单自由度体系在多次地震作用下的响应分析

基于opensees软件,通过数值模拟与国外学者的试验数据的比对,验证有限元模型的可靠性。对3个不同周期的模型进行多次地震分析和单一地震分析。结果显示,结构在多次地震作用下存在残余变形和振幅增大等现象。由于多次损伤的积累,多次地震分析下结构的抗震性能出现不同程度的变化,且与结构周期和地震波存在一定的关联性。     

单自由度体系非线性地震能量反应的计算

随着结构抗震理论的深入研究,目前对结构地震破坏比较一致的看法：基于最大位移反应首次超越和塑性累积损伤的双重破坏准则比较符合震害和试验实际.采用能量耗散来描述结构的塑性累积损伤,其形式简单、计算方便,又能够较好地反映地震动的强度、频谱特性,特别是强震持续时间对结构破坏的综合影响.建立了单自由度体系在地震作用下的能量反应公式,通过对结构地震反应能量的计算,综合考虑地震动三要素和结构自身动力特性,分析了地震总输入能受各种因素影响的变化规律及地震总输入能在滞回耗能和阻尼耗能之间分配受各因素影响的变化规律.     

基于Lyapunov稳定性的多自由度机械臂滑膜控制

针对轨迹跟踪控制,精确的动力学模型难以建立的问题,首先,分别采用基于估计模型和基于模型上界两种方法,设计出不同的滑膜控制器,并通过Lyapunov稳定性定理从理论上证明了控制器的稳定性。其次,结合两自由度平面机械臂给出了其动力学方程线性化的推导过程,最后,通过仿真实验验证了控制算法的有效性。     

水平采空区群离散多自由度动力响应模型

 为研究水平采空区群的水平动力响应规律,将其转化成有限多自由度离散振动体系,建立水平采空区群离散多自由度动力响应模型。考虑到围岩中的能量耗散(外部阻尼),引入耗损因子p,对动力响应模型进行修正。通过单层水平采空区群间柱爆破及多层水平采空区群顶板矿震2种工况,利用数值模拟对动力响应修正模型的合理性进行验证,并与未修正模型进行对比分析。结果表明,未修正模型和修正模型均能较好地对瞬时性和持续性动荷载做出响应;耗损因子p的取值主要取决于岩体内能量的传递路径和传递距离,单层与多层水平采空区群的赋存条件对耗损因子p的取值影响不明显;修正模型较未修正模型能更好地拟合数值模拟结果,一定程度上揭示了水平采空区群的动力响应规律,为水平采空区群的水平动力响应分析提供了一种新的有效途径。     

防冲吸能锚杆(索)的静动态力学特性与现场试验研究

针对冲击危险巷道锚杆支护结构破坏特征及冲击载荷对锚杆–围岩支护系统的特殊要求,设计研发了新型防冲吸能锚杆(索)。基于塑性弯曲理论分析了吸能锚杆(索)的吸能原理,利用自主设计的静–动加载试验系统,进行吸能锚杆(索)的静力拉伸试验与冲击拉伸试验。结果表明:吸能锚杆(索)在拉伸过程中六角管衬里被挤压变形,同时给摩擦圆柱提供滑移阻力,六角管的管壁厚度、套筒内径及摩擦圆柱直径三者的装配参数对吸能阻力具有重要影响;无论是静力拉伸还是冲击拉伸,吸能锚杆(索)的轴力–位移曲线均存在轴力初始增长、轴力平稳和轴力突增—平稳3个阶段;在轴力平稳阶段内锚杆杆体基本处于弹性状态,摩擦滑移结束后,锚杆杆体开始受力屈服;吸能结构在吸收能量的同时很好的延迟或减缓了锚杆杆体受力屈服。与普通锚杆相比,吸能锚杆(索)具有良好的"自保护性"与"冲击适应性"。现场试验表明,吸能锚杆(索)能够有效削弱冲击能对巷道围岩的作用。     

确定结构体系振动自由度的实用方法

通过对几种特殊结构进行适当处理,得到了相应的铰接链杆体系,从而可运用换铰法确定结构体系的振动自由度,扩大了换铰法的适用范围。     

基于二自由度机械式陀螺仪的稳态ATP系统研究

介绍了大气激光通信优点,以及捕获、跟踪、瞄准(ATP)关键技术。并对二自由度机械式陀螺仪系统进行分析,运用拉氏变换,得到转动的角度与转动惯量、外力矩、角动量的关系。设计出一种具有稳态功能的ATP系统,平台受抖动或冲击时,偏角小,接收信号光光轴几乎不变,适用于稳定性差工作平台。     

基于概率的单自由度体系震后残余变形计算

准确预测结构的震后残余变形,对于结构震后性能控制及建立考虑可修复性的抗震设计方法具有重要意义。通过对不同参数的双线性单自由度（SDOF）体系分别在100条标准地震动输入下弹塑性地震反应的统计分析,研究了模型参数和地震动不确定性对SDOF体系残余变形和最大弹塑性变形的影响;建立了双线性SDOF体系震后残余变形的概率计算模型。结果表明：不同地震动输入下SDOF体系的残余变形与最大弹塑性变形之比（dR/dm）存在明显的离散性,且离散程度与结构的刚度比、自振周期、相对屈服荷载系数及峰值地面加速度相关;dR/dm的统计分布规律服从对数正态分布,基于该分布函数建立的计算模型可对给定超越概率条件和地震水平下SDOF体系的震后残余变形进行预测。通过典型算例分析认为,可以采用所建议的模型进行SDOF体系震后残余变形分析及可修复性评估。     

