施工过程分析在ANSYS中的实现

在结构施工过程中,结构受力体系、边界约束条件、荷载分布在不断的改变。利用大型有限元软件ANSYS的“生死单元”,可以进行结构施工过程分析。主要介绍了“生死单元”的机理,并举例分析了仅与“杀死单元”相连接的节点的约束问题,使其能较好的模拟结构施工过程。     

带卸荷板的方块码头墙身位移对墙后土压力的影响

土压力与挡土墙体的位移密切相关,现行规范中采用主动土压力理论计算带卸荷板的方块码头墙后土压力是不完全准确的。根据此类码头结构特点,对地基条件好、基床厚度薄的方块码头墙身位移特性进行论述,对规范方法提出修正意见。依托于某工程实例,采用数值分析方法对码头墙身位移和墙后土压力进行模拟,并与规范公式计算结果进行对比,得出墙底处修正系数可取1.84,卸荷板处可取1.34,可为类似特点的工程土压力计算提供参考。     

冰荷载作用下护岸结构数值模拟

季节性冰冻河流春季开江产生的流冰会严重威胁堤防建筑物的安全,开展流冰对结构物的碰撞规律研究十分必要。为此,以松花江汤原县胜利堤护岸结构为例,利用ANSYS/LS-DYNA软件,基于结构地质地形,考虑松花江春季江面开化流冰情况,建立计入冰荷载作用下的护岸结构数值分析模型,开展护岸结构在冰排撞击作用下的有限元分析研究,理清结构承载变化规律,为季节性冰冻地区护岸结构的设计及后期维护提供理论参考和技术支持。     

Simulating ad-hoc demand-responsive transportation: a comparison of three approaches

Transport models are used to evaluate new infrastructure and public transport services, varied levels of demand, and new ideas for demand management. Exploring these proposals virtually is easier than implementation and testing in situ. However, existing models are based around traditional forms of transportation. As part of a feature analysis using a case study approach, three different simulation packages (a simple custom-developed package, traffic microsimulation, and agent-based simulation) are used to develop and demonstrate simulations of demand-responsive transportation (DRT) and analyze the advantages and disadvantages of each simulation approach for evaluating DRT. While the simulations display some relational replication (meaning they produce similar relational patterns with respect to certain variables), they do not show distributional replication (that is, the value of the results is not statistically similar), meaning that under- or over-estimation of predicted travel could occur. Recommendations for the application of each modeling approach are made.     

Fueling for contingencies: The hidden cost of unpredictability in the air transportation system

The aviation community is increasing its attention on the concept of predictability when conducting aviation service quality assessments. Reduced fuel consumption and the related cost is one of the various benefits that could be achieved through improved flight predictability. A lack of predictability may cause airline dispatchers to load more fuel onto aircraft before they depart; the flights would then in turn consume extra fuel just to carry excess fuel loaded. In this study, we employ a large dataset with flight-level fuel loading and consumption information from a major US airline. With these data, we estimate the relationship between the amount of loaded fuel and flight predictability performance using a statistical model. The impact of loaded fuel is translated into fuel consumption and, ultimately, fuel cost and environmental impact for US domestic operations. We find that a one-minute increase in the standard deviation of airborne time leads to a 0.88 min increase in loaded contingency fuel and 1.66 min in loaded contingency and alternate fuel. If there were no unpredictability in the aviation system, captured in our model by eliminating standard deviation in flight time, the reduction in the loaded fuel would between 6.12 and 11.28 min per flight. Given a range of fuel prices, this ultimately would translate into cost savings for US domestic airlines on the order of $120–$452 million per year.     

在建盾构隧道突发管片破损病害成因分析及治理措施研究北大核心CSCD

盾构法广泛应用于我国城市轨道交通隧道的建设中,盾构管片的病害问题也越发受到重视。文章针对某地铁在建盾构隧道突发管片破损病害,绘制了管片破损病害展布图,分析了相关资料和检测数据,明确了病害的成因机理,制定并实施了相应治理措施。研究结果表明:管片背后大范围空洞导致围岩对隧道的约束不足,引起已成型隧道在盾构机反推力和扭矩、同步注浆浆液浮力、刀盘水土压力和扭矩等作用下发生类压杆弯扭失稳是导致该病害的主要原因;隧道变形监测数据表明"背后注浆填充+破损部位修复"两阶段治理措施取得了良好的治理效果;盾构隧道施工过程中,应严格管控同步注浆质量,防止隧道轴线偏移引起盾构管片发生开裂破损等病害。     

提高柴油机供油系统可靠性探讨

柴油机的供油系统是柴油机的重要组成部分,是柴油机的心脏与血脉,它对柴油机的燃烧以及柴油机的动力性、经济性、可靠性和排放特性等一系列性能指标有着有直接的影响。统计数据表明,在柴油机的各种故障中,供油系统的故障比例最高．本文对柴油机供油系统进行可靠性分析,并对如何提高其可靠性提出建议．     

液压泵噪声的统计分析和试验研究方法

结合液压泵降噪实践对液压泵噪声的统计分析和试验研究作简要述评。指出“液压泵噪声的统计分析及频谱测试”为估算同类液压泵噪声总级并估计其频率分布提供了简便有效方法,为正确设计液压系统使其工作在低噪声工况提供了依据;对“低噪声液压泵”的选型和液压泵降噪措施的发展有益。     

深海钛合金压力容器在静水压力作用下的弹塑性分析

利用MSC.Marc Mentat 2005通用有限元软件对深海探测用压力容器受静水压力作用时的弹塑性失稳问题进行了计算与分析,弹性失稳数值计算的结果与用现有规范计算公式所得结果一致,均大于塑性失稳数值分析时的临界载荷。由此得出结论,对于厚壁且形状复杂的压力容器的失稳计算,用理论公式或仅用厚壳单元的弹性失稳分析是不够的,应该用3维立体单元的弹塑性失稳计算才能给出比较精确的强度预测。MSC.Marc Mentat2005强大的计算和仿真功能有效地模拟了深海精密探测容器受静水压力作用时的弹塑性失稳问题,为深海精密探测容器在材料、外观等方面做进一步的设计改进提供了可靠的工具。     

水下目标深度测量误差源分析

首先研究了在深海环境下,采用基于三阵元垂直线列阵的水声探测系统进行水下目标深度测量的基本原理.然后从随机误差和阵元配置偏差的角度,对水下目标深度测量的误差源进行了理论分析,并推导了相关公式.此外,对于相干多途水声信道干扰给水下目标深度测量精度的影响,也作了初步的理论分析.通过仿真实验,总结出各误差源对水下目标深度测量精度影响的规律,研究结果为进一步开展水下目标深度测量研究、提高测量精度奠定了基础.