共查询到20条相似文献，搜索用时 15 毫秒
1.
This paper presents a node shift method to find the optimal distribution of nodes in single-layer reticulated shells. The optimization process searches for the minimum strain energy configuration and this leads to reduced sensitivity in initial imper- fections. Strain energy sensitivity numbers are derived for free shift and restricted shift where nodes can move freely in the 3D space or have to move within a predefmed surface respectively. Numerical examples demonstrate the efficiency of the proposed approach. It was found that optimized structures achieve higher ultimate load and are less sensitive to imperfections than the initial structure. The configuration of the final structure is closely related to factors like the initial structural configuration, spatial conditions, etc. Based on different initial conditions, architects can be provided with diverse reasonable structures. Furthermore, by amending the defined shapes and nodal distributions, it is possible to improve the mechanical behavior of the structures. 相似文献
2.
文章阐述了云录播的概念和模型,并从逻辑和物理结构上对云录播的构成与功能进行了详细的阐述,结合学校实际的云录播建设案例,介绍了云录播系统的建设思路和部署方法,并对基于云录播技术的应用进行了探索,为大规模的微格教室或者录播建设提供参考。 相似文献
3.
Initial pre-stress finding procedure and structural performance research for Levy cable dome based on linear adjustment theory 总被引：1，自引：1，他引：1
ZHANG Li-mei CHEN Wu-jun DONG Shi-lin 《浙江大学学报(A卷英文版)》2007,8(9):1366-1372
The cable-strut structural system is statically and kinematically indeterminate. The initial pre-stress is a key factor for determining the shape and load carrying capacity. A new numerical algorithm is presented herein for the initial pre-stress finding procedure of complete cable-strut assembly. This method is based on the linear adjustment theory and does not take into account the material behavior. By using this method,the initial pre-stress of the multi self-stress modes can be found easily and the cal-culation process is simplified and efficient also. Finally,the initial pre-stress and structural performances of a particular Levy cable dome are analyzed comprehensively. The algorithm has proven to be efficient and correct,and the numerical results are valuable for practical design of Levy cable dome. 相似文献
4.
A double strut cable dome structural system was presented to improve the mechanical behaviour of a cable dome. This structure has good stability and is convenient to construct. To investigate its construction method and static performance, a structural model with a 6-m diameter was designed. From the nodal equilibrium equation, the calculation formulas for the prestress distribution with self-weight considered were deduced. Two types of construction methods, namely, assembling at high altitude and integral lifting, were adopted in the shape-forming process of the double strut cable dome, monitoring the internal force of the cable-strut components and the structural deformation. According to loading tests under full-span load and half-span load, the static behaviour of the structure was obtained and compared with the results from finite element analysis. Using the formulas deduced in this paper, the actual initial prestress considering self-weight for a double strut cable dome can be obtained accurately. This structure was suitable for tensioning the outer diagonal cables to apply prestress. Combined with the construction method for integral lifting, the difficulty and workload of the construction process can clearly be reduced, making the structure favourable for engineering application. Under an external load, the internal force of the ridge cables and inner diagonal cables decreases and the internal force of the other components increases. The results of the model tests were in good agreement with those of the finite element analysis. 相似文献
5.
Active control experiments on a newly proposed herringbone ribbed cable dome are described in this study. The cables of the dome are designed to have the ability to change length in order to adjust the geometrical configuration and the force distribution of the structure. Thereby, the dome is adaptable to different load cases. To begin with, for achieving the control amount for the active control test, an active control algorithm based on a nonlinear force method is presented. Then, an assembly and pre-stressing procedure is implemented. Active adjustment tests on three possible types of adjustable cables are performed to provide a practical method for the following active control test. The active control test demonstrates the applicability of the active control algorithm to achieve both force control and shape control. The method can be used to prevent failure of the cable domes due to slackening of the ridge cables and excessive displacements of the central section of the cable dome. The experiments verify the proposed control algorithm and the feasibility of the cable dome to adapt to excessive full span load and maintain the integrity of the structure. 相似文献
6.