Analysis on energy saving potential of integrated supermarket HVAC and refrigeration systems using multiple subcoolers

The paper presents a model-based analysis on the energy saving potential of supermarket HVAC (heating, ventilating, and air-conditioning) and refrigeration systems using multiple subcoolers among the high-temperature HVAC system, the medium-temperature refrigeration system, and the low-temperature refrigeration system. The principle of energy reduction is to have the higher COP (coefficient of performance) system generate more cooling capacity to increase the cooling capacity or reduce the power consumption of the lower COP system. The subcooler could be placed between the medium-temperature and low-temperature systems, between the high-temperature and medium-temperature systems, and between the high-temperature and low-temperature systems. All integration scenarios of adding one, two and three subcoolers have been investigated. The energy saving potential varies with the load ratio between high-, medium- and low-temperature systems, COP of three systems, and the “on-off” duty time of HVAC system. The optimal sequence of adding subcoolers is also proposed.     

Hilbert变换在SDOF线性滞回阻尼中的应用

线性滞回阻尼的恢复力大小有着与变形频率无关的特性 .考察了实值位移 Kelvin模型和复值位移 Kelvin模型 .借助 Hilbert变换 ,给出了线性滞回阻尼在单自由度结构体系下的时域表达法和频域表达法 .通过两个实际算例说明 Hilbert变换在分析具有滞回阻尼的线性结构时是很有效的 .     

Shell element of relative degree of freedom and its application on buckling analysis of thin-walled structures

Shell element of relative degrees of freedom (SERDF) is a special transformation of solid element. It can be used in finite element (FE) analysis of both thin and thick shell structures and the formulation is simpler than normal shell elements. Introduction of additional internal degrees of freedom will improve the calculation precision.FE formulation of SERDF in the buckling analysis is derived in this article. Different measures of tackling additional internal degrees of freedom for different kinds of buckling problems and different stages of numerical analysis are presented. Some numerical examples are given to illustrate the validity of this element and the method.     

含面内转角自由度的四结点四边形单元

利用十二结点等参数单元的形函数，推导含转角自由度的四结点四边形膜元的单元刚度矩阵，该单元能直接与每个结点具有六个自由度的空间梁柱单元相联结，能有效地解决工程实际问题。     

钢结构雨篷静力动力分析

通过某具体工程,利用ANSYS研究了静、动荷载作用下钢结构雨篷的力学性能,基于这种结构的非线性特征,并且考虑风与结构的耦合作用,对结构的选型、网格的划分及节点构造设计等问题进行了其强度、变形及稳定性分析,以推动钢结构雨篷的发展。     

梯形钢屋架静动力分析

在ANSYS环境下采用弹性分析建立有限元模型对屋架进行静力和水平地震波作用分析，对其在静力作用下进行了内力及变形的分析，同时，对其在水平地震波作用下的最大位移进行了分析并得出一定的结论。     

海洋平台结构静动力分析

从波浪荷载周期与平台自振周期的关系出发，对海洋平台结构所遭受的波浪荷载进行了分析，结合静力计算和动力计算，提出如何使用这两种方法来对海洋平台进行结构分析，从而确保结构安全。     

某立交匝道检测实验研究

为摸清某匝道的受力行为，基于通用有限元程序软件进行理论分析，同时进行静动载检测试验，检测实验结果有助于了解此类桥梁结构的受力性能。     

石川河大桥静动载试验分析

结合石川河大桥工程实例,介绍了荷载试验的测点布置,讲述了荷载试验的加载工况及加载车辆,分析研究了静载试验结果及动载试验结果,为评价桥梁的承载力提供了依据。     

Stochastic seismic analysis of multidegree of freedom systems

A unconditionally stable step-by-step procedure is proposed to evaluate the mean square response of a linear system with several degrees of freedom, subjected to earthquake ground motion.A non-stationary modulated random process, obtained as the product of a deterministic time envelope function and a stationary noise, is used to simulate earthquake acceleration. The accuracy of the procedure and its extension to nonlinear systems are discussed.Numerical examples are given for a hysteretic system, a duffing oscillator and a linear system with several degrees of freedom.     

Static and dynamic behaviour of shallow spherical shells on winkler foundation

Large deflection static analysis of shallow spherical shells on Winkler foundation is made, using Berger's and Modified Berger's methods. Small amplitude free vibration analysis of shallow spherical shells on Winkler foundation is carried out various methods. While Modified Berger's method gives better results for static analysis, the original Berger's approach is found to give good results for dynamic analysis     

Quantifying panel zone effect on deflection amplification factor

Drift is a dominant feature in tall‐building design and can dictate the selection of structural systems. Because a reliable estimate of actual drifts is crucial for controlling structural damage, estimating drift considering intricate details seems noteworthy. In order to estimate story drifts during massive quakes, seismic design provisions generally specify a deflection amplification factor (C_d) to amplify elastic design drifts. In most of these codes, the amount of C_d is calculated from line‐element models without considering panel zone effects, despite the panel zone intensifying the story drift considerably. Therefore, the effect of panel zone on the story drift and C_d has been investigated in the current paper. Because C_d is independent of the number of stories, 4‐story frames, as benchmarks for special steel moment frames, with different thicknesses of the panel zone, are used. The effect of panel zone is provided as a correction factor for C_d. The results show that the panel zone should be considered in the analytical models; otherwise, the story drift will be underestimated up to 35%. Finally, a relation has been derived to consider panel zone effects on C_d, as a function of the panel zone thickness.