破损结构地震反应简化分析法的单自由度破损模型研究

MSP(Multi-step pushover method)法是一种弹塑性推覆方法,可以评估破损状态的建筑结构的地震反应。它以地震反应谱作为输入,根据结构的动力特性分配荷载,逐步推覆,得到破损结构的最大地震反应,简便实用。作者针对MSP法中破损模型的选择和改善问题进行了专门研究和探讨。通过与非线性时程法进行对比,首次提出适用于单自由度体系的破损模型。实例计算表明,本文提出的模型可用,分析误差小,有助于MSP法进一步完善。     

Research and application of non-clay low damage temporary bridging drilling/ completion fluids system

Following the basic theory of protecting gas-reservoirs from damage with the temporary bridging technology, inert calcium carbonate (CaCO3) particles, whose diameter is consistent with the size of pores or apertures in the reservoir, were selected as the bridging agent, and modified resolvable starch was selected as filtration loss reducing particles to form the non-clay low damage temporary bridging drilling/completion fluids system (NLTDFS). Under the simulated condition of the well bottom during real drilling, NLTDFS was used to conduct dynamic and static damage experiments of cores for 48 hours, respectively, and then the experimented cores were permeated with pure nitrogen from the undamaged end to the damaged one to measure their recovery of permeability. The results showed that the permeability recovery rate of the core reached 90% or so, and the damaged depth was less than 1 cm, which demonstrates that NL TDFS has higher temporary bridging effectiveness and lower damage to the gas-reservoir than other drilling fluids system. NLTDFS has been used to drill many horizontal wells, and four of them have obtained high yield of natural gas. The yield of natural gas of LPl well reached 85 X 104 m3/day after completion with the rump pipe. The formation of the stable well wall and smooth drilling led to an API loss less than 4 mL and an HTHP loss less than 15 mL.     

某型散货轮主机膨胀节损坏原因及优化改进措施

文章就某型散货轮主机膨胀节损坏原因进行分析，从设计和膨胀节的本身入手展开研究，找出损坏原因所在，对膨胀节的选型和布置进行了改进和优化。     

沥青路面水损害的影响因素和发展过程

针对沥青路面水损害问题,分析总结了引发水损害的影响因素,并探讨了水损害的发展过程, 以期明确沥青路面水损害现象的形成机理.     

小波变换在结构损伤识别中的应用研究

针对土木工程结构的复杂性和数据的不完备性，以小波分析为理论基础，结合多尺度分析理论和数值模拟，对结构损伤识别进行了研究。主要分析了结构动力参数在损伤后的变化特征，对单自由度框架的加速度信号进行小波分析，得到结构损伤的时刻；研究了利用空间域信息对结构损伤位置的识别问题，对带裂缝悬臂梁的变形曲线进行小波变换，判定了结构损伤位置。     

重载区段接触网电气设备烧损原因分析

对大秦线重载区段接触网电气设备烧损问题进行分析,针对烧损原因提出设备改造方案和监测防范措施,有效的防止了重载区段接触网电气设备烧损问题,提高重载区段接触网供电设备的可靠性。     

Estimation of wheel–rail friction for vehicle certification

In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. However, in associated test runs the wheel–rail friction condition is difficult to handle because the friction coefficient needs to be fairly high and the friction is also generally hard to assess. This is an issue that has been studied in the European project DynoTRAIN and part of the results is presented in this paper. More specifically, an algorithm for estimating the wheel–rail friction coefficient at vehicle certification tests is proposed. Owing to lack of some measurement results, the algorithm here is evaluated in a simulation environment which is also an important step towards practical implementation. A quality measure of the friction estimate is suggested in terms of estimated wheel–rail spin and total creep. It is concluded that, tentatively, the total creep should exceed 0.006 and the spin should be less than 1.0 m^?1 for the algorithm to give a good friction estimate. Sensitivity analysis is carried out to imitate measurement errors, but should be expanded in further work.     

