输电线脱冰过程中耐张串金具的受力仿真分析

针对脱冰过程中导线张力对输电线连接金具的破坏作用,运用 ABAQUS 软件分别建立特高压 输电线路的导线模型和耐张串连接金具的整体模型。然后基于改变密度法模拟均匀覆冰的六分裂导线和覆冰脱 落过程,研究不同步脱冰时各子导线的动态张力和导线束扭转角的变化规律,结果表明未脱冰子导线的动态最 大张力大于导线覆冰静态张力,导线动张力与导线束的转角大体呈负相关关系。最后选取导线覆冰静态张力和 脱冰引起的导线最大动张力、最小动张力、稳态张力分别施加到耐张串金具模型上进行有限元分析,发现耐张 串各连接金具的应力与导线张力的相关关系不一致;对应力较大和存在形状突变的金具进行单独分析,判断其 相应的破坏模式,为线路金具设计及优化提供了参考。     

Near ground wind characteristics during typhoon Meari: Turbulence intensities,gust factors,and peak factors

Journal of Central South University - Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal...     

大跨悬索桥索梁锚固区疲劳养护概率优化方法

合理的桥梁养护规划应在养护费用与失效风险之间找到一个合理的平衡.将养护费用分为检测费用,维修费用与失效费用,将线弹性断裂力学、结构可靠度理论、全寿命成本分析法结合起来,提出了基于全寿命周期成本的焊接构件疲劳养护概率优化的方法.考虑了检测概率、养护决策者的维修意愿、维修措施概率和失效概率等多种因素,把桥梁养护优化问题变为在焊接结构或构件满足在生命周期内最小允许可靠度的基础下,养护总费用最小的问题,并提出了简化计算方法.以青草背长江大桥索梁锚固区的关键疲劳细节养护为例,研究了主要参数对最优检测时刻的影响,研究结果表明,考虑了失效成本后,最优疲劳养护时刻提前,折现率对养护费用影响明显.当车辆荷载逐年增加时,索梁锚固区在设计基准期内疲劳破坏风险增大,应引起足够的重视.     

The effects of brief visual interruption tasks on drivers’ ability to resume their visual search for a pre-cued hazard

Driver visual distraction is known to increase the likelihood of being involved in a crash, especially for long glances inside the vehicle. The detrimental impact of these in-vehicle glances may carry over and disrupt the ongoing processing of information after the driver glances back up on the road. This study explored the effect of different types of visual tasks inside the vehicle on the top-down processes that guide the detection and monitoring of road hazards after the driver glances back towards the road. Using a driving simulator, 56 participants were monitored with an eye tracking system while they navigated various hazardous scenarios in one of four experimental conditions. In all conditions, a potential hazard was visible 4–5 s before the driver could strike the potential hazard were it to materialize. All interruptions were exactly two seconds in length. After the interruption the potential hazard again became visible for about a half-second after which the driver passed by the hazard. The nature of the in-vehicle visual interruption presented to the participants was varied across conditions: (1) Visual interruptions comprised of spatial, driving unrelated, tasks; (2) visual interruptions comprised of non-spatial, driving unrelated, tasks; (3) visual interruptions with no tasks added; and (4) no visual interruptions. In the first three conditions drivers glancing on the forward roadway was momentarily interrupted (either with or without a task) just after the potential hazard first became visible by the occurrence of an in-vehicle task lasting two seconds. In the last condition (no interruptions) the driver could not see the potential hazard after it just became visible because of obstructions in the built or natural environment. The obstruction (like the interruption) lasted for two seconds. In other words, across all conditions the hazard was visible, then became invisible, and finally became visible again. Importantly, the results show that the presence of an interruption (as opposed to an obstruction) negatively impacted drivers’ ability to anticipate the potential hazard. Moreover, the various types of interruptions had differential effects on hazard detection. The implications of this study for the design of in-vehicle displays are discussed.     

刚性索动力学系统的约化与索力测量

为解决索力动测中弯曲刚度的耦合影响问题，研究刚性索动力学系统的约化及相应的索力算法。对系统时间和空间进行坐标缩放，建立新时空坐标体系，使原方程约化为最简形式——所有系数均为1或-1，得到频率比互等关系；求解新坐标下的动力学方程，导出固支条件下的频率方程，分析其频率-梁长和频率比-梁长函数特性，提出基于频率比互等关系的双频式索力算法。给出两组10个算例均与现有文献吻合良好。研究表明：系统频率在新坐标下仅由单一参数决定；双频式算法可将索力测量的双参数反问题转化为单参数反问题，实现对索力和弯曲刚度的解耦；与其他方法相比，该方法有两个特点：①两个无量纲参数均具有明确的意义，便于工程人员掌握；②参数区间不受限，不需要对参数区间进行预判或近似处理。     

