大跨钢箱梁悬索桥地震响应有限元分析

根据某大跨钢箱梁悬索桥的设计图纸,采用ANSYS建立其有限元模型,采用壳单元对主梁进行模拟.通过不断调试找出最佳的主缆初始应力,完成悬索桥的初始找形分析.对悬索桥进行预应力模态分析,采用瑞利阻尼理论,通过悬索桥有限元模型的前2阶圆频率计算模型的质量阻尼和刚度阻尼.采用动力时程分析法对悬索桥进行地震响应有限元分析.结果表明:横桥向位移的最大峰值由横桥向地震波输入决定,纵桥向位移的最大峰值以及竖桥向位移的最大峰值主要由重力载荷工况决定,地震载荷工况对其贡献非常小.     

悬索桥主缆初应力对桥梁动力特性的影响

为掌握主缆初应力对桥梁动力特性的影响,以悬索桥为例,采用静力非线性分析方法计算应力变化过程中悬索桥的跨中挠度、缆索轴力及加劲梁的轴力变化;将得到的内力作为结构的预加应力进行有预应力的模态分析. 应用ANSYS软件进行分析,其中有限元建模时采用4种单元类型:空间梁单元BEAM4用于模拟加劲梁和塔;空间杆单元LINK10用于模拟主缆及吊杆;通过设定BEAM4和LINK10单元初应变进行有预应力的模态分析;采用MASS21单元模拟横隔板、吊杆锚固装置和桥面上的栏杆,并分别考虑质量和质量惯性矩的作用. 分析表明,悬索桥主梁竖弯振动频率受主缆初应力的影响较大,而侧弯振动频率和扭转振动频率受此影响较小. 该结果为同类桥梁的动力特性分析提供参考.     

浮筒转塔式系泊系统中的动态管缆数值分析

借助有限元法,结合非线性时域分析,对浮筒转塔式系泊(Buoyant Turret Mooring,BTM)系统与FPSO脱离前后分别采取不同的分析策略,解决其柔性立管、动态脐带缆和动态电缆(合称动态管缆)的设计分析工作量大以及所面临的高度非线性和强耦合等难题.以我国南海某BTM系统的动态管缆的分析为例,借助专业立管分析软件Orcaflex展示该类系统的数值建模和分析技术,并通过极值和疲劳的分析与评价阐述此类工程设计的技术特点.     

不同因素对钢框架内承载性能的影响模型仿真

设计5个小跨高比钢框架内填混凝土剪力墙试件,采用ABAQUS有限元软件模拟分析低周反复加载下,不同跨高比、配钢率等因素对试件承载性能的影响,统计分析试件应力云图、骨架曲线、耗能能力等指标.实验结果表明,CBB1试件的危险应力区域最大,试件最容易破坏.CBB5试件危险应力区域最小,最不容易被破坏;试件跨高比和配钢率越高,...     

单侧主缆刚度损伤悬索桥的模态分析及1∶1内共振

悬索桥缆索在长期服役状态下损伤很难避免,单侧主缆刚度损伤会使系统出现主梁竖弯与扭转自由度间的耦合,这可能会进一步对悬索桥的模态和大振幅下的非线性响应造成影响.为此,建立了考虑单侧主缆刚度受损的七自由度悬索桥横截面模型,模态分析发现单侧主缆刚度损伤会使得系统前两阶固有频率曲线由交叉变为跃迁,导致两个本身相互独立的模态发生耦合.以此为基础,考虑悬索桥主缆刚度有损伤和未损伤两种工况,运用拓展的增量谐波平衡法(EIHB)计算系统在内共振条件下的非线性振动.研究结果表明：单侧主缆刚度有损伤的悬索桥在外部简谐激励下发生1:1内共振,系统能量表现出明显的转移现象;竖向和扭转简谐激励下,有损伤的悬索桥较未损伤工况响应幅值有所减小,但出现了两个共振响应峰值,对激励频率更为敏感.数值结果与利用Runge-Kutta法计算得到的结果吻合一致,验证了EIHB法的准确性.     

