装配式PC箱梁刚度退化及识别的足尺试验

为了明确装配式预应力混凝土（PC）梁刚度在损伤状态下的退化规律，针对3片30 m预应力混凝土箱梁开展了足尺模型试验研究。首先，建立了损伤梁的结构静动刚度识别模型，基于跨中挠度提出了结构等代静刚度计算式，基于自振频率提出了结构等代动刚度的计算式；其次，对足尺箱梁进行了多工况的静力逐级加载和动力交替试验，分析了箱梁裂缝、挠度、频率等特征参数随荷载的演化规律，研究了损伤状态对箱梁特征参数的影响；再次，通过有限元模型修正给出了箱梁动刚度衰减系数，研究了结构静动刚度随损伤状态的衰减规律，分析了静动刚度差异的原因；最后，建立了结构静动刚度衰减系数和裂缝特征参数之间的经验回归式，并与现有研究成果进行了对比。结果表明：初始损伤状况对箱梁受荷后的裂缝统计分布特征参数有一定影响；箱梁开裂后在相同荷载下的结构等代静、动刚度衰减程度并不相同，其中最终的静刚度衰减系数为0.30，最终的动刚度衰减系数为0.80；足尺梁与室内缩尺模型梁的静刚度衰减系数并不相同。所提出的静、动刚度衰减公式较为简洁，可用于实际损伤箱梁的结构性能评估。     

基于多维平行六面体模型的动力总成悬置系统固有特性分析

工程实际中,汽车动力总成悬置系统不可避免地存在着一定的参数不确定性,且不确定参数间往往同时存在一定的相关性与独立性。本文中引入多维平行六面体模型处理系统参数相关性和独立性并存的情形,结合蒙特卡洛法提出了一种悬置系统固有特性的不确定性分析方法,并给出了方法的分析步骤。对某悬置系统的数值分析结果表明:该方法能有效处理系统不确定参数的相关性和独立性,与未考虑参数相关性的区间方法相比,该方法能获得更为合理的固有频率和解耦率区间范围;对于给定的研究模型,其左右悬置点的刚度相关性对系统固有特性的影响比较明显,在设计和研究过程中应给予重点关注。     

多塔斜拉桥加劲索涡激振动实测与时域解析模态分解

为研究多塔斜拉桥中塔加劲索涡激振动时域和频域特性，对多根加劲索开展了振动加速度测量和风速、风向观测，研究了加劲索振幅与风速和风向的关系，分析了加速度时程的时域和频域特征。采用解析模态分解法对加劲索涡激振动加速度时程进行了分解，分析了所得分量的时域和频谱特征。研究发现，在无雨和较低风速条件下，同侧并列加劲索仅迎风侧发生明显涡激振动，其峰值振动是以频率为6.25 Hz的第28阶模态主要参与为特征，为高阶多模态涡激振动，明显发振风速约为4~5 m·s^-1，风向接近垂直桥轴线，其面内振动明显大于面外。1^#加劲索面内涡激振动时程分解得到的3个相邻高阶频率时程分量显示，第28阶模态振动加速度随时间的变化，主导了加劲索振动加速度幅值的增大和减小。同时认为，解析模态分解法不仅能较好地分离含有多个密集频率分量的时域信号，且分解得到的分量不改变原信号分量的频率特征，分解分量再合成的信号与原信号时频特征完全一致。因而可采用解析模态分解法分解具有多个密集频率分量的柔性结构响应，能有助于工程结构风致响应的模态参数识别。     

频率变化对连杆动态应力的影响研究

通过试验研究验证了连杆有限元仿真模型的精确性,进一步研究了加载频率变化对连杆动态应力的影响,得到了加载频率变化对连杆动态应力的影响规律.结果表明:在加载频率较低时,连杆动态应力会随着加载频率的增加而增大,但总体来说应力值增加不大,可以忽略;在加载频率较高时,加载频率对连杆动态应力的影响很大,不可忽略.     