常规卤化物和高分子材料抑制尾矿库扬尘的试验

选取溶液质量浓度、溶液喷洒量以及外部风速作为变量,通过室内试验考察了常规卤化物和高分子材料对扬尘控制的效果。以抗风蚀能力和结壳抗破坏能力为响应变量。结果表明,随着抑尘剂浓度的增加和喷洒量的增加,结壳的抗风蚀性和抗破坏性可以得到提高。在卤化物溶液中,CaCl₂的抑尘性能最好。在风速为7.5 m·s?1的条件下,CaCl₂喷洒量为4.5 L·m?2,且其质量浓度为50 g·L?1时,尾矿质量损失量为0.75 g·m?2·min?1,贯入阻力为466 kPa。在高分子材料中,聚丙烯酰胺的抑尘效果最好。在风速为7.5 m·s?1的条件下,聚丙烯酰胺喷洒量为4.5 L·m?2,且其质量浓度为0.5 g·L?1时,尾矿质量损失量为0.30 g·m?2·min?1,贯入阻力为248 kPa。抑尘剂的选取可根据当地年均风速确定,年均风速较大时,可选择聚丙烯酰胺作为尾矿库抑尘剂,反之则可选择CaCl₂为尾矿库抑尘剂。      

近距离煤层群切顶留巷覆岩应力及变形响应研究

为了深入了解近距离煤层群切顶留巷上覆岩层应力及变形演化规律,以白皎煤矿B4煤层、B3煤层、B2煤层切顶成巷巷道2442、2443及2444运输平巷为研究对象,开展了3层煤回采巷道开挖物理试验研究,结果表明:①上煤层巷道切顶后,顶板卸压;煤层开挖后,采空区顶板垮落并支撑巷道顶板,顶板增压;煤层继续开挖,覆岩断裂,顶板卸压...     

Are the relative variation rates (RVRs) approximate in different cities when the same energy-efficiency reform is taken to the same building?

On the assumption that the same envelope reform is made on two buildings located in 19 cities of China, America and Europe, this paper simulates the annual heating and cooling energy consumption before and after the reform with tools of DOE-2, DeST-h and the authors' characteristic temperature method (CTM), and makes further analysis on the relative variation rates (RVRs) of energy consumption. It can be found that the absolute reductions of annual heating and cooling needs may differ up to tens of times in different cities for the same buildings with the same energy-efficient measures. On the other hand, there is no obvious difference in initial investment for the same energy-efficient reform in various cities of a country or an economic district, therefore, the energy efficiency potentiality and economic value of the same reform are completely different under various climatic conditions, which illustrates that it is very important to harmonize the local climates when selecting an energy-efficient project in different locations. However, when the same measures are taken to the same building, the annual heating RVRs are approximate and the annual cooling RVRs are also approximate in different cities, which is the common rule of building energy efficiency.     

桥梁工程教学中若干能力培养的探索

为适应土木工程专业培养方案的需要和桥梁工程自身特点,在桥梁工程教学中结合相应教学知识点的讲授,增强美学、力学分析、防灾减灾、极端事件、工程风险等能力的培养,提高学生学习兴趣,增强学生将理论知识和工程实践密切联系的能力,培养素质高和创新能力强的桥梁工程专业学生。     

Dynamic Impact Factor Induced by Idling Vehicle-Bridge Coupling Vibration

怠速车-桥耦合振动下城市桥梁动力冲击系数

刘浪^1,2,王杰²,杨洪²

(1. 省部共建山区桥梁及隧道工程国家重点实验室,重庆交通大学,重庆 400074;

2. 重庆交通大学,土木工程学院,重庆 400074)

摘要：

为计算拥堵状态下怠速车-桥耦合振动对城市桥梁的冲击作用,持续定点采集了大量拥堵车列图像,利用图像数字化处理技术,建立了3种车辆模型及6种典型城市桥梁拥堵车列模型。根据实桥参数建立了怠速状态下车-桥耦合振动有限元模型,计算了各种典型拥堵车列荷载工况下车-桥耦合振动产生的动力系数,并与规范冲击系数进行了对比。结果表明,6种拥堵工况产生的最大动力系数分别为规范值的1.15~2.67倍,说明拥堵状态怠速车-桥耦合振动产生的冲击系数较正常交通状况大。针对拥堵严重的桥梁的设计及评估,本文建议采用1.7的规范修正系数。文中提出的分析模型及方法可为本领域的进一步研究提供有益的参考。

关键词：动力冲击系数;车-桥耦合振动;交通拥堵模;规范设计值