Longitudinal integral response deformation method for the seismic analysis of a tunnel structure

For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this paper.The determinations of the structural critical moments when maximal deformations and internal forces in the longitudinal direction occur are deduced as well.When applying the proposed method,the static analysis of the free-field computation model subjected to the least favorable free-field deformation at the tunnel buried depth is performed first to calculate the equivalent input seismic loads.Then,the equivalent input seismic loads are imposed on the integral tunnel-foundation computation model to conduct the static calculation.Afterwards,the critical longitudinal seismic responses of the tunnel are obtained.The applicability of the new method is verified by comparing the seismic responses of a shield tunnel structure in Beijing,determined by the proposed procedure and by a dynamic time-history analysis under a series of obliquely incident out-of-plane and in-plane waves.The results show that the proposed method has a clear concept with high accuracy and simple progress.Meanwhile,this method provides a feasible way to determine the critical moments of the longitudinal seismic responses of a tunnel structure.Therefore,the proposed method can be effectively applied to analyze the seismic response of a long-line underground structure subjected to non-uniform excitations.

Coseismic site response and slope instability using periodic boundary conditions in the material point method

This paper proposed the explicit generalized-a time scheme and periodic boundary conditions in the material point method(MPM)for the simulation of coseismic site response.The proposed boundary condition uses an intuitive particle-relocation algorithm ensuring material points always remain within the computational mesh.The explicit generalized-a time scheme was implemented in MPM to enable the damping of spurious high frequency oscillations.Firstly,the MPM was verified against finite element method(FEM).Secondly,ability of the MPM in capturing the analytical transfer function was investigated.Thirdly,a symmetric embankment was adopted to investigate the effects of ground motion arias intensity(I_(a)),geometry dimensions,and constitutive models.The results show that the larger the model size,the higher the crest runout and settlement for the same ground motion.When using a Mohr-Coulomb model,the crest runout increases with increasing I_(a).However,if the strain-softening law is activated,the results are less influenced by the ground motion.Finally,the MPM results were compared with the Newmark sliding block solution.The simplified analysis herein highlights the capabilities of MPM to capture the full deformation process for earthquake engineering applications,the importance of geometry characterization,and the selection of appropriate constitutive models when simulating coseismic site response and subsequent large deformations.

STOCHASTIC OPTIMAL CONTROL FOR THE RESPONSE OF QUASI NON-INTEGRABLE HAMILTONIAN SYSTEMS

A strategy is proposed based on the stochastic averaging method for quasi non- integrable Hamiltonian systems and the stochastic dynamical programming principle.The pro- posed strategy can be used to design nonlinear stochastic optimal control to minimize the response of quasi non-integrable Hamiltonian systems subject to Gaussian white noise excitation.By using the stochastic averaging method for quasi non-integrable Hamiltonian systems the equations of motion of a controlled quasi non-integrable Hamiltonian system is reduced to a one-dimensional av- eraged It stochastic differential equation.By using the stochastic dynamical programming princi- ple the dynamical programming equation for minimizing the response of the system is formulated. The optimal control law is derived from the dynamical programming equation and the bounded control constraints.The response of optimally controlled systems is predicted through solving the FPK equation associated with It stochastic differential equation.An example is worked out in detail to illustrate the application of the control strategy proposed.

Seismic Response of Submerged Floating Tunnel Tether

A mathematical equation for vibration of submerged floating tunnel tether under the effects of earthquake and parametric excitation is presented. Multi-step Galerkin method is used to simplify this equation and the fourth-order Runge-Kuta integration method is used for numerical analysis. Finally, vibration response of submerged floating tunnel tether subjected to earthquake and parametric excitation is analyzed in a few numerical examples. The results show that the vibration response of tether varies with the seismic wave type; the steady maximum mid-span displacement of tether subjected to seismic wave keeps constant when parametric resonance takes place; the transient maximum mid-span displacement of tether is related to the peak value of input seismic wave acceleration.