Theoretical analysis of natural frequency of externally prestressed concrete beam based on rigidity correction

A dynamic test on externally prestressed simply supported concrete beams separately with three typical types of tendon distributions was conducted. The results show that the natural frequencies of the beams increase with the increase in the prestressing force at,the tensioning stage, and the natural frequencies decrease after the cracks occur in the beams. Following the calculation formula of natural frequency of externally prestressed beam, which was reported in a literature, the natural frequencies of the experimental beams are calculated, and big errors are found between the test results and the calculated ones of natural frequency values. As a result, this paper has tried to adopt two methods to correct the rigidity parameter of the concrete beam in the formula for natural frequency calculation, and to use the corrected formula to calculate the frequencies of the experimental beams. The calculation results indicate a good consistency with the experimental ones, which verifies the feasibility of the corrected formula.     

计轴闭塞区段单轨条移频机车信号不上码或上红码的问题分析

通过对计轴单轨条移频区段因车速原因造成机车信号不上码或上红码问题分析,提出了具体的解决方案。     

复杂悬跨条件下的管线涡激振动分析(英文)

Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections, but also generates vortex induced vibration (VIV), which can lead to fatigue issues. The phenomenon, if not predicted and controlled properly, will negatively affect pipeline integrity, leading to expensive remediation and intervention work. Span analysis can be complicated by: long span lengths, a large number of spans caused by a rough seabed, and multi-span interactions. In addition, the complexity can be more onerous and challenging when soil uncertainty, concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a .state-of-the-art. finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation.     

基于运用载荷应力频度分布评估转向架构架焊缝疲劳寿命的方法

针对转向架构架焊缝边缘部位,运用以往有损伤实例的车辆的运行试验,获得实际作用应力频度分布.同时,采用新假定的S-N曲线及传统的疲劳设计曲线,进行了上述部位的强度及寿命评价,指出这种方法能获得较稳定的寿命评价结果.     

Estimating the ride quality characteristics of vehicles with random decrement analysis of on-the-road vibration response data

This paper describes the application of a practical analytical technique based on the random decrement method to estimate the rigid sprung mass dynamic characteristics (frequency response function) of road vehicles using only vibration response data during constant-speed operation. A brief history and development of the random decrement technique is presented, along with a summary of work undertaken on optimal parameter selection to establish the random decrement signature. Two approaches to estimate the dynamic characteristics from the random decrement signature are described and evaluated. A custom, single-wheeled vehicle (physical quarter car) was commissioned to undertake a series of on-the-road experiments at various nominally constant operating speeds. The vehicle, also instrumented as an inertial profilometer, simultaneously measured the longitudinal pavement profile to establish the vehicle's actual dynamic characteristics during operation. The main outcome of the paper is that the random decrement technique can be used to provide accurate estimates of the sprung mass mode of the vehicle's dynamic characteristics for both linear and nonlinear suspension systems of an idealised vehicle.     

Effects of noise exposure of other people on aircraft noise tolerability using a reference point approach

Reactions to aircraft noise resulting from an airport development vary considerably among individuals. This paper examines whether the noise level tolerated by individuals is affected when they compare their own situation to the situations of other people who are more severely affected by the noise. We modeled the individual noise tolerability by adopting the reference point concept and the value function of prospect theory. A questionnaire assessed different levels of noise-affected zones at a hypothetical airport. Individual noise tolerable level was measured by a prerecorded aircraft noise presented via headphones. Decision-making associated with the reported satisfaction level regarding the changes in operational flight frequency settings at the airport. An interview survey was conducted with residents near Manila airport in the Philippines. We applied genetic algorithm to jointly estimate the parameters for noise tolerability model and the value function. Results showed that individuals tolerated more overhead flights when they considered the situations of other people worse affected by the noise than they were. The tendency of noise tolerability increased with the severity of noise exposure situations of other people, but lower reactions to noise escalation. We also observed diminishing sensitivity to changes in noise relative to the noise tolerable level. The aircraft noise tolerability and the consideration of noise exposure situations of other people appeared to be a vital aspect to be considered in airport noise management and policy.