钢筋混凝土框支剪力墙结构抗震设计

本文根据R.C抗震延性结构确定性设计的基本原理,研究了R,C框支剪力墙结构的抗震设计问题,分析了影响结构抗震性能的主要因素,提出改善结构抗震性能的关键在于挖掘结构本身潜力和采取必要的构造措施。根据这一观点,给出了R.C框支剪力墙结构的抗震设计方法。试验分析表明:采用这种设计方法,并且在结构的潜在耗能部位,嵌入“人工塑性铰”,可以避免结构由于底部框架刚度、强度不足发生破坏,结构延性较大。通过设计,控制结构出现最佳耗能机构,改善R.C.框支剪力墙结构的抗震性能。     

流体运动估计光流算法研究综述

对流体图像序列进行运动分析一直是流体力学、医学和计算机视觉等领域的重要研究课题。从图像对中提取的密集精确的速度矢量场能够为许多领域提供有价值的信息,基于光流法的流体运动估计技术因其独特的优势成为一个有前途的方向。光流法可以获得具有较高分辨率的密集速度矢量场,在小尺度精细结构的测量上有所改进,弥补了基于相关分析法的粒子图像测速技术的不足。此外,光流方法还可以方便的引入各种物理约束,获得较为符合流体运动特性的运动估计结果。为了全面反映基于光流法的流体运动估计算法的研究进展,本文在广泛调研相关文献的基础上,对国内外具有代表性的论文进行了系统阐述。首先介绍了光流法的基本原理,然后将现有算法按照要解决的突出问题进行分类：结合流体力学知识的能量最小化函数,提高对光照变化的鲁棒性,大位移估计和消除异常值。对每类方法,从问题解决过程的角度予以介绍,分析了各类突出问题中现有算法的特点和局限性。最后,总结分析了流体运动估计技术当前面临的问题和挑战,并对未来基于光流法的运动估计算法的研究方向和研究重点进行了展望。     

索承式桥梁吊索钢丝腐蚀疲劳寿命评估

根据吊索镀锌钢丝腐蚀疲劳破坏特点,把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段,建立各阶段时间表达式,得到镀锌钢丝疲劳寿命表达式,提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响,研究结果表明：吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成,为了准确地评估吊索腐蚀疲劳寿命,需要掌握大桥的运营环境和交通荷载。     

Modeling and Simulation on the Underwater Trajectory of Non-Powered Vehicle Discharged from the Broadside

In order to study the underwater trajectory of the non-powered vehicle discharged from the broadside of the underwater platform, the simulation on the ascent process of non-powered vehicle was realized based on the mathematical model including the movement of the vehicle on the slope plate and in the seawater, the air chamber underwater working process etc. The simulation results show that the outlet speed and attitude of the vehicle meet the requirements of missile launching, the non-powered vehicle discharged from the broadside of the underwater platform is feasible. The simulation results with varying parameters show that the negative buoyancy of the vehicle imposes great impacts on the security of its discharge and the floating process, and the vehicle discharge depth is proportional to the floating time. The models and simulation result can be used in further research on the broadside discharging technology of the underwater platform.     

Trajectory Simulation for Underwater Vehicle with Power-Lunched

The motion of combustion gas bubble produced by underwater ignition was developed based on Rayleigh-Plesset equation. Combining the bubble motion equation with the underwater launched vehicle motion equation in the longitudinal plane, a trajectory simulation model with power-launched was established. The hydrodynamic characteristics of underwater ignition at different depths and the trajectory analysis of the underwater vehicle with power-launched were given by simulation. The simulation results have a good agreement with experimental results, and show that the thrust peak caused by underwater ignition and the stable thrust both decrease slightly with the increase of the water depth, and the thrust peak will decline obviously by enlarging the initial radius of gas bubble; the thrust peak generated at the instant of ignition and the low-frequency oscillation of the stable thrust have no significant influence on the trajectory of underwater vehicle.     

竹纤维混凝土结构加固方法的分析

混凝土加固技术作为新兴技术之一,在实际工程中得到广泛应用,取得良好的效果与广泛的应用场合。本文在结合现有几种混凝土加固技术的前提下,着重介绍了竹纤维混凝土的基本情况与力学性能,并对这一材料的发展状况和应用前景作出讨论。举例论证了竹纤维混凝土在实际运用中的优势,为未来该材料进一步的发展提供理论基础和分析。     

“卓越计划”引领下结构力学课程教学改革与实践

在阐述结构力学课程在卓越土木工程师培养中的重要地位的基础上,指出了以往结构力学教学中存在的不足,提出了加强理论与实践联系、加强定性能力的培养、加强对计算结果的研判、加强教师队伍建设等改进措施,以期提高结构力学课程教与学的质量,为同类学校提供一些借鉴。     

中部铰支加固的细长压杆稳定性研究

基于挠曲线近似微分方程,对中部任意位置增加一个铰支的细长压杆,由初参数法建立了统一的变形方程和静力平衡方程。分9种常见情况,由求解各自的8个初参数的变形边界条件和静力约束条件,导出求解其临界压力的特征方程。借助计算软件,求得了长度因数的数值解,并确定了中部支承的合理位置及最小长度因数。     

侧爆作用下锚固洞室破坏形式及机理研究

为了进一步提高锚固洞室在侧爆作用下的抗爆能力,利用数值分析软件LS-DYNA3D程序,研究了在侧爆作用下的锚固洞室的破坏形式及机理.数值分析结果表明:压应力波一开始是以球形向四周传播的,当压应力波碰到洞室壁时,会在洞室壁表面产生拉应力波,并以椭圆形式向反向传播;在应力波整个传播过程中,由于反射拉伸可能会在洞室锚固区和非锚固区先后产生二次拉伸破坏,最后可能会由于洞室反射的拉伸波和地面反射拉伸波相遇共同作用,在离地面比较浅的地方产生拉伸破坏区.     

Drag reduction of aqueous suspensions of fine solid matter in pipe flows

It is well known that drag reduction properties of polymer solutions in pipe flows are classified into two categories, based on the relationship between the friction factor and the Reynolds number. The degree of drag reduction either increases with an increase in the Reynolds number or is independent of the Reynolds number. In the latter case, the drag reduction behavior is referred to as type B behavior. In this study, the pressure losses of aqueous suspensions of biofibers and graphene oxide flat particles in pipe flows were measured to clarify the effect of the shape of suspended fine solid matter on the friction factor. The experimental results demonstrated that the behavior of the friction factor corresponded with the type B behavior of drag reduction. The mean velocity profile in the range of the turbulent flow was also estimated from the friction factor data.