并列双圆柱涡激振动的经验性模型研究

建立一种新的预报并列双圆柱涡激振动响应的经验性模型,根据特定间距比条件下旋涡脱落频率出现分支的现象,提出以两个具有不同固有频率的尾流振子来共同描述结构的近壁尾涡动力特性,同时两个振子均满足van der Pol方程,进而得到结构振子和流体振子的耦合方程组。使用该模型分别对中高质量比和低质量比的并列圆柱涡激振动问题进行数值计算,结果表明,结构的位移响应和最大振动幅值等变化规律与实验结果趋势一致,数值基本吻合。     

Modified three‐dimensional seismic assessment method for buildings based on ambient vibration tests: extrapolation to higher shaking levels and measuring the dynamic amplification portion of natural torsion

This paper presents applications of the modified 3D‐SAM approach, a three‐dimensional seismic assessment methodology for buildings directly based on in situ experimental modal tests to calculate global seismic demands and the dynamic amplification portion of natural torsion. Considering that the building modal properties change from weak to strong motion levels, appropriate modification factors are proposed to extend the application of the method to stronger earthquakes. The proposed approach is consistent with the performance‐based seismic assessment approach, which entails the prediction of seismic displacements and drift ratios that are related to the damage condition and therefore the functionality of the building. The modified 3D‐SAM is especially practical for structures that are expected to experience slight to moderate damage levels and in particular for post‐disaster buildings that are expected to remain functional after an earthquake. In the last section of this paper, 16 low to mid‐rise irregular buildings located in Montreal, Canada, and that have been tested under ambient vibrations are analyzed with the method, and the dynamic amplification portion of natural torsion of the dataset is reported and discussed. The proposed methodology is appropriate for large‐scale assessments of existing buildings and is applicable to any seismic region of the world. Copyright © 2016 John Wiley & Sons, Ltd.     

基于经验模态分解(EMD)的小波熵阈值地震信号去噪

针对EMD阈值去噪算法中阈值由经验选取以及无法有效区分各固有模态函数上有用信息的不足,本文对各固有模态函数进行小波变换,对各层小波系数进行相关处理,以突出有效信息,抑制噪声;将细节系数的有效信号和突变点置零并等分为若干区间,选取小波熵最大子区间的高频小波系数平均值作为噪声方差计算得到阈值。该阈值选取方法依据小波熵的特点,自适应地根据对应尺度上信号自身的能量特征确定该尺度阈值。将该算法应用于仿真信号和实际地震信号去噪,结果表明该方法优于基于EMD的小波阈值去噪,在提高去噪效果的同时,也更好地保护有效信号。     

土工袋技术在市政沟槽回填中的应用研究

市政工程中管线埋入地下采用的基本流程是先开挖沟槽,将开挖的原土作为渣土处理,待管线在沟槽中安放后再用二灰土石填埋沟槽,经夯实后铺设沥青或混凝土路面。为了有效利用沟槽开挖土、减少二灰土石用量,建议采用土工袋技术处理,即将沟槽开挖土装入土工编织袋后回填至沟槽中。阐述了土工袋技术原理,并依托南京市雨污分流工程,对用土工袋回填的沟槽进行了平板载荷试验、落锤式挠度检测和路面振动测试,评价土工袋沟槽的回填效果。结果表明：土工袋在提高沟槽承载力、减少沉降变形、削弱交通振动干扰等方面具有明显效果。土工袋避免弃土外运,减少了扬尘污染,不失为一种绿色、环保、经济的工程新技术。     

Scoping prediction of re-radiated ground-borne noise and vibration near high speed rail lines with variable soils

This paper outlines a vibration prediction tool, ScopeRail, capable of predicting in-door noise and vibration, within structures in close proximity to high speed railway lines. The tool is designed to rapidly predict vibration levels over large track distances, while using historical soil information to increase accuracy. Model results are compared to an alternative, commonly used, scoping model and it is found that ScopeRail offers higher accuracy predictions. This increased accuracy can potentially reduce the cost of vibration environmental impact assessments for new high speed rail lines.To develop the tool, a three-dimensional finite element model is first outlined capable of simulating vibration generation and propagation from high speed rail lines. A vast array of model permutations are computed to assess the effect of each input parameter on absolute ground vibration levels. These relations are analysed using a machine learning approach, resulting in a model that can instantly predict ground vibration levels in the presence of different train speeds and soil profiles. Then a collection of empirical factors are coupled with the model to allow for the prediction of structural vibration and in-door noise in buildings located near high speed lines. Additional factors are also used to enable the prediction of vibrations in the presence of abatement measures (e.g. ballast mats and floating slab tracks) and additional excitation mechanisms (e.g. wheelflats and switches/crossings).     

