Fitness-for-purpose assessment of cracked offshore wind turbine monopile

In this paper, the procedure for flaw acceptability assessment is examined through a case study of a semi-elliptical surface crack in an offshore monopile as it grows till it forms a through thickness crack. Using the procedure prescribed in an industrial standard (BS 7910), the fracture ratio, K_r is shown to increase monotonically with increasing crack depth. The load ratio, L_r, is initially insensitive to the crack depth. However, there is a rapid increase in L_r when the crack depth to thickness ratio exceeds 80%. L_r values obtained from detailed 3D FE limit analysis using elastic-perfectly-plastic material behaviour do not exhibit the asymptotic behaviour predicted by BS 7910 as the flaw transitions from deep crack to through-thickness crack. Furthermore, K_r predicted by BS 7910 is shown to be an over-estimation for the typical dimensions of offshore monopiles. The findings suggest that a structure with a deep flaw may be identified as unacceptable based on BS 7910 when it may still possess a non-trivial amount of structural residual life. This is a concern for monopiles where crack growth as a large flaw forms a significant part of the total life.     

城市轨道交通无缝线路应力放散施工及运营保障措施

城市轨道交通无缝线路应力放散施工面临有效作业时间不充裕、对供电及信号等轨旁设备影响大、可能影响次日运营等困难。以北京地区某实际工程为例,采用细致筹备、"可视化"现场分工、全方位的专业保障等措施,安全高效地完成全线的无缝线路应力放散。并详细介绍了城市轨道交通运营期的无缝线路应力放散和调整施工组织及供电、信号系统保障措施。     

基于FLAC3D的高填方路堤通道涵洞受力特性数值分析

文章以厦蓉高速公路广西境内灌阳至全州段K13＋710通道涵洞为工程实例,利用FLAC3D（快速拉格朗日分析）软件对高填方路堤中的顶板通道进行数值仿真分析,总结了高填方路堤通道涵洞的受力特性,并提出了通道涵洞设计施工中应注意的问题。     

梧州西江四桥主桥结构设计及受力分析

文章结合梧州西江四桥主桥工程方案，介绍了该主桥桥型的结构受力特性，阐述了主桥各主要构件的设计要点，并通过静力计算及动力分析，验证了该主桥结构设计方案的合理性和可行性。     

A design method of tensile triangles and low transformation temperature weld metal for reduction of stress concentration and residual stress of welded joints

Stress concentration and residual stress have a significant influence on fatigue life of welded joints. In order to reduce the stress concentration of welded joints, a mathematical design method of tensile triangles (MTT) based on bionics was applied to weld shape design. Accordingly, the stress concentration of various weld beads in the corner boxing welded joint and the fillet welded T-joint was dissected using our in-house FEM software JWRIAN. It was found that there existed a large stress concentration in the conventional welded joints, whereas those welded joints with elongated weld bead were accompanied by a lower stress concentration, especially for elongated weld bead with MTT design. Furthermore, among the weld shapes of the corner boxing fillet welded joint, the rectangle shape of weld bead had the minimum stress concentration factor (1.05). For the fillet welded T-joint with MTT design, the stress concentration of weld toe decreased dramatically with the increase of the index of designed shape, but there was a minor difference of stress concentration at weld root between the weld beads with MTT design. In addition, application of low transformation temperature (LTT) weld metal utilizing martensitic transformation to the fillet welded T-joints can produce compressive residual stress at weld toe.     

Structural response of a flexible pipe with damaged tensile armor wires under pure tension

This article studies the structural response of a 6.0” flexible pipe under pure tension considering intact and damaged conditions. In the damaged condition, several wires of the tensile armor layers are assumed to be broken. A three-dimensional nonlinear finite element (FE) model devoted to analyze the local mechanical response of flexible pipes is employed in this study. This model is capable of representing each tensile armor wire and, therefore, localized defects, including total rupture, may be adequately represented. Results from experimental tests validate the FE predictions and indicate a reduction in the axial stiffness of the pipe, a non-uniform redistribution of forces among the remaining intact wires of the damaged tensile armor layers and high stress concentrations in the wires near the broken ones. Moreover, the FE model indicates that significant normal bending stresses may arise in the pressure armor and inner carcass due to an uneven pressure distribution on these layers. Finally, the results obtained are employed to estimate the pull out capacity of the studied flexible pipe.     

Calculation of Transient Stress Field During Laser Transformation Hardening Process

IntroductionHighpowerCOzlaserssdsetransformationhardeningtechniquehasbeensuccessfullyusedinindusnyforWYears.BecausethetemPeratUrefleldislocalizedinmaterialdurllglasertransfonnationhMngProcess,highthermstrCsswillgenerateinmatgrialduringlasertfansformationhardeningProcess.Therisalsohighresidualstressinmaterial,bothintCnsionandcomPression['-'].ComPressresidualstressishelptoincreasethefatigueldrimeofthelasertreatedmaterial,butthetensilestresswillshortenthefatiguelifetmeofthelasertreatedmator…     

应力吸收层类混合料与水泥板界面直剪试验的结果分析

由于旧路面板与应力吸收层材料性质存在很大差异,层间粘层油种类及其用量大小、垂直荷载、温度条件等因素对其界面状态影响较大,利用课题组自行研制开发的LLM路面材料直剪试验仪进行室内模拟试验,并分析上述主要因素对应力吸收层与旧水泥路面板层间抗剪强度的影响。     

瀛洲大桥倒三角区浇注期间水化热温度监测及应力有限元分析

以瀛洲大桥倒三角区为研究对象,确定了温度监测方案,应用有限元分析程序ANSYS分析了箱梁混凝土的浇注温度场,得到了整个施工过程中温度场和应力场的分布规律,对三角区的浇注进行事前预测和浇注进程控制有重要的指导意义。     

基于实测动应力分析的车轴台架试验谱编制

通过长距离线路动应力测试,编制适用于车轴磁粉探伤周期优化研究的台架试验谱.首先,分析测试结果中车辆载重、线路工况、运行交路对车轴动应力的影响,并考虑车轮失圆的影响,确定不同影响因素的灵敏度;然后,进行应力谱极值推断,得到车轴外推应力谱;最后,得到台架试验谱,并开展台架疲劳试验.结果 表明:车轴最大应力截面上的最高频次应...