基于北京中心城区实测的城市边界层风场特性

为了对城市边界层的特殊风场特性进行研究,利用位于北京中心城区325 m气象观测塔,在9个不同高度布置超声风速仪,得到了2013-2017年间风速、温度连续观测的实测数据.统计分析表明:北京城区以良态风为主,盛行北风、西北风及南风,但强风主要来自西北向;除昼夜温度变化外,城市边界层的热量交换很大程度受到下垫面逆辐射影响....     

被加固混凝土构件表面粗糙度评定

被加固混凝土构件表面粗糙度是影响结构粘结加固效果的重要因素之一,粗糙度的定量描述对被加固结构界面粘结强度具有极其重要的意义。采用多齿头凿毛机对加固混凝土构件表面进行处理,提出新的粗糙度测量方法--抹砂法,对粗糙度进行评定和划分等级。试验表明：凿毛机可方便地凿出不同粗糙程度的粘结面,且均匀性好;抹砂法简单易行,快速高效,能较好地反映出构件表面的粗糙度;粗糙度的评定及其等级划分可为实际工程中混凝土表面的凿毛质量提供参考和控制标准。     

Surface pressure distribution on patterned cylinders under simulated atmospheric boundary layer winds

Extensive research has been previously conducted on pressure distribution of cylindrical models under uniform and laminar flow conditions. However, typical civil structures such as high‐rise buildings or towers are under the atmospheric boundary layer (ABL) conditions. Knowing this, the present research aims to quantify the effectiveness of surface patterns in reducing the suction zone under a simulated ABL condition. Two different surface patterns, U‐grooved and V‐grooved, were selected to be tested in wind tunnel. In addition to patterned cylinders, tests were also conducted on a smooth‐surfaced cylinder, serving as the control of the experiment. An array of roughness elements was placed at the upstream end of the test section with the purpose of inducing ABL winds within the test section. Without the ABL wind, the cylinder covered in V‐grooved riblets was most effective in reducing the suction zone followed by the U‐grooved cylinder. With the simulated ABL condition, V‐grooved cylinder continued to show decreased suction although the amount of decrease was less. Both grooved cylinders showed decreased peak pressure coefficients under the ABL condition compared to the non‐ABL condition.     

Effects of roughness blocks on atmospheric boundary layer flow over a two-dimensional low hill with/without sudden roughness change

Wind tunnel experiments were carried out to investigate the effects of roughness blocks on the atmospheric boundary layer flow over a two-dimensional low hill with maximum slope 0.21. Roughness blocks whose heights were one eighth of the hill height were arranged in a staggered pattern with a roughness density of 4.1% to model the rough conditions. Four situations with/without roughness change in the flow direction, i.e. a smooth hill in smooth flow, a rough hill in rough flow, a smooth hill in rough flow and a rough hill in smooth flow, were considered. The effects of the roughness blocks were clarified by comparing the flow characteristics over hill models, with emphasis on speedup ratio and turbulence structure. Experimental results were compared with the predictions obtained from linear models. The results show that speedup ratio depends strongly on the surface condition in the middle layer, the inviscid but rotational part of the outer layer defined by HLR theory [Hunt, J.C.R., Leibovich, S., Richards, K.J., 1988. Turbulent shear flow over low hills. Quart. J. Roy. Meteorol. Soc. 114, 1435-1471]. Adding or removing roughness blocks on the hill surface or inflow area changes the velocity deficit and creates a completely different turbulence structure in the wake.     

梁柱凹凸布置对规则巨型框架结构表面风压计算的影响

风压沿建筑物表面的分布具有复杂性,现行的GB50009-2001《建筑结构荷载规范》对风荷载平均风压取值的简化计算标准,只考虑到了大气层风压高度和建筑物体型等因素的影响。本文在风洞试验的基础上,通过对试验数据的数值分析和拟合,发现建筑物表面粗糙程度对建筑物表面的风压分布影响相当明显,并在此基础上得出了风压沿巨型框架结构不同表面粗糙程度下的简化计算公式。算例研究表明,建筑物表面不同粗糙程度引起的风压分布变化对规则巨型框架结构变形的影响较大,在设计中应予以考虑。     

赛格大厦振动事件中的大气边界层风场实测与分析

为研究深圳赛格大厦5·18出现的振动问题,根据布置在深圳的两台激光测风雷达捕获到的大气边界层风场实测数据进行分析。结果表明：在赛格大厦振动事件中,深圳上空发生了一次持续约12h的突发风气象事件;建筑顶部300~350m高空范围内最大水平平均风速为9~12m/s;全天水平风向稳定,基本保持在西南偏南风向;在200~350m高度范围,水平方向存在一定风切变;垂直方向风速虽然整体较小,但是大气存在较明显的低空对流运动;整体上,越接近地面,低空对流越强。据此并结合已有的振动观测结果,分析了大厦发生振动的可能原因是特定风况引发建筑顶部桅杆涡激共振,持时较长的平稳风气象条件使桅杆持续不断从脱落漩涡激励中吸收能量,通过大厦钢管混凝土结构传导至建筑主体,进而引发桅杆-塔楼系统的高阶共振响应。     

