。无论从抗倾抗滑能力,还是从加速度以及结构应力响应上,加锥对自升式平台都有着明显的性能提升。更多还原

【Abstract】 Due to its high efficiency and low cost,jack up platform has been widely used in shallow water area.But there is no specific application in ice area.Native and foreign researchers show strong interest in this field.To ensure the structural safety of jack up platform under ice load is very important.In this paper,based on a general-purpose truss type jack up platform,the truss legs are replaced by cylindrical ones to study the ice load and structural response.In the study of ice load,the static ice load and dynamic ice load time history of vertical and cone structures are determined respectively by referring to relevant codes and well-known research results in the industry.The interaction between the jack up platform and sea ice is discussed.The jack up platform is equivalent to a vertical structure through literature research.Stability is an important performance index of jack up platform in ice area.In this paper,the anti-overturning,anti-sliding and spud can strength of jack up platform are analyzed.The antioverturning performance has a great limit on the application of jack up platform in ice area,which needs to be specially considered in the design.According to the anti-sliding analysis,assuming the typical soil geological conditions,the simplified analysis and numerical simulation are carried out respectively.The results show that the sliding performance can basically meet the operation requirements in ice area.The yield and buckling performance of pile shoes are evaluated.In the case of light ice,some spud can structure fail,so the structure needs to be strengthened.Research on the overall structural strength of the platform has been performed.The lattice legs were equivalent to the cylindrical types,with hydrodynamic and structural equivalence to simulate the design performance of the original platform.The displacement of the upper platform and the structural strength of the pile leg are mainly analyzed.Under light ice condition,the displacement of the structure is large and the stress exceeds the allowable value,so it is necessary to redesign and strengthen the legs when it is used in ice area.The dynamic effect is one of the key issues in this paper.A very large dynamic amplification coefficient is obtained by using the single degree simplification method.However,through the time-domain dynamic analysis,the coefficient is greatly reduced,and the response is only increased about 30% on the static basis.Moreover,when the initial effect gradually decreases,the response is even lower than the structural response under the static time history.The dynamic effect of response is not obvious.The time-domain dynamic analysis method should be used in the design analysis,which can more accurately determine the structural response under the ice load.At present,increasing ice-resistant cone is one of the main methods to reduce the structural response under ice load.In this paper,the effect of ice-resistant cone is discussed by comparing the response before and after adding ice cone.For anti-overturning,anti-sliding ability,acceleration and structural stress response,the performance of jack up platform is improved obviously by adding cone.更多还原