武汉砂土动剪切模量与阻尼比的试验研究

以武汉地铁4号线二期工程越江段饱和砂土为研究对象,通过室内GDS动力三轴试验,较为系统地研究了在单向循环荷载作用下砂土的动剪切模量和阻尼比规律特性及其影响因素。试验结果表明:动剪切模量、阻尼比与动剪应变的关系可以用Hardin-Drnevich双曲线模型进行描述;动剪切模量随动应变的增大而减小,随围压和固结比的增大而增大,而阻尼比的变化规律与动剪切模量相反。从而为工程建筑物的抗震设计提供了重要依据。     

沙漠化土地振子模型研究——混沌振动在沙漠化防治中的应用

将沙漠化的土地系统模拟为振子系统,在对Duffing方程讨论基础上,分析了这一特殊振子的结构组成是造成生态系统脆弱的根本原因,并依据混沌振动规律提出了防治沙漠化的步骤和方法。     

Efficient methods for solving water flow in variably saturated soils under prescribed flux infiltration

The non-linear solvers in numerical solutions of water flow in variably saturated soils are prone to convergence difficulties. Many aspects can give rise to such difficulties and in this paper we address the gravity term and the prescribed-flux boundary in the Picard iteration. The problem of the gravity term in the Picard iteration is iteration-to-iteration oscillation as the gravity term is treated, by analogy with the time-step advance technique, ‘explicitly’ in the iteration. The proposed method for the gravity term is an improvement of the ‘implicit’ approach of Zhang and Ewen [Water Resour. Res. 36 (2000) 2777] by extending it to heterogeneous soil and approximating the inter-nodal hydraulic conductivity in the diffusive term and the gravity term with the same scheme. The prescribed-flux boundary in traditional methods also gives rise to iteration-to-iteration oscillation because there is no feedback to the flux in the solution at the new iteration. To reduce such oscillation, a new method is proposed to provide such a feedback to the flux. Comparison with traditional Picard and Newton iteration methods for a wide range of problems show that a combination of these two proposed methods greatly improves the stability and consequently the computational efficiency, making the use of small time step and/or under-relaxation solely for convergence unnecessary.     

地震前兆场的演化和能量非线性聚集的关系

运用非均匀介质中“非线性振动的局域能量聚集”过程,模拟唐山７．８级和大同６．１级地震的前兆场演化,发现地震孕育过程中出现的诸多前兆特征与地壳内构造能量的非线性聚集有关。     

导航电子地图增量更新服务及关键技术研究

以移动通讯数据传输技术、网络技术和时态数据库技术为基础,构建了导航地理信息的变化发现、分析甄别、采集、加工、处理、存储和发布服务一体化的增量式更新服务模式、技术、软件、质检和标准体系,论述了多源数据融合、时空模型及空间关系的动态实时维护、多尺度增量式导航电子地图综合处理、路径规划和质检方法等关键性技术,实现了导航电子地图近实时更新服务。     

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内潮动力机制的数值研究

结合南沙群岛海域出现的内潮现象 ,利用一个两层数值模式 ,通过数值试验来探讨潮汐性质、水体的层结程度、跃层所在的深度、风应力等因子对陆架坡折处内潮特性的影响 ,结果表明 :内潮的波动周期只与海区的潮汐性质有关 ;风应力、非线性效应以及正压潮源地的深度等都可改变内潮的波动振幅 ;内潮的波动振幅随海区的水体层结程度及温跃层所在的深度不同而改变     

沿岸上升流和沿岸急流的一个半解析理论

在考虑了陆架地形后，在垂直海岸的x z剖面上 ，对Boussinesq流体的非线性海洋运动方程求得了总动量守恒、温度守恒和位势涡度守恒的 普 适形式，进而得到流函数所满足的椭圆型二阶偏微分方程，在给定流体沿地形运动的条件下 ，算出问题的解. 计算结果表明，沿岸可以出现上升流也可以出现下沉流，它依赖于海洋的 大尺度背景条件. 计算所得的上升流、沿岸急流、温度的锋区结构与一些观测事实接近.     

Nonlinear dynamic tests of a reinforced concrete frame building at different damage levels

This paper discusses the dynamic tests of a two-story infilled reinforced concrete (RC) frame building using an eccentric-mass shaker. The building, located in El Centro, CA, was substantially damaged prior to the tests due to the seismic activity in the area. During the testing sequence, five infill walls were removed to introduce additional damage states and to investigate the changes in the dynamic properties and the nonlinear response of the building to the induced excitations. The accelerations and displacements of the structure under the forced and ambient vibrations were recorded through an array of sensors, while lidar scans were obtained to document the damage. The test data provide insight into the nonlinear response of an actual building and the change of its resonant frequencies and operational shapes due to varying damage levels and changes of the excitation amplitude, frequency, and orientation.     

摩擦与粘性流体耗能器串联体系动力分析

采用粘性屈服模型来模拟摩擦耗能器的力－速度关系，建立了摩擦与粘性流体耗能器串联耗能体系的动力分析方法．为考虑框架杆件和支撑材料的几何非线性，采用增量型Ｒｏｓｅｎｂｒｏｃｋ二级三阶半隐式Ｒｕｎｇｅ－Ｋｕｔｔａ法求解动力方程．比较了仅有摩擦耗能器体系与串联组合耗能体系的减振效果，分析了粘性流体耗能器参数对组合耗能体系减振效果的影响。