环境变化下基于核典型相关分析与协整的损伤识别方法

采用传统协整方法进行损伤识别时，需要变量间满足较好的线性关系，而实际工程中监测变量往往存在一定程度的非线性，这使得协整方法的有效性受到影响。为此，提出一种结合核典型相关分析与协整的损伤识别方法。首先利用核典型相关分析能有效处理非线性相关变量的优点，将低维空间存在非线性关系的监测变量映射到高维空间，使其转化为线性相关的核典型变量。然后利用协整方法能够消除变量间共同趋势的特点，对核典型变量间的共同环境因素影响进行分离，并以分离环境因素影响后的协整残差作为损伤指标进行损伤识别。最后通过芬兰Kullaa课题组的木桁架桥试验数据，对协整方法、结合典型相关分析与协整的方法、核典型相关分析和协整相结合方法这3种方法的损伤识别结果进行比较。研究结果表明：在分析非线性数据方面，核典型相关分析要优于典型相关分析；前2种方法受监测变量数目的影响较大，选择不同数目的监测变量将得到不同的识别结果，而该方法对监测变量数目不敏感；且在损伤识别的漏判率方面该方法明显优于其他2种方法。     

动荷载作用下钢结构涂装的累积损伤机理与量化模型

为研究动荷载作用下公路钢桥涂装层与基体间的协同变形和破坏机制,开发了钢结构涂装层试件的动荷载试验系统,研究了疲劳荷载作用下涂层的破坏模式、附着力、弹性厚度、应变等随循环加载次数的发展规律。结合涂层破坏模式和发展规律,构建了涂层疲劳累积损伤度的计算模型,提出了基于损伤度的涂层破坏分级方法,并结合试验结果进行了验证。结果表明:疲劳荷载将引起涂层的附着力下降、弹性厚度降低和应变松弛,进而导致涂层出现附着破坏、内聚破坏及其组合。涂层附着损伤度是涂层损伤的主要因素,且随加载次数持续增大,当加载次数较大时内聚损伤贡献突出。试验涂装体系在22万次应力循环后附着损伤度最大为0.34,内聚损伤度最大为0.27,总损伤度达0.61,属于严重损伤。提出的损伤度模型及破坏分级方法与试验规律吻合良好,可应用于公路钢桥涂装层受动荷载作用下的寿命预测。     

Low-cycle fatigue assessment of offshore mooring chains under service loading

The integrity of mooring chains is essential to the safety of a range of offshore platforms. However, mooring line failures are occurring earlier than their design lives, with a high number of these failures occurring due to fatigue. Early in the fatigue life of the component fatigue initiation processes occur, where the fatigue hotspot is sensitive to the mean load and there is plastic strain accumulation from the multiaxial stress-strain responses of the material, leading to cyclic plastic damage accumulation. The traditional SN approach suggested by mooring standards does not consider these effects, and it is proposed that this lack of consideration under low-cycle fatigue conditions is the reason for the current non-conservative fatigue assessments of mooring chains. This paper aims to develop a fatigue approach based on a critical plane multiaxial fatigue criterion for mooring chains that can consider the damage-induced by the cyclic plasticity and the mean load effect, to investigate the importance of incorporating low-cycle fatigue into the mooring chain life prediction. To develop the critical plane approach, the multiaxial stress-strain states are extracted for the critical plane at the fatigue hotspot from a finite element model of a mooring chain. This is then correlated with a fatigue life prediction provided by conventional fatigue design data. It uses a simulation of an FPSO as a case study to demonstrate the importance of low cycle fatigue, which shows that the mean load effect is significant in reducing the fatigue life for mooring chain applications, while the effect of fatigue damage-induced cyclic plasticity is limited. The fatigue damage accumulation predicted by the critical plane approach is significantly higher than that of the traditional SN approach and should be accounted for in mooring line design.