附设黏滞阻尼器的传统风格建筑混凝土梁-柱节点动力循环荷载累积损伤分析

为研究附设黏滞阻尼器的传统风格建筑混凝土梁-柱节点地震损伤演化规律,进行6个该类型构件的动力荷载试验,并分别采用位移型、能量型及位移-能量混合型损伤模型对其进行全过程评价,采用Park-Ang模型分析试件黏滞阻尼器型号、试件类型等因素对混凝土传统风格建筑梁柱节点损伤行为的影响。研究结果表明：附设黏滞阻尼器可显著提升传统风格建筑节点的承载能力、延性性能及耗能能力,结构的抗震性能得到较大幅度的提升;Park-Ang损伤模型与Banon损伤模型适用于传统风格建筑节点损伤演化规律的描述,建议对该类型节点的损伤规律表征选用该损伤模型。黏滞阻尼器型号可在一定程度上影响传统风格建筑的损伤演化发展;设计阻尼力大的试件虽然延性有所提高,但受荷过程中累积损伤也较大。     

Optimal design of supplemental viscous dampers for irregular shear‐frames in the presence of yielding

A methodology for the optimal design of supplemental viscous dampers for regular as well as irregular yielding shear‐frames is presented. It addresses the problem of minimizing the added damping subject to a constraint on an energy‐based global damage index (GDI) for an ensemble of realistic ground motion records. The applicability of the methodology for irregular structures is achieved by choosing an appropriate GDI. For a particular choice of the parameters comprising the GDI, a design for the elastic behavior of the frame or equal damage for all stories is achieved. The use of a gradient‐based optimization algorithm for the solution of the optimization problem is enabled by first deriving an expression for the gradient of the constraint. The optimization process is started for one ‘active’ ground motion record which is efficiently selected from the given ensemble. If the resulting optimal design fails to satisfy the constraints for other records from the original ensemble, additional ground motions (loading conditions) are added one by one to the ‘active’ set until the optimum is reached. Two examples for the optimal designs of supplemental dampers are given: a 2‐story shear frame with varying strength distribution and a 10‐story shear frame. The 2‐story shear frame is designed for one given ground motion whereas the 10‐story frame is designed for an ensemble of twenty ground motions. Copyright © 2005 John Wiley & Sons, Ltd.     

Viscosity—The weak link between Darcy's law and Richards' capillary flow

Preferential flow, a term that includes macropore flow, non‐equilibrium flow, and finger flow, stands in well known conflict with Richards' ( 1931 ) capillary flow. Acoustic velocity experiments demonstrate that preferential flow moves independently from, faster than, and before capillary flow during gravity‐driven infiltration. Viscous flow in permeable media is briefly introduced to the point where Richards' ( 1931 ) particular treatment of viscosity turns out as the hydro‐mechanical bifurcation from general laminar flow. Preferential flow is expected during significant infiltration, however, spatio‐temporarily limited according to the viscous‐flow regime. Two ways of delineating capillary flow from viscous flow reveal minimum path widths of preferential flow in the range of about 20 μm.     

油缸间隙式粘滞阻尼器理论与性能试验

本文首先研究了双出杆油缸间隙式粘滞阻尼器的构造,讨论了不同类型粘滞流体的特性;;然后,在幂律流体本构关系的基础上,建立了粘滞阻尼器的阻尼力计算模型;;最后,设计制作了两个粘滞阻尼器,进行了详细的性能试验,通过试验结果的统计分析,得到了阻尼力计算模型的幂指数。     

粘性泥石流体的应力应变特性和流速参数的确定

文章从粘性泥石流体的组成，应力应变特性和减阻作用的观测试验入手，揭示了粘性泥石流体运动的阻力特性，探讨了粘性泥石流流速公式中的曼宁糙率系数的表征。粘性泥石流体运动的阻力特性主要与沟槽特征以及泥深和粘附层流变特性有关。根据高、低不同阻力的粘性泥石流浆体的泥砂比，浆体介质的流变参数（ηp、τBf）和体积浓度（Cvf)，可获得不同阻力介质状态下统一的阻力糙率系数与它们的相关式，以此来确定曼宁糙率系数。     

Bianchi Type-V Bulk Viscous Fluid String Dust Cosmological Model In General Relativity

Bianchi Type-V bulk viscous fluid string dust cosmological model in General Relativity is investigated. It has been shown that if coefficient of bulk viscosity (ζ) is inversely proportional to the expansion (θ) in the model then string cosmological model for Bianchi Type-V space-time is possible. In absence of bulk viscosity (ζ), i.e. when ζ → 0, then there is no string cosmological model for Bianchi Type-V space-time. The physical and geometrical aspects of the model are also discussed.     

Direct displacement-based design for seismic retrofit of existing buildings using nonlinear viscous dampers

This paper presents a direct displacement-based design procedure for seismic retrofit of existing buildings using nonlinear viscous dampers according to equivalent linear systems. Unlike conventional methods, the equivalent linear viscous damping provided by the nonlinear viscous dampers is derived based on the assumption that the average energy dissipated between the linear and the nonlinear viscous dampers is equal. Also, the equivalent period and viscous damping for the equivalent linear systems which are used for representing the behavior of bare frames (the buildings without dampers) are derived from the concept of average storage energy and average dissipated energy, respectively. It is shown from nonlinear time-history analyses that the nonlinear action of the retrofitted structures can be reasonably captured by the presented direct displacement-based procedure.     

造山带下岩石圈地幔小尺度减薄的动力学成因

地质与地球物理观测数据表明青藏高原、安第斯山、以及帕米尔等典型造山高原之下均有明显的岩石圈地幔小尺度/分段式减薄现象.这些小尺度岩石圈减薄难以用经典的拆沉或对流减薄理论来解释,一方面,拆沉预示大尺度岩石圈地幔的剥离过程,而对流减薄则在黏度相对低的地幔岩石圈中发生,其主要以小尺度的局部增厚触发并仅减薄地幔岩石圈的底部区域.另一方面,拆沉或对流减薄模型都预测造山带尺度的地幔岩石圈拆离,都假设造山带岩石圈横向均一,然而实际的造山带岩石圈往往由多个不同的地块构成,块体之间岩性、物性、流变结构可能大有差别,即横向不均一性.这些造山带岩石圈地幔的横向不均一性,能否有效解释观测到的局部小尺度减薄现象？为此,我们构建了一系列高精度动力学数值模型,系统模拟了碰撞造山过程中岩石圈地幔的形变和不稳定性.结果表明,在塑性屈服强度很低的情况下,横向不均一的造山带岩石圈有发生分段式/小尺度减薄的可能性;其主要机理是由位错蠕变与强塑性作用所导致的应变集中使得地块间及壳幔间耦合弱化,从而使得较弱地块的岩石圈地幔在增厚时由于重力不稳定性而产生局部剥离,进而诱发小尺度软流圈上涌.模拟结果可以良好地解释发生在青藏高原东北缘、安第斯中部高原、以及帕米尔高原之下岩石圈的局部小尺度/分段式减薄现象.

     

Numerical Simulation of Viscous Flow Around a Rolling Cylinder with Ship-Like Section

Two-dimensional unsteady incompressible viscous flow around a rolling cylinder with ship-like section is numerically simulated by employing the computational scheme previously developed by the authors, in which the continuity and momentum equations are satisfied simultaneously at each time step for oscillating flow. The numerical results show that the motion of vortices around a rolling ship hull is cyclical. It is found that the location of the vortices is very similar to the existing experimental result. Using these simulation results, we can calculate the roll damping of ships including viscous effects.