安装粘弹性转角阻尼器的海洋平台—摇摆墙体系抗震性能分析

在海洋平台摇摆墙体系基础上,在摇摆墙底部的铰接点处安装一粘弹性转角阻尼器,进行被动消能结构振动控制,利用ANSYS进行地震荷载作用下的抗震性能验算,并对阻尼器的刚度和阻尼参数进行了分析。结果表明,在摇摆墙底部施加的转角阻尼器能显著降低结构的地震反应。     

近车站地铁运行引起的环境振动的实验与分析

选取上海地铁交通9号线沿线近车站典型区段为对象,以基于LabVIEW2010开发平台的振动测试系统进行数据采集。根据现场实测数据,分析了地铁运行时隧洞中心线对应的地表处3个方向,以及距中心线不同距离地表处垂直地面方向的振动响应实况和振动特性及传播规律。结果表明,地面振动以垂直地表方向振动为主,振动幅值距离隧洞中心线越远越小,在15m左右存在放大区,且放大的敏感频率为15~25Hz。本次实验地点靠近9号线某车站,实验数值具有一定的典型性和特殊性,可为完善该领域的研究提供借鉴和参考。     

非均质土中桩端扩散虚土桩法的桩基纵向振动研究

根据桩端土应力扩散的规律,建立了桩端扩散虚土桩模型。基于该模型对非均质土中桩-土纵向耦合振动进行研究。利用复刚度传递多圈层平面应变模型,得到桩与虚土桩桩侧土的剪切复刚度。结合边界条件、初始条件和连续条件,对扩散虚土桩和实体桩动力方程从底层往顶层逐层进行求解,得到桩顶动力响应的频域解析解和时域半解析解。通过对桩端扩散虚土桩扩散角、扩散层厚度、桩侧土非均质性和桩长的影响进行计算分析,得到基于扩散虚土桩法桩-土纵向振动响应特性。研究结论可为桩基础动力设计和动态检测提供理论依据。     

小波降噪与粒子群优化综合回归爆破震动参数

爆破震动测试得到的数据常常具有较大的离散性,采用剔除错误数据和小波降噪对爆破震动检测数据进行预处理,以标准残差平方和作为爆破振动实测数据与萨道夫斯基公式拟合值偏差大小的判断依据,应用小波降噪对实测数据进行处理的方法,优化了粒子群算法对萨道夫斯基公式中的k和 的回归分析。研究结果表明,小波降噪和粒子群优化算法结合使用,能够较真实地反映爆破震动测试的真实情况,从而提高了对爆破震动测试模拟的精度。研究结果对爆破振动测试理论和工程实践具有一定的参考价值。     

考虑累积损伤效应的围岩变形特性研究

隧道爆破开挖诱发的动力扰动作用范围往往远大于其开挖进尺,同一部位围岩受到循环爆破开挖的多次扰动普遍存在累积损伤。对乌东德水电站左岸导流洞爆破开挖过程中的爆破振动和围岩变形监测进行了监测和数值分析,基于累积损伤理论,通过引入损伤判据及损伤变量,考虑计算中产生的不同程度的损伤区域的岩体参数劣化,并将劣化后的参数引入相应损伤单元进行后续开挖爆破数值模拟计算,从而对岩体爆破开挖累积损伤效应进行模拟。通过比较乌东德水电站导流洞的实测数据以及数值模拟计算结果发现,考虑累积损伤的计算结果无论是爆破振动速度还是围岩变形均更接近于实测值。对爆破开挖的分析模拟中应考虑围岩的多次循环爆破累积损伤效应。