Wave-induced vibration control of offshore jacket platforms through SMA dampers

Since permanent wave-induced vibrations of offshore jacket platforms reduce the service life of the jacket structure and deck equipment and increase the fatigue failure of the welded connections, this research has used SMA (shape memory alloy) dampers to control the jacket platform oscillations. Superelasticity, high durability, and energy dissipation capability make SMA elements good nominees for the design of vibration control devices. In this research, to model the force-displacement hysteretic behavior of SMA elements their idealized multi-linear constitutive model has been implemented and the time history responses of vibration equations have been evaluated by direct integration method. To analyze the SMA damper effects on the vibration suppression of the jacket platforms, a 90 (m) high jacket located 80 (m) deep in water has been selected as a case study. Numerical results have shown that optimized SMA dampers with constant-geometry SMA bars will improve the dynamic behavior of the jacket platform under the action of an extreme regular wave. However, under the action of two irregular waves, SMA dampers with varying-geometry SMA bars will cause significant reduction in the dynamic responses of the jacket platform. The power spectral density function of the deck displacements have shown that the previously mentioned SMA dampers avoid resonance by shifting the natural frequencies of the jacket structure away from the excitation frequencies.     

Residual ultimate strength of steel plates with longitudinal cracks under axial compression–experiments

The main objective of the present study is to examine the residual ultimate strength characteristics of steel plates with cracking damages under axial compressive actions through experimental investigations. The present study is a sequel of the author's previous paper (Paik, J.K., Satish Kumar, Y.V., Lee, J.M., 2005. Ultimate strength of cracked plate elements under axial compression or tension. Thin-Walled Structures, 43, 237–272). In contrast to the previous paper which dealt with transverse cracks located in the direction normal to the axial loading direction, the present paper is concerned with longitudinal cracks which are located in parallel to the axial loading direction. Similar to the previous paper, the orientation/location and size of cracks inside the plates are varied for the present experimental investigations. The details of experimental results are documented. The database and insights developed from the present work will be useful for cracking damage-tolerant design of steel-plated structures and also for condition assessment or health monitoring of aging steel-plated structures.     

中国城市老工业园区更新的空间治理机制研究——多层次视角的分析框架

城市老工业园区更新中的空间治理涉及多元主体博弈与产业用地发展权重构问题,是当下城市研究的重要学术议题。本文以转型理论中多层次视角的形势、体制与利基为立足点,深层次挖掘城市更新中空间治理转型创新的演化过程与内在机制,提出一种不同层次多种因素间相互作用、动态演化下理解中国老工业园区更新空间治理的方法。该解释框架被应用于上海上钢十厂园区更新转型中,通过关注2004年后两次更新转型的过程和机理,研究发现：上钢十厂的更新转型是由宏观外部形势、空间利基创新、空间体制转型三个层次互动而实现的,上钢十厂两个阶段的更新均在产业转型、城市发展需求变化等宏观形势下诞生创新“新奇”,政府、社会团体或企业等空间治理行为主体共同参与推动“新奇”合法壮大并形成利基,在空间资本积累、产业类型转换中,驱使空间体制成功转型,其本质是利基层的空间创新“新奇”在宏观形势或空间体制要素的影响下解构重塑空间体制的过程。城市更新促进了老工业园区产业转型,提高了环境品质、土地利用强度和经济效益。多层次视角能结合城市更新中空间治理的外部环境、内在驱动因素和演变过程等多方面,有助于从动态演化维度理解城市更新空间变迁及转型治理的内在机制。     

The contamination of former iron and steel works sites

 Former iron and steel works sites are significant in terms of their size, number, degree of contamination, and their wide distribution in the United Kingdom. They are likely to have become chemically contaminated with a wide range of substances from the manufacture of iron and steel, and the many associated processes. Associated processes include coke-production, metal refining and finishing. Contamination by metals, inorganic and organic compounds, acids/alkalis and asbestos is common on such sites. The aim of this research was to draw together information on the contamination of former iron and steel works through a review of current literature and by the use of examples and case studies from the UK. The style of the paper is loosely based on an Inter-departmental Committee for Research in Contaminated Land (ICRCL) style guidance note, with case studies and examples. Received: 11 October 1999 · Accepted: 8 March 2000     