Boundary layer wind structure from observations on a 325 m tower

This paper is concerned with vertical distributions of mean wind speed and atmospheric turbulence characteristics over a typical urban area. The wind data were measured from more than 30 anemometers installed at 15 different height levels on the 325 m high Beijing Meteorological Tower during numerous windstorms. Profiles of mean wind speed are presented based on the field measurements and are compared with empirical models’ predictions. Aerodynamic parameters of atmospheric boundary layer are determined from the measured wind speed profiles. Furthermore, wind velocity data in longitudinal, lateral and vertical directions, which were recorded by ultrasonic anemometers at three height levels during windstorms, are analyzed and discussed. Atmospheric turbulence information such as turbulence intensity, gust factor, turbulence integral length scale and power spectral densities of the three-dimensional fluctuating wind velocity are presented and used to evaluate the adequacy of the existing theoretical and empirical models. A comparative study between the measured profiles of turbulence parameters and those estimated by AIJ-RLB-1996 and ASCE (1999) is performed. The objective of this study aims to provide useful information on boundary layer wind characteristics for the wind-resistant design of tall buildings and high-rise structures in urban areas.     

Longitudinal, lateral and torsional oscillations of a square section tower model in an atmospheric boundary layer

The longitudinal, lateral and torsional response of a square building under an atmospheric boundary layer is determined using a linear model with three degrees of freedom for different angles of incidence of wind. The experimental results are compared with existing analytical models, and an expression for predicting the lateral response for different angles of incidence and for a wide range of reduced velocities is presented.     

Profiles of mean wind speeds and vertical turbulence intensities measured at seashore and two inland sites using Doppler sodars

The authors’ group has been conducting full-scale measurements of wind velocities with Doppler sodars. It is very important to accurately assess the profiles of mean wind speeds and turbulence intensities in relation to terrain roughness. In this study, the profiles were evaluated for all data measured over a long period at a seashore and two inland sites. It is confirmed that for strong winds the profiles can be approximated by a single power law at altitudes between 50 and 340 m. The power law exponents of the mean wind speed profiles are approximately 0.1 for wind from the sea and 0.2-0.3 for wind blown over land. Those of the turbulence intensity profiles are approximately 0 and −0.2 to 0.4, respectively.     

A 2-D numerical model of boundary-layer flow over single and multiple surface condition changes

Based on the 1-D planetary boundary layer model of Weng and Taylor with E-? turbulence closure, a 2-D numerical model is developed to study the atmospheric boundary-layer flow over single or multiple changes in surface conditions. These changes can include surface roughness, thermal and moisture properties. A constant flux wall layer is used within which approximate forms for the velocity, temperature, moisture and turbulent kinetic energy profiles are obtained by analytic solution with the assumption of production equal to dissipation of turbulent kinetic energy. We also use a simple, analytic model dealing with the surface roughness change effects in neutral stratification based on the concept of an internal boundary layer. Model results for roughness changes are discussed and compared with other models and published field data.     

石灰土基层沥青混凝土面层结构路面裂缝防治

归纳了横向裂缝对石灰土基层、沥青混凝土面层结构路面产生的危害,分析了石灰土基层的特性及裂缝形成原因,并提出了施工前的预防措施和施工后的补救措施,从而确保道路行车安全和使用功能。     

A new method to calculate wind profile parameters of the wind tunnel boundary layer

This paper introduces a new method to process wind profile data of simulated atmospheric boundary layer flows in the wind tunnel so as to obtain the two important wind profile parameters—the surface roughness length z₀ and the friction velocity u_*. Instead of using the wind speed profile, the turbulent intensity profile of the turbulent surface layer, which is measured with a single probe hot-wire anemometer, is used to calculate the surface roughness length z₀. Then, the calculated surface roughness length z₀ is substituted into the mean wind speed profile of the constant flux layer to calculate friction velocity u_*. From our results this method is better than the simple regression method using the wind speed profile, which has been widely used.     

基于深反射数据的多道面波成像揭示申扎裂谷浅层S波速度结构

青藏高原普遍发育的南北向裂谷对认识青藏高原陆内造山过程和变形机制,探讨岩浆活动、成矿成藏机制具有重要的意义。位于青藏高原南部的申扎裂谷,发育在班公—怒江缝合带和雅江缝合带之间,垂直切割了冈底斯成矿带。本文针对申扎裂谷地震波信号弱、干扰强、频率变化大的特点,利用多道面波成像方法处理申扎裂谷及其邻区的81 km深地震反射剖面数据,获得了高质量的S波速度剖面。结合已有地质、地球物理资料对S波速度结构进行解释,重点研究了申扎地区的沉积层厚度以及S波高速异常特征,探讨了申扎裂谷的延伸情况,分析了浅部矿产分布与断裂的关系,讨论了热泉形成的可能成因,获得以下认识：申扎裂谷处的沉积厚度约1000 m;在剖面0～30 km范围下方1000 m以下有成矿潜力;热泉的存在印证了高温岩体的存在,为热液成矿提供了证据。     