基于动态模拟的危险与可操作性分析在精馏塔中的应用

危险与可操作性分析是化工领域中广泛应用的安全分析的有效方法,近年来其定量化研究已经成为一种趋势.为了实现定量化的危险与可操作性分析,本文提出了基于动态模拟的危险与可操作性分析的新型方法,即在传统的危险与可操作性分析的基础上引入了动态模拟模型,利用动态模拟的定量化弥补传统危险与可操作性分析定量化不足的缺陷.通过对动态模拟模型中操作参数进行不同程度的拉偏可以方便地模拟危险与可操作性分析中引导词与工艺参数组成的偏差,模拟的结果变化就是偏差对系统所造成的影响,以此实现危险与可操作性分析的定量化推理.本文利用对一个萃取精馏塔的冷凝能力缺失和安全阀失效问题阐述了基于动态模拟的危险与可操作性分析方法的新型研究方法.最后,根据案例分析总结了这种新型分析方法的优点,并且研究证明其为一种行之有效且非常有潜力的分析方法.     

基于虚拟样机技术的发动机建模与扭振分析

在建立动态发动机刚性模型的基础上,结合有限元软件ANSYS,计算出曲轴各阶模态的频率,从而得到含柔性曲轴的动态发动机模型;然后对该模型进行动态仿真,计算出发动机的扭振激振力矩;再对激振力矩进行离散傅立叶展变换,分析各谐次所对应的激振力矩的谐值;最后对发动机模型在共振工况进行仿真分析,求得危险轴段处的扭转应力,分析其安全性能.所提供的这种基于虚拟样机技术的发动机曲轴系扭振分析方法为实际中发动机曲轴系扭振分析,提供了一定的参考依据.     

钢管脐带缆弯曲刚度有限元分析

为评价钢管脐带缆的弯曲性能,用ANSYS建立高效的钢管脐带缆三维有限元模型,采用梁单元模拟其中所有构件,在相互接触的构件之间设置线线接触模拟其相互作用,并采用库伦摩擦模拟构件间的摩擦行为.将弯曲刚度的分析结果与经典的理论分析结果进行对比,验证有限元模型的正确性.基于此模型,分析不同螺旋角度以及不同摩擦因数对脐带缆弯曲刚...     

跨介质飞行器弹道仿真分析

研究气/水跨介质飞行器的动态特性,跨介质飞行器是一种新型概念飞行器,为了了解跨介质飞行器的运动特点,提出建立了跨介质飞行器的运动数学模型,对弹道进行仿真研究.通过对跨介质飞行器的空间运动进行受力分析,进行跨介质飞行器三种典型弹道的仿真分析.仿真结果基本完成了跨介质飞行器起飞巡航弹道,贴水滑行弹道以及触水滑跳弹道三种典型弹道的仿真,而且由于跨介质飞行器的浸水深度较小,极大地降低了水阻力的影响,可以达到较高的航行速度,为气/水跨介质飞行研究提供了依据.     

基于数值模拟的钢管脐带缆安装挤压分析

针对钢管脐带缆安装铺设时张紧器挤压力的选择问题,建立钢管脐带缆二维有限元模型,在总挤压力一定时对比不同形式(两履带式、三履带式及四履带式)张紧器下脐带缆关键构件钢管内部应力状态及缆体截面变形情况,发现四履带式作用下的脐带缆不易破坏.探究安装过程中脐带缆在不同截面位置角情况下内部钢管的应力变化和变形,并基于最危险位置角求得脐带缆所能承受的最大挤压力.该分析方法和结果可为脐带缆安装的实际工程提供参考.     

动态海缆机械性能有限元分析

为探究动态海缆在剧烈交变环境载荷下的疲劳寿命,基于环境载荷响应,开展动态海缆系统的整体分析。基于有限元方法,研究海水中悬浮的动态海缆在服役过程中承受的极端载荷,分析破断力和侧压力工况,提取关键部位的应力、应变分布并进行校核。研究结果可为动态海缆材料选型、结构优化以及疲劳分析和测试提供理论依据。     

Control of dynamic microsystems

This paper formulates and solves control problems for nonlinear microsystems which comprise micro-electromechanical devices, micromachined transducers and microelectronics. We perform a consistent dynamic analysis and coherent designs with a minimum level of simplifications using high-fidelity mathematical models. The proposed methodology enables practical implementation for multi-input/multi-output systems due to overall conceptual consistency, design coherence, computational efficiency, algorithmic effectiveness and hardware simplicity. Various issues in nonlinear analysis and control are examined and experimentally verified substantiating design concepts for high-performance microsystems. The reported findings are demonstrated for a proof-of-concept closed-loop electrostatic microactuator.     