A COMBINED PARAMETRIC QUADRATIC PROGRAMMING AND PRECISE INTEGRATION METHOD BASED DYNAMIC ANALYSIS OF ELASTIC-PLASTIC HARDENING/SOFTENING PROBLEMS

The objective of the paper is to develop a new algorithm for numerical solution of dynamic elastic-plastic strain hardening/softening problems. The gradient dependent model is adopted in the numerical model to overcome the result mesh-sensitivity problem in the dynamic strain softening or strain localization analysis. The equations for the dynamic elastic-plastic problems are derived in terms of the parametric variational principle, which is valid for associated, non-associated and strain softening plastic constitutive models in the finite element analysis. The precise integration method, which has been widely used for discretization in time domain of the linear problems, is introduced for the solution of dynamic nonlinear equations. The new algorithm proposed is based on the combination of the parametric quadratic programming method and the precise integration method and has all the advantages in both of the algorithms. Results of numerical examples demonstrate not only the validity, but also the advantages of the algorithm proposed for the numerical solution of nonlinear dynamic problems.

Excited response of granular ores in vibrating field

The dynamical theory was utilized to probe into the law of the excited response of granular ores generated by the exciting action of exciter and the influence of wave propagation in vibrating field. The exciter with double axes was presented as an example, and the principle of exciter and its mathematical expression of the excitation force were given. The granular ores have viscidity and damping speciality, on the basis of which the motion equation of excited response of ores was established and the approximate expression of mode displacement by harmonic excitation and the steady effect solution of coordinate response were deduced. Utilizing the step by step integration method, the recursion relation matrix of displacement, velocity and acceleration of the excited response of ores were obtained, and the computational flow chart and a computational example were given. The results show that the excited response can change the dynamical character and the flowing characteristic of granular ores.

Transient stochastic response of quasi integerable Hamiltonian systems

The approximate transient response of quasi in- tegrable Hamiltonian systems under Gaussian white noise excitations is investigated. First, the averaged It6 equa- tions for independent motion integrals and the associated Fokker-Planck-Kolmogorov （FPK） equation governing the transient probability density of independent motion integrals of the system are derived by applying the stochastic averag- ing method for quasi integrable Hamiltonian systems. Then, approximate solution of the transient probability density of independent motion integrals is obtained by applying the Galerkin method to solve the FPK equation. The approxi- mate transient solution is expressed as a series in terms of properly selected base functions with time-dependent coeffi- cients. The transient probability densities of displacements and velocities can be derived from that of independent mo- tion integrals. Three examples are given to illustrate the ap- plication of the proposed procedure. It is shown that the re- suits for the three examples obtained by using the proposed procedure agree well with those from Monte Carlo simula- tion of the original systems.

基于组合赋权与灰云模型的综合能源系统需求响应效益评价

考虑到当前综合能源系统研究缺乏完善的需求响应量化评估方案,难以在优化运行层面综合评估需求响应效益这一问题,提出了一种基于改进AHP群决策—CRITIC组合赋权与灰云模型的综合能源系统需求响应效益评价方法。首先,从综合能效性、社会经济性和需求侧互动性三个维度构建了需求响应效益评价指标体系。其次,采用一致性和权重拟合性更优的指数标度法构造判断矩阵,降低赋值误差,并通过AHP群决策法确定主观权重,从而削弱主观极值偏差对权重的影响;在由CRITIC法确定客观权重后,基于最小欧氏距离建立组合权重模型,并通过非线性规划求取最优组合权重;针对评价等级信息的模糊性与隶属等级的随机性,采用正态灰云白化权模型确定指标分类等级与场景评分。最后,以北方某综合能源系统为例,根据用户参与需求响应方式设置了4种运行场景,分析了不同需求响应对系统运行的影响与作用,算例结果表明所提指标体系与评价方法科学有效。