武钢镁碳砖首次用于盛钢桶衬砖的侵蚀机理研究

作者对我国武钢转炉盛钢桶镁碳砖的理化性能、使用条件,侵蚀情况等进行了详细的研究,在渣线处,它明显地优于镁砖.同时,在镁碳砖渐变带与反应带之间发现—镁铝尖晶石层,有延缓钢渣的锓蚀作用,并从热力学计算揭示了脱碳层及镁铝尖晶石层的形成,提出了增强衬砖寿命的具体改进措施,具有重要的理论和实际意义.     

Centrifuge modelling of SCR vertical motion at touchdown zone

Steel catenary risers (SCR) connect seabed pipelines and flow lines to floating structures used for oil and gas production in deep waters. Waves and currents induce motions of the structure and the risers. The repeated motions of the risers at the touchdown zone in turn induce loads on the seabed soil and might eventually cause fatigue damage to the risers. The analysis of riser fatigue damage is heavily dependent on the soil model. Soil behaviour at touchdown zone such as soil remoulding, stiffness degradation and deformation of the seabed at the touchdown zone further complicate the accurate assessment of riser fatigue damage, which is currently not appropriately quantified in existing design methods. This paper presents centrifuge model tests simulating the repeated vertical movement of a length of riser on clay seabed with increasing undrained shear strength with depth. During the tests, the pipe was subject to cyclic motion over fixed vertical displacement amplitude from an invert embedment of 0.5-3.5 pipe diameters into the soil. The test results show a significant progressive degradation of soil strength and diminution of excess pore water pressure with increasing number of riser penetration/uplift cycle. In view of the different types of environment loadings experienced by floating platforms and various soil conditions, tests were also conducted to investigate the effect of soil strength, riser displacement rate and loading mode on riser-soil interaction during repetitive penetration/uplift motion of the riser.     

深部软岩巷道喷射钢纤维混凝土支护技术

针对深部软岩的基本特征, 提出了深部软岩巷道支护的新思路, 即改变现有的锚喷作业顺序, 并通过在素喷混凝土中掺入适量钢纤维的方法来改善混凝土的整体力学性能, 使之更好地适应软岩巷道大变形的需要。借助数值模拟, 进行了支护方案的对比分析, 并提出了合理的支护方案。     

钢纤维掺量对钢筋混凝土桥面板冲切性能影响

通过对钢纤维体积率为0和0.38%的双向板试件进行冲切试验,得到试件的破坏形态、钢筋和混凝土荷载-应变规律等,进而量化评估钢纤维掺量对钢筋混凝土桥面板冲切性能的影响。结果表明:钢纤维体积率为0与0.38%的试件相比,相同荷载作用下后者的钢筋、混凝土应变较小;首条裂缝的出现时间推迟;试件在冲切破坏时挠度变形较大且板底表面混凝土脱落较少。     

钢板阻尼墙基于Bouc-Wen模型的模拟和工程应用研究

钢板阻尼墙抗震性能好,设计自由度大,在工程中使用越来越多。为了更高精度地模拟钢板阻尼墙的力学性能,提出基于Bouc-Wen模型的模拟分析方法。给出一种基于Bouc-Wen模型钢板阻尼墙参数辨识方法,根据试验数据和仿真结果的验证对比,文中提出的模拟方法可以较好地反映钢板阻尼墙的的力学性能曲线。该模拟方法可得到较好的仿真效果,对实际工程设计分析钢板阻尼墙对结构的抗震性能影响有高精度、数据化的帮助,可为进一步工程应用和设计分析提供参考。     

型钢高性能混凝土剪力墙恢复力模型研究

在前人研究成果的基础上,本文通过对6个型钢高性能混凝土剪力墙荷载-位移滞回曲线的分析,得出了简化的三折线型恢复力模型,并提出各个特征参数的计算公式,计算值与与试验值较为吻合。滞回规则采用考虑刚度退化和强度退化的剪切滞变模型,为型钢混凝土剪力墙的弹塑性分析提供了依据。