Path selection in disaster response management based on Q-learning

Suitable rescue path selection is very important to rescue lives and reduce the loss of disasters, and has been a key issue in the field of disaster response management. In this paper, we present a path selection algorithm based on Q-learning for disaster response applications. We assume that a rescue team is an agent, which is operating in a dynamic and dangerous environment and needs to find a safe and short path in the least time. We first propose a path selection model for disaster response management, and deduce that path selection based on our model is a Markov decision process. Then, we introduce Q-learning and design strategies for action selection and to avoid cyclic path. Finally, experimental results show that our algorithm can find a safe and short path in the dynamic and dangerous environment, which can provide a specific and significant reference for practical management in disaster response applications.     

Topology/shape optimisation of axisymmetric continuum structures – a metamorphic development approach

A novel topology/shape optimisation method for axisymmetric elastic solids, based on solid modeling and FE analysis, is presented. Optimal profiles of minimum-mass axisymmetric structures are sought by growing and degenerating simple initial structures subject to response constraints. The rates of the growth and degeneration are controlled based on the current objective and constraint functions of the optimisation problem under consideration. The optimal structures are developed metamorphically in specified infinite design domains using both quadrilateral and triangular axisymmetric finite elements that are ideally suited for modeling continua involving curved boundaries.The robustness of this fully automatic method is studied and validated with the first example of seeking the optimal shape of a centrally suspended axisymmetric object with minimum strain energy caused by self-weight. Then the method is applied to a practical industrial design problem: the design of a turbine disk. The variations of load and boundary conditions caused by shape change in these problems, including the gravitational and centrifugal loads, and temperature distribution are accommodated in the optimisation procedures. Thus, the design model closely resembles the real design problem. The results demonstrate the success of the method in generating optimal but realistic solutions to practical design problems.     

Nonlinear dynamic response structural optimization using equivalent static loads

It is well known that nonlinear dynamic response optimization using a conventional optimization algorithm is fairly difficult and expensive for the gradient or non-gradient based optimization methods because many nonlinear dynamic analyses are required. Therefore, it is quite difficult to find practical large scale examples with many design variables and constraints for nonlinear dynamic response structural optimization. The equivalent static loads (ESLs) method is newly proposed and applied to nonlinear dynamic response optimization. The equivalent static loads are defined as the linear static load sets which generate the same response field in linear static analysis as that from nonlinear dynamic analysis. The ESLs are made from the results of nonlinear dynamic analysis and used as external forces in linear static response optimization. Then the same response from nonlinear dynamic analysis can be considered throughout linear static response optimization. The updated design from linear response optimization is used again in nonlinear dynamic analysis and the process proceeds in a cyclic manner until the convergence criteria are satisfied. Several examples are solved to validate the method. The results are compared to those of the conventional method with sensitivity analysis using the finite difference method.     

A study of suspended roofs for near-source seismic motions

The non-linear behavior of multi-suspended roof systems for seismic loads is studied. The study is based on a formulation that can be easily employed for a preliminary design of multi-suspended roofs subjected to seismic loads. Specifically, applying Lagrange’s equations, the corresponding set of equations of motion for discrete models of multiple suspension roofs is obtained and numerical integration of the equations of motion is performed via the Runge–Kutta scheme. For representative realistic combinations of geometric, stiffness and damping parameters, a non-linear analysis is employed to study the behavior of suspended roofs for near-source and far-field seismic motions. The analysis demonstrates that: (i) code-specified design loads could dramatically underestimate the response of suspended roofs subjected to near-source ground motions and (ii) flexible roofing systems are greatly affected by near-source ground motions, a behavior that is not observed for stiff systems.