考虑高阶振型效应的大跨度钢桁拱桥瑞利阻尼参数取值研究

为了解高阶振型效应对大跨度钢桁拱桥地震反应的影响机制,以及在采用直接积分法时构建合适的瑞利阻尼矩阵,以某490 m跨径钢桁拱桥为背景,采用SAP 2000软件建立全桥弹性动力计算模型。针对主拱圈上(下)弦杆轴力、弯矩,研究振型参与质量最大的7阶(第1、4、8、11、13、23、49阶)振型反应与总反应的占比关系,并对构建瑞利阻尼矩阵的特征频率选取方法展开研究。结果表明:主拱圈上、下弦杆拱脚区域的轴力主要由1阶振型(第1阶)控制,由拱脚向拱顶过渡,逐渐转变为由2~4阶振型控制,高阶振型效应显著;同一阶振型对主拱圈上、下弦杆轴力贡献率及分布规律的影响不同;对于复杂钢桁拱桥,采用振动方向上振型参与质量较大的2阶振型特征频率构建瑞利阻尼矩阵可能因高估了高阶振型阻尼比,导致除拱脚区域以外的拱圈弦杆杆件轴力计算结果偏小,结构偏于不安全;采用直接积分法对复杂钢桁拱桥进行地震反应分析时,建议选取多阶控制振型构建相应的瑞利阻尼工况,并对其计算结果取包络用于抗震设计。

磁浮管轨直线感应电机牵引悬浮协同优化设计

在磁浮管轨运输系统中,采用悬浮电磁铁与直线感应电机(linear induction motor,LIM)同平面安装方案,可有效减小盾构面积,降低建设成本;同时,LIM法向力能够提供辅助悬浮力,提高系统综合能效。围绕牵引力与法向力协同优化中建模求解误差大、优化复杂等问题,提出一种基于响应面法的一体化LIM优化设计方法。首先,确立牵引力及法向力设计目标,完成电机初始设计。其次,结合Box-Behnken试验设计法和方差分析法,分析电机参数对牵引力和法向力的影响规律,确定敏感参数集。再次,利用响应面法建立关于敏感参数的二阶代理模型,并通过了模型拟合度检验。在加工精度与电机饱和等约束下,通过二代非支配排序遗传算法对代理模型进行多目标寻优。最后,利用Maxwell软件对优化前后的电机进行时步有限元仿真。结果表明,在工频、额定电流15 A的工况下,初始电机的牵引力和法向力分别为305.9和-60.5 N,优化后为309.4和-309.3 N,优化后性能指标显著提升,设计误差分别为3.13%和3.10%,表明了协同优化设计方法切实有效。

移动光照下液晶弹性体固支梁的动态响应分析

液晶弹性体(LCE)梁在移动光照作用下会产生弯曲动态响应,为此建立LCE固支梁在移动光照下的动态模型,并推导出动态响应的控制方程。在此基础上,通过模态叠加法和Duhamel积分法获得LCE固支梁在移动光照下动态响应的解析解,并利用Matlab软件对模型进行编程进而分析物理参数对LCE固支梁动态响应的影响。结果表明:当移动光照的速度达到一阶临界速度时,固支梁跨中动态响应的振幅最大。此外,通过改变光照强度、LCE的材料收缩系数和阻尼系数等参数,可以有效调控动态响应。研究成果在软机器人、智能控制和能量转换等领域具有应用价值。

整体式弹性扶正器结构参数分析

随着钻井作业需求及技术的发展,作业深度越来越深,井下作业环境变的复杂多变,对弹性扶正器的性能提出了更高的要求。整体式弹性扶正器的核心部件——扶正器弓片的弹性性能是衡量整个扶正器性能的关键指标。弓片的复位力和其应变能密度是评估弓片弹性特性的重要参数,直接影响着扶正器的工作效率和可靠性。对建立的井眼-扶正器-套管有限元三维模型进行了分析;基于响应曲面法,研究并分析了扶正器的弓片弦长、壁厚、弓片宽度三个结构参数对扶正器复位力与应变能密度影响规律;通过试验验证了有限元分析的可靠性。研究结果表明:影响复位力的主次因素依次为壁厚、弓片宽度、弓片弦长;影响应变能密度的主次因素依次为弓片宽度、壁厚、弓片弦长。研究结果可为整体式弹性扶正器几何结构对复位力与应变能密度分析提供理论参考。

