等效热点应力法结合临界面法评估焊接接头多轴疲劳强度研究

基于焊缝本身引起的非线性分布应力自平衡的性质,在板厚方向应力峰值零点位置定义等效热点应力,结合基于临界面法的MWCM法建立评估复杂焊接接头多轴疲劳强度的方法。采用数值计算分析零点位置的变化规律,建立零点位置拟合方程。利用公开发表的试验数据以及现有的热点应力法有限元计算结果对等效热点应力法进行精度验证。结果表明,等效热点应力法和现有的热点应力法具有很好的一致性,能在一定程度上考虑厚度效应对疲劳强度的影响,可以评估多轴疲劳强度。     

Efficient methods to mitigate SCR-induced walking of short subsea flowlines

Steel catenary riser is a long-established option for subsea projects in deep-water regions. Sustained pulling force of steel catenary risers on subsea flowlines in combination with cyclic thermal load throughout the system lifetime may lead to progressive global axial displacement of subsea pipelines which has been termed as ‘walking’. One of the challenges in the deep-water industry is long-term walking of subsea flowlines in a cumulative manner. Common practice methods for walking mitigation are quite expensive operations. State-of-the-art mitigation strategies are proposed in the paper by means of modifying pipe pieces before the installation operation. Bowed pipe pieces and miter joints are two recommended approaches for walking mitigation. The presented mitigation strategies are relatively cost-effective solutions for the pipe-walking challenge and they are able to considerably cease the potential cyclic walking. Comprehensive FE analyses in ABAQUS software are performed to evaluate the proposed deformed pipelines response subject to two loading conditions. Through-life integrity of the suggested pre-deformed pipeline is assessed in terms of effective axial force, local buckles and excessive axial strains. A comparison of the presented method with conventional techniques shows the effectiveness of the proposed configuration. The proposed methods can significantly reduce effective axial force throughout the subsea pipeline by means of artificially introduced deformations. The cumulative walking of the presented method is practically zero. In addition, the influence of combined triggering mechanisms to the walking phenomenon is assessed when the pipeline is located on a sloping seabed and it is subject to non-uniform thermal loads. A parametric study is performed to improve confidence in design and provide a reasonably practical technique with an optimal shape.     

复合材料板与钢板胶接、螺接与混合对接接头的力学特性研究

对6种不同的复合材料板与钢板的连接接头,即单盖板胶接、螺接、混接,以及双盖板胶接、螺接、混接的连接接头进行了静力拉伸试验与数值研究。静力试验获得了接头的失效载荷、载荷-位移曲线以及失效模式,通过对比发现接头的承载能力与接头形式有很大关系。采用有限元方法获取了胶接接头中胶层应力分布,并研究了接头各设计参数如搭接长度、胶层厚度等对接头强度的影响规律。     

On stress concentration factors for tubular Y- and T-Joints in frame structures

This paper is written as a result of some years experience with fatigue analysis of offshore jacket structures where the connections are made as tubular joints. The hot spot stresses at the tubular joints in such analysis are normally derived based on parametric equations for stress concentration factors. These stress concentration factors are normally related to the axial force in the brace. It is observed that the hot spot stresses at the crown positions of the tubular joint in some cases are significantly affected by the local loading on the chord and the bending moment in the chord. In order to use the existing formulae in these cases some engineering effort is required to derive correct hot spot stress. This work can be avoided by using the nominal stress in the chord as the basis for calculating the hot spot stress at the crown position instead of using the axial force in the brace as basis for the analysis. This also extends the validity of the equations for stress concentration factors for T- and Y- joints in design standards. The proposed modification makes it also simpler to include the effect of joint flexibility in a proper way. The basis for a proposed revision of the equations for stress concentration factors for these joints is presented in this paper. It is considered that this modification leads to minor changes of the computer code, but that it will save analysis work for engineers and reduce the possibility of calculating incorrect fatigue lives in tubular frame structures.     

装配式空心板梁桥铰缝病害机理分析与防治措施

以某装配式钢筋混凝土空心板梁桥为例,考虑温度场变化、车辆行驶工况,采用大型的有限元分析软件ANSYS,计算并探讨了不同季节情况下混凝土空心板温度应力对板梁桥裂缝病害的影响,分析了不同车辆荷载情况下板梁桥的纵向铰缝的复杂受力状态及其破坏机理,提出了防止板梁桥结构裂缝及铰缝破坏的设计方法和构造措施。     

水下边坡防护设计与施工

实际工程中常遇到需要水下边坡防护的问题,为此,介绍两种新型的边坡防护方法——模袋混凝土边坡防护和铰接式水工垫防护。模袋混凝土技术采用织物模袋做软模具,通过混凝土泵将砂浆或混凝土充灌进模袋成型,起到护坡、护底、防渗等作用。铰接式水工垫是采用高性能、绿色混凝土制成形状一致的块体,块体之间通过特殊的连接形成一个整体,来抵抗水流的冲刷,块体之间允许适当的位移和变形,从而使该种铺面维护系统具有高度的地形适应性。     

梁柱节点混凝土不等强施工技术

针对梁柱混凝土等级不同,介绍梁柱节点混凝土不等强的处理方法和不同处理方法的特点。     

填充式桥梁伸缩缝沥青结合料低温性能的试验研究

介绍了填充式桥梁伸缩缝沥青结合料低温性能的试验研究。     

预应力混凝土梁分段灌筑接缝的静力性能研究

本文通过对具有分段灌筑接缝的三片全预应力和六片部分预应力混凝土简支梁的静力试验研究，较全面地观测和分析了符合实际桥梁施工节段龄期差的混凝土接缝的静力性能，提出了有关设计参数，可供设计及修改有关规范条文时参考。