混凝土轨枕预应力筋张拉过程中墩头断裂原因分析

在预应力筋张拉过程中,有时在墩头部位会出现断裂现象,对于预应力筋张拉工作造成很大困扰,造成这种断裂的因素有很多。利用有限元软件Abaqus对混凝土轨枕预应力筋张拉过程进行了模拟,考虑了短钢丝、锚固板磨损等因素对张拉过程中墩头与钢丝端部应力的影响,对影响墩头断裂的因素进行分析,得出以下结论:当短钢丝长度偏差10mm时,钢丝端部的纵向应力较正常状态增大3.02%,超过钢丝极限应力达4.46%。建议在预应力钢筋张拉过程中,钢丝长度偏差控制在10 mm以内,并尽量避免短钢丝的出现。     

博茨瓦纳奥卡万戈河大桥北大核心

奥卡万戈河大桥(Okavango River Bridge,见图1)位于博茨瓦纳莫亨博市,是一座双塔斜拉桥,全长1161 m,主桥跨径布置为(100+200+100)m,两侧引桥分别长605.5 m和155.5 m。主梁采用钢梁,横向由2片箱梁组成(见图2),梁高2 m。2座钢桥塔高54 m,总重约4400 t,每座桥塔的2个塔柱截面及塔壁厚度从塔底向塔顶逐渐减小,呈现类似象牙的造型(见图3),全桥共设置72根斜拉索。     

大跨径钢筋砼拱桥拉索悬浇施工方案设计

针对一双箱双室钢筋砼拱桥，采用了拉索悬浇方案，并介绍了该方案的设计、拉索张力的控制、地锚和合拢段劲性骨架的设计及体系转换等，节约了造价，加快了工程进度。     

A Dynamic Job Scheduling Algorithm for Parallel System

One of the fundamental problems in parallel and distributed systems is deciding how to allocate jobs to processors. The goals of job scheduling in a parallel environment are to minimize the parallel execution time of a job and try to balance the user‘s desire with the system‘s desire. The users always want their jobs be completed as quickly as possible, while the system wants to service as many jobs as possible. In this paper, a dynamic job-scheduling algorithm was introduced. This algorithm tries to utilize the information of a practical system to allo-cate the jobs more evenly. The communication time between the processor and scheduler is overlapped with the computation time of the processor. So the communication overhead can he little. The principle of scheduling the job is based on the desirability of each processor. The scheduler would not allocate a new job to a processor that is already fully utilized. The execution efficiency of the system will he increased. This algorithm also can he reused in other complex algorithms.     

由平行切片图象重建血管的三维模型

CT图象可用于了解生物的组织结构，若摄取样木的数十，成百个平行切片，依次逐步分析并采样得到的各平行切片的CT图象，运用计算机就可重建其组织结构的准确的三维模型，本文提出了用数字矩阵表示CT图象的方法，定义了图象数字矩阵的“交、差、并、抽壳”的运算规则，并运用这些运算规则对血管切片的CT图象进行处理，求出血管中轴线与各平行切片的交点及血管的直径，运用OLE自动化技术控制AutoCAD实现血管三维图的重建。     

双曲柄环板式针摆行星传动中平行四杆机构运动性能分析

针对双曲柄环板式针摆行星传动中的平行四杆机构，运用动力学原理分析了杆长尺寸随机误差对机构中铰链支反力的影响，并建立了力分析模型，为在设计双曲柄环板式针摆行星传动时更好地计算各构件的强度、运动可靠性等提供了一定的理论基础．     

NEURAL NETWORK TRAINING WITH PARALLEL PARTICLE SWARM OPTIMIZER

Feed forward neural net works such as multi-layer perceptron,radial basis function neural net-works,have been widely applied to classification,function approxi mation and data mining.Evolu-tionary computation has been explored to train neu-ral net works as a very promising and competitive al-ternative learning method,because it has potentialto produce global mini mum in the weight space.Recently,an emerging evolutionary computationtechnique,Particle Swar m Opti mization(PSO)be-comes a hot to…     

小曲率半径斜拉桥拉索与索导管的侧向空间分析

为确保拉索在成桥后的减振装置安装施工便利,降低斜拉索与索导管之间的挤压风险,需要开展斜拉索与索导管的侧向空间分析。该分析基于空间索单元对斜拉桥的拉索进行精细化的数值模拟,迭代求解得到斜拉索在初始张拉力工况下的重力影响拉索线形,进而确定索梁交界位置索导管的空间角度。考虑小曲率半径斜拉桥的主梁预抛高及索塔竖向偏位和横向偏位对拉索和索导管侧向净距的影响,研究拉索与索导管的侧向挤压效应。     

钢铰线拉索式落梁防止装置设计

钢铰线拉索式落梁防止装置具有结构紧凑、静载性能好、疲劳寿命高和锚固可靠等特点,可为桥梁结构在强烈地震作用下的安全提供可靠的保障,文章对该钢铰线拉索式落梁防止装置的构成和应用设计进行介绍。     

斜拉桥运营期的斜拉索检查方法的比较分析及建议

文章通过对斜拉索的检测类型和检测方法的比较分析,建议在斜拉索的检测管理中,增加日常巡视检查,投入力量开发性能可靠的缆索攀爬设备,每年检查1次斜拉索的外观与索力,适当关注基于磁滞伸缩的斜拉索锈蚀性和断丝无损探伤技术。