The construction of the cables is a key step for erecting suspen-dome structures. In practical engineering, it is difficult to ensure that the designed pre-stresses of cables have been exactly introduced into the structures in the site; so it is necessary to evaluate the influence of the variation of the pre-stresses on the structural behavior. In the present work, an orthogonal design method was employed to investigate the pre-stressed cables'sensitivity to the suspen-dome system. The investigation was concentrated on a Kiewitt suspen-dome. Parametric studies were carried out to study the sensitivity of the structure's static behavior, dynamic behavior, and buckling loads when the pre-stresses in the cables varied. The investigation indicated that suspen-dome structures are sensitive to the pre-stresses in all cables; and that the sensitivity depended on the location of the cables and the kind of structural behavior. Useful suggestions are given at the end of the paper. 相似文献
7.
The construction of the cables is a key step for erecting suspen-dome structures. In practical engineering, it is difficult to ensure that the designed pre-stresses of cables have been exactly introduced into the structures in the site; so it is necessary to evaluate the influence of the variation of the pre-stresses on the structural behavior. In the present work, an orthogonal design method was employed to investigate the pre-stressed cables' sensitivity to the suspen-dome system. The investigation was concentrated on a Kiewitt suspen-dome. Parametric studies were carried out to study the sensitivity of the structure's static behavior, dynamic behavior, and buckling loads when the pre-stresses in the cables varied. The investigation indicated that suspen-dome structures are sensitive to the pre-stresses in all cables; and that the sensitivity depended on the location of the cables and the kind of structural behavior. Useful suggestions are given at the end of the paper. 相似文献
8.
陈铁冰 《深圳职业技术学院学报》2009,8(3):38-41
文章提出基于神经网络重要抽样法的结构可靠度评估方法,该方法通过训练神经网络,建立随机变量与结构响应之间的非线性映射关系,模拟结构极限状态方程,采用优化算法计算设计点．在重要抽样法中利用训练好的神经网络代替有限元求解器进行数值计算．结果表明,所训练的神经网络能够有效地模拟真实的结构极限状态方程,结构失效概率计算结果具有很高的精度,调用有限元分析的次数显著减少,有效地提高了计算效率． 相似文献
9.
预应力钢结构微尺模型实验技术 总被引：2，自引：0，他引：2
为研究微尺模型中预应力拉索的相关实验技术,以竖向预应力钢结构体系中2个典型结构为对象进行了试验,主要阐述微尺试验模型的设计、预应力的施加与测定方法、外荷载的施加方法,并着重分析了这些方法的优缺点。结果表明,螺杆拧张法施加预应力能够较好地模拟拉索只受拉不受压的受力特点,但存在系统误差,与该法配套宜采用传感器测试拉索力;丝扣拧张法施加预应力相对比较精确,但不便于更换拉索,与该法配套宜采用应变片测试拉索力。 相似文献
10.
Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon. 相似文献
11.
This paper proposes a new numerical simulation method for analyzing the parametric vibration of stay cables based on the theory of nonlinear dynamic response of structures under the asynchronous support excitation. The effects of important parameters related to parametric vibration of cables, i.e., characteristics of structure, excitation frequency, excitation amplitude, damping effect of the air and the viscous damping coefficient of the cables, were investigated by using the proposed method for the cables with significant length difference as examples. The analysis results show that nonlinear finite element method is a powerful technique in analyzing the parametric vibration of cables, the behavior of parametric vibration of the two cables with different Irvine parameters has similar properties, the amplitudes of parametric vibration of cables are related to the frequency and amplitude of harmonic support excitations and the effect of distributed viscous damping on parametric vibration of the cables is very small. 相似文献
12.
以某双塔单索面人行钢斜拉桥为对象,采用Midas Civil建立全桥空间杆系有限元模型,进行恒载、活载和承载能力极限状态作用下结构受力性能分析,同时开展该桥的动力特性分析。研究表明:对于该异形斜拉桥,活载引起的主梁和主塔弯矩效应较恒载作用下的结果更加显著;承载能力极限状态作用下,该桥主梁、主塔、斜拉索等主要承重构件的最大应力均小于材料容许应力,满足规范要求;动力特性分析结果表明主梁面内刚度和主塔面外刚度较小,此外遮阳棚的局部振动在高阶振型中所占比例较大,在地震作用下可能发生破坏;该桥的一阶竖向自振频率为1.92 Hz,不满足现行规范要求,建议采取有效的减振措施来控制人致振动响应。 相似文献
13.