齿侧间隙非线性函数拟合阶次的选取研究

针对齿侧间隙非线性函数拟合阶次的选取问题,以斜齿轮传动系统为例,对齿轮系统进行了理论建模、仿真分析,并对实际齿轮系统进行了实验研究。首先,采用集中质量法建立了考虑轴向振动的齿轮非线性系统模型,并对数学模型进行了无量纲化,对齿侧间隙函数分别进行了无拟合、4阶拟合和8阶拟合处理;然后,采用Runge-Kutta数值积分法进行了数值仿真分析,得到了齿轮系统x、y、z三个方向的幅值-频率比响应曲线图,研究了拟合阶次对系统x、y、z三个方向动态特性的影响;最后,进行了齿轮系统动态测试,得到了齿轮系统x、y、z三个方向的振动响应图,根据仿真与实验结果得出了结论。研究结果表明:不同处理方式下的齿轮系统振动响应在z向的差异较大,拟合阶次的选取应重点考虑z向;在x、y方向,齿侧间隙非线性4阶拟合函数会提前改变齿面接触状态且共振振幅分别增大1倍和1/3倍;对于多间隙的齿轮非线性系统,对齿侧间隙进行无拟合处理,可能导致计算困难和结果不准确;在固有频率附近,对齿侧间隙进行4阶拟合处理能够最大程度弥补其他非线性因素带来的影响;在其他频率范围,对齿侧间隙进行8阶拟合处理会更接近真实齿轮系统。齿侧间隙非线性函数的拟合处理在提高了计算效率的同时,也提高了模型的准确性。

近海深水区混凝土半潜型浮式风机一体化计算与耦合动力特性分析

[目的]文章旨在探索10 MW级半潜型浮式风机的一体化计算方法并分析其在40~50 m近海深水区的耦合动力响应特性。[方法]以10 MW混凝土半潜型浮式风机为例,构建一体化时域数值计算模型,统计分析其额定发电和极端工况下的平台动力响应和系泊张力特征。[结果]平台水平运动主要受波浪荷载、风荷载和系泊刚度特性的影响,最大水平运动和系泊张力发生在生存工况,垂向运动主要受波浪荷载影响,摇摆运动的均值主要受风荷载影响,上述浮式风机动力响应均满足设计指标。[结论]一体化数值计算方法较好地考虑浮式风机耦合动力特性,由于水深限制,近海深水区的海上漂浮式风机对水平运动约束和系泊非线性问题的优化更为重要,响应极值主要发生在极端工况,上述结论为此类漂浮式海上风机基础结构的研究与设计工作提供了一定的参考。

考虑居民热负荷主动需求响应的园区综合能源系统分布式优化运行方法

主动需求侧响应(active demand response,ADR)不仅可降低综合能源系统运行和投资费用,还可应用其灵活性更多地消纳清洁间歇性可再生能源和降低碳排放。为深度挖掘居民热负荷动态特性所蕴含的灵活性ADR资源以及考虑用户隐私需要,该文通过对其进行精细化建模,提出了一种可适用于多用户的园区综合能源系统分布式优化运行方法。首先,对居民热负荷ADR资源进行精细化状态空间建模;其次,以此为基础,建立考虑居民热用户ADR的园区综合能源系统优化运行模型;然后,考虑用户隐私保护需要,提出基于交替方向乘子法将系统整体大规模优化问题解耦为供给侧和需求侧子问题后实现分布式精确求解;最后,通过对含128户居民用户的典型园区综合能源系统算例进行分析,验证了该文方法的有效性。

