分缝拱坝的地震响应分析

采用非线性有限元法研究了带有横缝的拱坝在Ｅｌ Ｃｅｎｔｒｏ波地震作用下的响应。研究中认为坝体混凝土是线弹性体，对于横缝模拟了其连续，张开，闭合，相对滑移以及初始压力等多种受力状态。用有限元和半无限元相结合求解拱坝与库水的动力相互作用问题，算例给出了拱坝关键部位的应力和位移响应，考虑了不同水位，初始压力，抗拉强度等因素的影响，并与相应的线弹性情况的结果进行比较，最后通过综合分析对带有横缝拱坝的地震响     

Influence of aspect ratio on the flow above the free end of a surface-mounted finite cylinder

The flow above the free end of a surface-mounted finite-height cylinder was studied in a low-speed wind tunnel using particle image velocimetry (PIV). Velocity measurements were made in vertical and horizontal measurement planes above the free end of finite cylinders of aspect ratios AR = 9, 7, 5 and 3, at a Reynolds number of Re = 4.2 × 10⁴. The relative thickness of the boundary layer on the ground plane was δ/D = 1.7. Flow separating from the leading edge formed a prominent recirculation zone on the free-end surface. The legs of the mean arch vortex contained within the recirculation zone terminate on the free-end surface on either side of the centreline. Separated flow from the leading edge attaches onto the upper surface of the cylinder along a prominent attachment line. Local separation downstream of the leading edge is also induced by the reverse flow and arch vortex circulation within the recirculation zone. As the cylinder aspect ratio is lowered from AR = 9 to AR = 3, the thickness of the recirculation zone increases, the arch vortex centre moves downstream and higher above the free-end surface, the attachment position moves downstream, and the termination points of the arch vortex move upstream. A lowering of the aspect ratio therefore results in accentuated curvature of the arch vortex line. Changes in aspect ratio also influence the vorticity generation in the near-wake region and the shape of the attachment line.     

损伤与断裂耦合效应的能量理论研究及应用

以Ⅰ型裂纹为主要研究对象,基于能量法和损伤能量释放率的概念,推导出一种用于描述裂纹尖端邻域内损伤场与断裂场的耦合效应参数:损伤型能量释放率.运用双G模型理论,应用ANSYS仿真分析三点弯曲梁的裂纹扩展过程,把得到的损伤型能量释放率结果与损伤断裂的参数进行对比分析.结合盖下拱坝工程有限元模型,将人工底缝前沿损伤型的能量释放率、平均损伤、能量释放率以及损伤能量释放率4者随水位变化的发展进行比较,说明该参数可以综合考虑损伤与断裂的耦合效应.此外,建立了该参数的应用模式.     

轻钢结构厂房的生产工艺及安装要求

轻钢厂房因起诸多优点,越来越多地被应用在工业建筑中。本文从轻钢厂房的制作工艺特点及安装要求两方面,全面地介绍了轻钢厂房从制作到施工的相关要点。     

A new first-principles approach for the catenary

This paper reports on findings relating to catenaries since the publication in Expositiones Mathematicae of Denzler and Hinz’s pioneering 1999 paper, Catenaria Vera – the True Catenary. New governing differential equations and explicit solutions are derived for the catenary in positive and negative radial potentials with physical constants incorporated in the derivations. In keeping with precedent by Denzler and Hinz, a measure of historical perspective is offered as homage to Gottfried Wilhelm Leibniz, Christiaan Huygens and Johann Bernoulli, the original first-solvers of the catenary.     

求解拱坝极限荷载的增量弹性有限元迭代法

为了克服弹性补偿法每一步计算量太大的问题,结合弹塑性分析法和塑性极限分析法的优点,提出求解复杂结构极限荷载的增量弹性有限元迭代法(IEFEIM)。该方法以荷载因子β为变量,采用自适应增量调整技术,迭代逼近满足平衡条件和屈服条件的最大荷载因子βmax。与弹塑性分析法相比,IEFEIM只需材料的强度准则,不需要材料屈服、破坏后的本构关系;与塑性极限分析法相比,IEFEIM只需增量定向搜索逼近荷载因子最大值,无需开展大范围搜索的规划算法;与弹性补偿法相比,只需形成一次整体刚度矩阵,无需每一步重新形成整体刚度矩阵,可以有效地减少每次迭代的计算量。工程实例表明,IEFEIM可以有效地求得高拱坝的极限荷载,并可以给出临近极限状态时的结构性状。     

红沿河电站1000MW发电机安装

本文介绍红沿河电站一期1#发电机的参数及特点、安装工艺及过程、安装期间发生的不符合项及处理措施等。     

悬索桥架设过程中吊索长度调整的计算方法

悬索桥架设过程中,当主塔、主缆的施工误差超过规定的限值时,需通过吊索长度的调整,以消除这些误差对加劲当众施工的影响,保证成桥后桥面线形符合设计要求,为此提出了一种实用的调整吊索长度的计算方法,该法中成桥状态结构的几何形状及内力发２个阶段用几休非线性有限元法模拟整个架设过程,迭代得到,算例结果表明该法具有较高精度。     

斜拉桥施工控制可视化软件

我国目前在斜拉桥设计和施工方面的软件研制工作明显相对滞后于实际工程建设的发展需要,在经过长期从事有关科拉桥研究、设计和施工的实践之后,结合采用现代微机可视化新技术进行了这一专业软件的开发尝试,针对斜拉桥的特点,软件在施工控制、数据处理、输入方法等方面具有独特的功能,同时旨在促进我国在这一领域的研究和发展．     

无单元法在拱圈计算上的应用

无单元法(也称无网格方法)是一种新兴的数值计算方法,它是有限元等传统数值分析方法的重要补充和发展。本文针对拱坝的二维线弹性问题进行求解,计算拱圈上结点位移,计算结果由MATLAB编写的无单元伽辽金法程序运行得出。同时结合工程应用实例分析对系统进行测试评定,效果良好。