Machining properties and surface roughness of various wood species planed in different conditions

This study was carried out to determine the planing properties and surface roughness of naturally grown Oriental beech (Fagus orientalis Lipsky.), Anatolian chestnut (Castenea sativa Mill), Black alder (Alnus glutinosa subsp. Barbata (C.A.Mey.) Yalt.), Scotch pine (Pinus sylvestris L.), and Oriental spruce (Picea orientalis (L.) Link.) grown in the eastern Black sea region of Turkey. The tests were conducted according to ASTM 1666 and DIN 4768. Test specimens were prepared from the lumber cut tangentially from logs. The machining process was carried out on a cabinet planer machine. Mainly, the effects of the rake angle and the feed speed were investigated. The cutting depth was constant with 1.6 mm. The Oriental spruce resulted in the lowest machining performance among the samples. The machining performance of the specimen increased as the feed speed or the rake angle decreased. All of the samples except the Anatolian chestnut showed lower surface roughness values. The surface roughness is found not to be affected by the feed speed, but by the rake angle. In addition, lower surface roughness values were observed for the latewood than the earlywood.     

城市加铺沥青路面常见病害及处治措施探讨

通过现场病害调查统计,结合相关力学理论和施工经验对城市道路加铺沥青路面几种普遍性以及危害性大的病害原因进行了研究与分析,并结合国内加铺层处理经验以及理论分析,进一步探讨了加铺层病害的处治措施,对提高沥青路面使用寿命有着重要意义。     

支承在弹性边界上的双曲面单层索网玻璃幕墙设计与施工

中国航海博物馆中央帆体结构为新型杂交结构,其最大亮点是位于东西帆体之间的双曲面单层索网幕墙.作为世界上首例支承在弹性边界上的双曲面单层索网玻璃幕墙,其设计与施工无先例可循,存在极大的技术风险.围绕双曲面单层索网玻璃幕墙的设计与施工,本文系统介绍了结构初始形态的确定、使用状态下的结构安全度分析、风洞试验研究、关键节点构造研究、张拉成型过程模拟、施工关键步骤等一系列问题,对同类结构的设计与施工具有借鉴价值.     

复合式路面界面层的特点及处治措施

指出复合式路面界面层的性能直接关系到路面的使用寿命,以旧水泥混凝土面板上加铺沥青混合料路面为对象,对其界面层的性能特点以及处治措施进行了较为详尽的分析,最终达到防水、抗剪、阻隔反射裂缝的目的。     

天然岩体结构面粗糙度各向异性、尺寸效应、间距效应研究

为了研究天然岩体结构面粗糙度评价结果影响因素,以重庆武隆地区大尺寸岩体结构面为例,运用三维激光扫描技术,基于Grasselli改进法描述粗糙度在不同采样方向、尺度与精度下的变化规律。结果显示:所选用的天然岩体结构面具有明显的各向异性、正尺寸效应和间距效应,因此在进行粗糙度评价时,采样方向务必与剪切方向保持一致,采样尺寸与采样间距应大于等于和小于等于有效采样尺寸与间距;为便于不同评价方法间结果对比,应保证在相同的采样参数下开展研究。     

岩体结构面三维粗糙度评价的新方法

 为了获得具有明确几何意义及理论依据的岩体结构面粗糙度评价指标,结合结构面剪切破坏机制,阐明将结构面潜在接触部分作为粗糙度评价重要因素的理论依据;将结构面粗糙度评价指标与其力学性质建立联系,提出描述结构面三维粗糙程度的新参数–粗糙度指标 。 即岩体结构面的潜在接触部分在垂直于剪切方向的面的投影面积与结构面水平投影面积之比, 体现了结构面在剪切方向的三维几何信息,具有各向异性。基于三维激光扫描技术及Matlab编程,实现了结构面三维几何模型的建立及 的计算。以工程应用实例,展示 的计算过程;研究同一结构面不同精细程度的几何模型的 ,结果表明：基于 评价的结构面粗糙度具有各向异性,且同一剪切方向的结构面 随其几何模型精细程度的增强而增大。对比研究 与Grasselli粗糙度评价方法,结果表明基于此2种方法的粗糙度评价结果具有相似性。此外, 可与结构面抗剪强度建立一定联系,为结构面抗剪强度估算模型的进一步研究奠定了基础。     

近地边界层台风观测及湍流特征参数分析

通过近海岸测风塔获取了台风达维(0518)、珍珠(0601)、派比安(0606)登陆过程中10m高度三维脉动风速数据,对近地10m高度平均风特性和湍流特性进行了分析和研究。基于台风观测结果,分析了不同来流方向和地貌状况下,风剖面指数值、摩擦速度、湍流度和阵风因子等湍流参数及其相关性。分析结果表明: 摩擦速度与平均风速呈正相关,摩擦速度随平均风速增大而增大;风剖面指数值随平均风速增大而减小;各方向湍流度随平均风速增大而减小;阵风因子与湍流度呈线性关系。通过拟合实测湍流参数相关性,提出了10m标准高度台风湍流度、阵风因子的计算式,可为台风多发区域低矮房屋的抗风设计提供参考.