地下结构整体式反应位移法的改进

整体式反应位移法是目前常用的地下结构抗震实用分析方法,但在求解等效输入地震荷载的过程中,需对自由场土层模型中土-结构交界面所包围的所有土体单元施加自由场惯性力,处理过程相对复杂。该文基于有限元离散模型,从理论上证明了整体式反应位移法中由结构周边应力引起的等效地震荷载可通过仅由一层土体单元构成的子结构模型的一次静力分析获得,由此提出了一种基于土体内部子结构的地下结构整体式反应位移法,即改进方法一;进一步论证了改进方法一中内部土体子结构的惯性力对等效地震荷载的影响可以忽略,在此基础上提出地下结构整体式反应位移法的改进方法二,该方法避免了土层介质自由场惯性力的计算与施加,从而有效简化了整体式反应位移法的实施流程。通过与传统整体式反应位移法的对比分析,验证了该文改进方法具有良好的计算精度,可用于地铁车站、地下隧道等地下结构的地震反应分析与抗震性能研究。

基于随机有限元法的可靠性分析方法概述

基于随机有限元法的可靠性分析方法研究现状,介绍4种常用的随机有限元法:直接蒙特卡洛法、Taylor展开随机有限元法、摄动随机有限元法和Neumann展开随机有限元法,重点介绍了5种基于随机有限元法的可靠性分析方法:应力-强度积分法、功能函数积分法、可靠度指标计算法、随机抽样法和响应面法,并对可靠性研究需要开展的下一步工作进行了探讨。

残矿矿柱回采方案数值模拟与优化研究

为提高柴胡栏子金矿I-4号残矿资源利用率,提出4种残矿矿柱回收方案;基于结构力学模型和ABAQUS有限元软件对4种方案下间柱及顶底柱回收的应力位移时空演化特征进行分析,得到不同矿柱留设方案回采率、位移特征、应力-应变演化规律和塑性应变变化。研究结果表明:随着残矿回采充填,矿柱上应力逐渐向充填体转移,充填区域应力场变为拉应力,间柱上和顶底柱转折处易发生应力集中现象,造成塑形破坏;开采前位移小于0.01 m,开采后顶板垂直位移对开采稳定性的影响比水平位移显著,位移在25~60 cm间变化且最大位移出现在中部区域。利用模糊综合评判法对整体残矿柱回收方案进行优化选择,得到Z型加2个竖条型支撑矿柱回采方案为最佳方案。

基于博弈的多综合能源微网系统优化运行策略

针对考虑综合需求响应和电能交互的冷热电联供多综合能源微网系统,提出一种基于博弈的多综合能源微网优化运行策略。首先,建立各微网运营商与用户之间的双层主从博弈模型,并利用Karush-Kuhn-Tucker(KKT)条件和强对偶定理将双层优化模型转化为单层线性优化模型,以便于快速求解;其次,利用交替方向乘子法(alternating direction method of multipliers,ADMM)对合作联盟中各微网运营商进行分布式优化求解,以保护各微网运营商的信息隐私,针对含电能互济的微网运营商之间利益分配问题,提出基于Shapley值法的合作博弈运行策略;最后,通过算例仿真验证了所提模型和方法的有效性。

大空间隧道结构纵向地震反应分析的整体式反应位移法

大空间地下隧道结构的地震反应特点主要包括两方面:地震波传播方向通常不垂直于结构纵轴,沿纵轴方向结构各点在同一时刻的地震反应并不相同;结构的剪切变形随着横截面尺寸的增大而更加显著。然而,现有的大型地下结构地震反应分析拟静力方法多为针对地震动垂直入射条件下结构横断面地震反应分析的二维方法,难以计算隧道等长线型结构的纵向地震反应;而基于弯曲梁理论提出的纵向整体式反应位移法,虽能完成非一致地震动输入下隧道结构纵向最不利地震反应计算,但无法合理描述结构的剪切变形特点。该文基于大空间隧道结构纵向地震反应的规律和特点,结合铁木辛柯梁理论,确定了通过自由场地震反应获得大空间隧道结构纵向地震反应最不利时刻的方法,发展了适用于大空间隧道结构纵向地震反应分析的整体式反应位移法,并通过数值算例对该方法的有效性和计算精度进行了验证。