王璐 《重庆第二师范学院学报》2012,25(6):24-26,35
提出了一种基于CAN总线的多级分布式发电机组电气性能测试系统。利用数字信号处理器（DSP）及三菱M16C/6N系列单片机实现了对电气参数的采集和控制,设计了一种基于AT89S52单片机的智能负载,可自动根据测试需要调节负载大小,利用工控机和组态控制软件,实现了对发电机组多个电气参数的远程实时监测和综合分析。提出了一种基于离散傅里叶变换（DFT）的同步交流采样算法,通过＂三点＂法实现了频率的跟踪,提高了采样精度。实际应用表明,系统组态灵活、测试精度高、可靠性高。 相似文献
14.
肖一 《福建工程学院学报》2015,(4):323-326
温度效应对主缆设计和施工有重要影响。在已有研究基础上,推导了分析主缆非均匀温变场问题的解析方法,其中的温度和静力应变均以无应变状态为参考态并考虑了主缆变形前后截面的变化,在理论上较已有方法更为合理,算例表明了其正确性。 相似文献
15.
电力系统动态模拟实验室的调度自动化 总被引：1，自引：0，他引：1
介绍了湖南大学电力系统动模实验室SCADA系统的硬件结构,即包括厂站端远程终端设备(RTU)、信息传输通道和主站端计算机系统三部分。详细阐述了电力系统调度自动化和数据库的各部分的构成、功能及其操作。总结了系统的图形显示功能,调度自动化系统的故障现象和维护处理方法,完成了负荷部分的SCADA组态及其组态过程的原则和注意事项。 相似文献
16.
运用双剪统一屈服准则,对线性荷载的两种不同分布形式作用下的固支圆板进行了弹塑性分析,分别得出了相应的统一解形式。选择不同的参数。利用本文的解可以得到一系列不同屈服准则下的极限荷载和极限荷载随不同屈服准则的变化曲线。所给出的统一解适用于各种拉压强度相同的材料。文献中已有的Mises解是本文解答的逼近。计算结果表明,应用双剪统一屈服准则可以得出更符合材料性质的极限荷载,可以更好地发挥材料的强度潜力,在工程应用中取得显著的经济效益。 相似文献
17.
Based on elastoplastic model, 2D and 3D finite element method (FEM) are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio. 相似文献
18.
Zhi-jiang Jin Cheng-hang Jiang Xian-ping Wan Po Chen Xiao-fang Wang 《浙江大学学报(A卷英文版)》2010,11(6):440-448
With von Mises yield criterion, the loading range of Net Section Collapse （NSC） Criteria is extended from combined tension and bending loadings to combined bending, torsion and internal pressure loadings. A new theoretical analyzing method of plastic limit load for pressure pipe with incomplete welding defects based on the extended NSC Criteria is presented and the correlative formulas are deduced, the influences of pipe curvature, circumferential length and depth of incomplete welding defects on the plastic limit load of pressure pipe are considered as well in this method. Meanwhile, according to the orthogonal experimental design method, the plastic limit loads are calculated by the finite element method and compared with the theoretical values. The results show that the expressions of plastic limit load of pressure pipe with incomplete welding defects under bending, torsion and internal pressure based on extended NSC criteria are reliable. The study provides an important theoretical basis for the establishment of safety assessment measure towards pressure pipe with incomplete welding defects. 相似文献
19.
为解决多租用者应用程序所面临的经营规模和运行特性等最佳配置策略问题,创建了名为S-BM基准的模拟供应商关系管理应用程序。S-BM基准作为代表基准测量的一种方式,可以用来评估多租用者应用程序和资源利用配置问题。通过两组设备对定制的负载生成器进行评测,包括在12个从小到大商业规模的代表负载中测量系统应用程序性能,以及在多样基础设施配置基础上对比其性能和不同负载成本等。实验研究负载与性能之间的关系,帮助找到用于多租用者应用程序的最优配置策略,结果表明,通过在共享环境下重新配置大和小交易应用程序,负载性能在同样资源成本情况下增长了30%。 相似文献
20.
Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexibility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers. 相似文献