磁流变阻尼器半主动隔振系统试验研究

介绍了对磁流变阻尼器的特性试验和将阻尼器用于隔振系统的被动与半主动控制试验。试验结果表明,阻尼力与速度之间复杂滞后环与位移激励频率、幅值和励磁电流密切相关,并呈现出一定的变化规律;被动隔振效果随励磁电流变化规律类似线性阻尼的情形,并且有调节刚度的效应;半主动控制在系统共振点附近的隔振效果优于被动隔振,但在较高频段没有优势;半主动隔振数控采样频率越低,隔振效果越差,在高频段效果劣化较明显。     

船舶中央冷却水多段比值控制系统设计

针对目前国内船舶中央冷却水系统普遍存在能耗高的问题,提出一种依据三通阀开度变化的实时改变海水变频泵组转速的控制策略。将三通阀开度分为4个区段,每个区段对应1个比值函数,根据比值函数和三通阀开度计算出变频泵组对应的频率。此外,增加smith滞环比较器作为开关函数,避免变频器在安全温度界限附近频繁切换频率对系统产生冲击。试验证明,提出的控制策略不仅实现了海水泵变频节能控制,保证系统稳定、可靠运行,而且显著降低了系统能耗。     

胶接缝连接的节段拼装桥墩抗震分析模型

采用胶接缝连接的节段拼装预应力混凝土桥墩在地震荷载作用下会在接缝区域张开,出现不连续的现象.采用常规纤维模型分析方法对这一现象进行了有限元分析.计算结果与试验结果的对比表明,建议的用素混凝土短柱模拟胶接缝的方法,可以比较准确地预测低周反复荷载作用下采用胶接缝连接的节段拼装预应力混凝土桥墩的滞回特征.     

Application of analytical model in the prediction of dynamic responses and fatigue damage of flexible risers: Part I – Improvement of analytical model considering shear deformation and varying tension effects

Flexible risers have been widely utilized for the transfer of oil and gas products from a well to production units. The components of flexible risers, unlike steel risers, experience complex contact phenomena during bending. The contact between helical wires and adjacent layers especially causes a significant level of bending nonlinearity, making it hard to estimate the structural responses. Accordingly, a large-scale dynamic analysis of flexible risers usually involves an analytical model that predicts the bending moment and axial stress of helical wires based on theoretical approaches. The analytical model consists of an axis-symmetrical model and a bending model. Among them, the bending model plays a critical role in the prediction of the bending responses of flexible risers. The conventional bending models usually neglect the shear deformation of internal layers and continuity of sliding force, which leads to a significant error of analysis. Furthermore, the previous bending models assume that the contact pressure on helical wires is constant during bending. In real operating conditions, however, most flexible risers experience a considerable change of tension that governs the slip of helical wires. Hence, the current study presents a new dynamic analysis method for flexible risers. The suggested analytical model improves the bending model based on an accurate estimation of the internal strain field considering the shear deformation and continuous sliding force. Also, this study proposes a stiffness update method to reflect the effect of varying tension in the dynamic analysis. The presented method updates the bending property of flexible risers considering the continuous change of the contact pressure from varying tension. For the validation of suggested method, the current study carries out numerical simulations with a pure bending and varying tension for the internal diameter 7 inches flexible risers. It is identified that the suggested analytical model provides accurate analysis results. Moreover, it is found that the effect of varying tension gives a significant impact on the bending behavior of flexible risers by changing the slip condition of helical wires. Part I of this series of papers describes the detailed formulation method for the analytical model and with some verification examples. The suggested analytical model is expanded to the large-scale dynamic analysis in Part II for the investigation of the effect of shear deformation and varying tension.     

对船舶抗碰撞性能分析中的两个因素的评述

从以往的对船舶的抗碰撞分析研究中,发现有两个因素在很多分析中被忽略,一个是船舶碰撞中最易破坏位置的选择,另一个是在某些船舶舷侧舱水存在时忽略了其对船舶抗碰撞性能的影响.通过对典型结构进行仿真分析,指出船舶最佳碰撞位置的选择并非一定位于通常所认为的强框架中心点处,而是取决于板与加强筋的相对刚度,以及撞击船撞头的形状,以及通过某FPSO双舷侧结构为例分析了在舷侧舱水存在的情况下,由于撞击的短时和水的惯性迟滞效应,使得提高了船舶的抗碰撞性能.对这两个因素的分析有助于今后更加完善的对船舶抗碰撞性能进行评估.     

大跨径宽箱梁连续刚构桥剪力滞效应分析

通过对大跨径宽箱梁连续刚构桥的研究,采用有限差分法计算自重作用下控制截面的剪力滞系数,并对箱梁的剪力滞效应进行分析,为此类桥梁设计提供依据。     

考虑梁柱节点黏结-滑移模型的 混凝土框架滞回性能研究

基于有限元软件OpenSEES中已有的梁柱宏观柔性节点单元和梁柱纵筋黏结滑移模型,对国内研究者已经完成的钢筋混凝土框架以及型钢混凝土框架水平低周往复荷载试验得到的滞回曲线、位移延性、滞回面积以及耗能能力等滞回性能进行有限元模拟分析,并与试验结果进行比对。根据有限元模拟结果建立基于OpenSEES软件的钢筋混凝土框架和型钢混凝土框架考虑梁柱宏观柔性节点的计算模型,为钢筋混凝土框架和型钢混凝土框架的设计计算提供一条有效途径。     

往复荷载下预制预应力混凝土梁柱接合部受力性能数值模拟

预制预应力混凝土梁柱接合部（PPC-BCC）作为结构构件间柔性连接的主要形式,在建筑、桥梁等结构中具有广阔的应用前景.文中探讨了基于三维杆系结构纤维模型程序实现复杂受力状态下PPC-BCC数值模拟的方法和途径,建立了符合PPC-BCC主要结构特性和受力特点的有限元建模方式.计算结果与试验结果对比表明：由于采用了完善的材料滞回模型和合理的有限元建模方式,本文方法及程序可以较准确用于复杂受力状态下PPC-BCC受力性能的数值模拟.     

节段拼装桥墩拟静力试验研究

采用拟静力试验方法比较承插式和节段式两种预制拼装桥墩在循环荷载作用下的滞回曲线、骨架曲线、延性性能、耗能能力、残余变形和墩柱曲率分布的异同。试验结果表明：预应力筋提高了构件的自复位能力,而耗能能力降低;承插式构件破坏形态是弯曲为主的延性破坏,骨架曲线具有强度稳定段,水平抗力和耗能能力较优;节段式构件集中在节缝区域破坏,残余位移比承插式构件小得多。     

磁滞式吊具电缆卷筒的维护

为降低磁带式吊具电缆卷筒的故障频率,必须加强维护。阐述磁滞式吊具电缆卷筒的概况。分析其故障表现及原因。提出相应改进措施和维护要点。通过维护,提高了磁滞式吊具电缆卷筒的可靠性,延长了电缆卷筒的使用寿命。