南极普里兹湾海域湍流扩散系数估计

基于Thorpe尺度方法,利用CTD数据,计算了南极普里兹湾海域的Thorpe尺度和湍流扩散系数,分析了观测区域(64°～69°S,66°～80°E)湍流翻转现象的强弱及分布。结果表明,在海底和地形粗糙区存在较大的Thorpe尺度(较强湍流翻转)和湍流扩散系数,湍流扩散系数最大值能达到10^-2m²/s量级,比平坦开阔海洋高2～3个数量级,部分观测站位的湍流扩散系数和湍动能耗散率表现出大-小-大的垂向分布结构,总水深较深的区域尤为明显;深水区域的浮力频率在海表面到500 m层比较大,浅水区域该现象不明显;湍动能耗散率在(67.25°S,73°E)周围和经度为78°E的各站位都表现相对较大,能达到10^-6 w/kg量级,个别站位甚至能达到10^-5 w/kg量级。     

胶结充填体三轴压缩变形破坏及能量耗散特征分析

充填体的变形破坏、能量耗散与围压的变化密切相关,通过开展不同灰砂配比、浓度的充填体单轴、三轴压缩试验,基于系列试验结果,研究了不同围压加载阶段充填体的变形特征、破坏模式及能量耗散与围压的内在关系。结果表明,随着围压的增加,充填体的峰值应变随之增大,且两者呈线性相关;低围压时充填体呈现脆性破坏,表现为应变软化特征,随着围压增大,充填体由脆性向应变硬化转化,灰砂比越大、浓度越高,充填体发生脆-延性的临界围压值越大。充填体的破坏裂纹发展形式各异,大致可分为单一、平行、交叉和复合4种类型;宏观破坏表现主要呈“X”状、“Y”状剪切模式,破坏面的类型主要分为：直线式光滑摩擦面、圆弧式破碎摩擦面、直线式破碎摩擦面以及台阶式破碎摩擦面。充填体的峰值强度与围压也呈正线性相关,内摩擦角对灰砂比的敏感性要高于浓度。围压的增大能够相当程度上提高充填体各阶段的应变能,峰前、峰后能耗量、单位体积变形能以及总能耗与围压皆呈正相关性。     

落石冲击作用下被动柔性防护网整体结构试验

针对被动柔性防护网受力系统,介绍了被动柔性防护网在国内外的应用和研究现状,阐明了被动柔性防护网的构成和传力机理,揭示其抵抗落石冲击的基本原理。为分析被动柔性防护网整体受力机理和响应特点,进行了在落石作用下被动柔性防护网足尺模型的冲击试验,分析了被动柔性防护网受到冲击之后的整体变形以及减压环、钢柱等关键构件的耗能及其破坏机理,为被动柔性防护网的结构计算分析与设计提供一定的参考依据。     

密实散粒体剪切破坏能量演化的离散元模拟

砂土等散粒体在剪切过程中的能量存储及耗散是其宏观力学响应的深层原因,但因量测难度较大而研究较少。将考虑抗转动的接触模型引入离散元软件PFC2D,基于热力学第一定律建立各种能量量测方法,并在平面应变双轴压缩试验中采用该方法统计密实散粒体在剪切过程中的能量演化规律。采取了4种耗散类型,即滑动-滚动（S-R）、滑动-非滚动（S-NR）、非滑动-滚动（NS-R）和非滑动-非滚动（NS-NR）。结果表明：密实散粒体加载时能量耗散以滑动摩擦为主;且小应变加载阶段,外力功主要转化为弹性应变能,但同时也存在均布于试样的耗散能;随着应变的增加,外力功的转化形式逐渐过渡为以耗散能为主,且集中分布在带状区域内;各个加载阶段的摩擦耗散均存在各向异性。     

Seismic response of steel frame structures with hybrid passive control systems

The concept of the hybrid passive control system is studied analytically by investigating the seismic response of steel frame structures. Hybrid control systems consist of two different passive elements combined into a single device or system. The hybrid systems investigated in this research consist of a rate‐dependent damping device paired with a rate‐independent energy dissipation element. The innovative configurations exploit individual element strengths and offset their weaknesses through multiphased behavior. A nine‐story, five‐bay steel moment‐frame was used for the analysis. Six different seismic resisting systems were analyzed and compared. The conventional systems included a special moment‐resisting frame (SMRF) and a dual SMRF–buckling‐restrained brace (BRB) system. The final four configurations are hybrid passive systems. The different hybrid configurations utilize a BRB and either a high‐damping rubber damper or viscous fluid damper. The analyses were run in the form of an incremental dynamic analysis. Several damage measures were calculated, including maximum roof drift, base shear, and total roof acceleration. The results demonstrate the capability of hybrid passive control systems to improve structural response compared with conventional lateral systems and to be effective for performance‐based seismic design. Each hybrid configuration improved some aspect of structural response with some providing benefits for multiple damage measures. The multiphased nature provides improved response for frequent and severe seismic events. Copyright © 2011 John Wiley & Sons, Ltd.     

新型开孔H型钢阻尼器有限元分析

设计了分别开椭圆形孔和菱形孔的2种新型H型钢耗能器,阐述了它们的构造与耗能原理。采用有限元软件ABAQUS对开椭圆形孔、菱形孔和条形孔这3种新型耗能器的耗能性能进行数值分析,研究了开孔形状、肢宽与肢高等参数对新型耗能器耗能性能的影响。分析结果表明：新型H型钢耗能器具有饱满的滞回曲线,屈服位移较小、耗能性能稳定,耗能器的屈服位移、初始刚度和等效阻尼比随各肢钢板宽度增大（或高度减小）而增大;在开孔率相近或者肢宽相同的情况下,菱形孔H型钢耗能器的等效阻尼比要比条形孔和椭圆形孔的大,且应力分布更加均匀。     

不同构造参数对圆环耗能器性能的影响分析

设计了13组不同构造参数的圆环耗能器,采用ABAQUS软件对安装在支撑框架结构中的圆环耗能器进行参数分析,研究圆环钢板厚度、圆环外直径、支撑角度、圆环钢板局部削弱形式和削弱深度对圆环耗能器性能的影响。研究结果表明：圆环耗能器滞回曲线稳定、饱满,塑性耗能能力强;随着圆环钢板厚度的增加或者圆环外直径的减小,圆环耗能器初始刚度和屈服力增大;支撑与横梁之间的角度对圆环耗能器性能有一定影响,交叉支撑角度宜取45°左右;圆环钢板局部削弱圆环耗能器比不削弱圆环耗能器具有更好的耗能效果;圆环钢板局部削弱形式宜采用圆弧式,且钢板削弱深度宜控制在圆环钢板宽度的20%~30%。     

Energy dissipation through wind-generated breaking waves

Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.     

“门”地貌单元的能量耗散和过程机制

基岩岛屿组成的"门"地貌单元是珠江河口区别于世界其他河口的重要地貌特征之一。文章基于重整化群k-ε湍流模型(RNG k-ε)的FLOW3D流体计算模型研究了"门"地貌单元的时均动力结构及湍流能耗特性。"门"地形致动力结构伴随不同类型能耗区。根据能耗空间分布特性可分为核心区(A1区)、混合区(A2区)、上游区(A3区)、下游区(A4区)。"门"地形作用下,不同分区的动力结构、湍流特性、能量转化、能量耗散特征及其驱动机制不同。