位移谐波激励下拱顶锚固储罐的动力响应分析

地震中拱顶锚固储罐的破坏将造成严重的后果,研究其地震作用下的动力响应特性具有一定工程意义。以位移简谐波为水平激励,运用AD INA有限元软件对一座3 000m3的拱顶锚固储罐模型进行动力数值模拟,系统分析了储罐内液面晃动波高、动水压力极值、罐壁应力、拱顶应力、拱顶位移等动力响应结果,将以位移谐波激励和以加速度谐波激励的储罐动力响应结果进行比较。分析表明,位移谐波激励下拱顶锚固储罐的液面晃动波高受场地影响较大;储罐应力分布具有一定规律性;采用位移谐波激励时其应力、位移和动水压力等较采用加速度谐波激励时大,液体晃动波高较小。     

地震激励作用下锚固系统研究现状

地震激励作用下,柔性的锚杆支护体系与刚性的滑体合而为一,刚柔并济,协调系统位移与应力,主动抗震抗滑。基于以上优势,锚固边坡在高烈度地区广泛应用,其动力稳定性也成为近年来岩土工程领域研究的热点。通过分析锚固边坡的浅表动力效应、锚固体的动力响应、锚固体的破坏模式、锚固体的抗震机理及设计方法等4个方面发现,浅表动力效应研究和锚固体的动力响应分析研究成果相对较多、较成熟,但大都局限于位移、加速度、应力等单因素的分析,并没有具体到整个系统的动力响应过程;指出今后的研究方向更应趋向于整个锚固系统的动力响应过程、抗震机理及抗震设计理论,才能更好地为工程服务。     

罕遇地震下的屈曲约束支撑框架结构的动力响应研究

为分析支撑布置方式、刚度比、结构总层数等因素在罕遇地震下对屈曲约束支撑框架结构动力响应的影响,借助有限元分析软件SAP2000,分别对6层、12层、18层屈曲约束支撑框架结构模型进行了罕遇地震下的时程分析,详细研究了多高层结构体系的层间位移角、底层剪力、支撑内力等随支撑布置方式、刚度比、结构总层数等因素变化的规律。分析表明,倒V较单斜布置更能有效降低底层剪力、增大支撑轴力、降低层间位移角,从而降低结构的地震响应,更有利于结构消能减震;随着结构总层数的增大,支撑的屈服层数呈现出增多的趋势;刚度比七为2—4时,能使较多层数的屈曲约束支撑参与到消能减震的过程之中,较好地实现抗震设防目标。     

不同小波基下的结构位移反应动力可靠性分析

本文从三种不同小波即：修正的Meyer小波，littlewood-Paley小波，谐波小波的基本概念出发，得出这三种小波基下的地震输入瞬时功率谱，并求出在地震作用下各自的结构位移反应瞬时功率谱，同时定量给出了在这三种小波基下的自由度体系结构位移反应的动力可靠度时程。     

地震作用下储罐与管道连接波纹管的动力响应

针对储罐与管道连接这个抗震薄弱环节进行研究，考虑了储罐与地基、管道与地基的相互弹性作用及流固耦合作用，使计算模型比较符合工程实际情况。将储罐罐壁看作为刚体，将波纹管部分和管道部分分别用旋转锥壳单元和空间梁单元离散化，通过分析得到波纹管与储罐连接接合面、波纹管与管道连接接合面不同单元之间的位移协调约束方程，并用罚函数法进行处理。根据流体力学速度势理论和有限元法的基本理论，利用哈密尔顿变分原理推导出储罐与管道连接波纹管系统动力分析方程，编制了系统动力分析有限元程序，计算了垂直地震激励不同场地土地基条件下储罐与管道连接波纹管位移响应。     

双向地震激励下储罐隔震计算模型对比分析

铅芯橡胶垫基础隔震浮顶储罐在双向地震激励下,采用不同的隔震层恢复力计算模型计算所得的地震响应存在差异.不同工况下,若不加区别地选取将给储罐设计带来不利影响.通过分析高径比、阻尼比、隔震周期以及屈服强度参数对计算结果的影响得出,特定高径比时等效线性模型计算所得波高偏小,基底剪力和位移偏大,因此设计时应综合权衡各模型的计算...     

多高层建筑结构层间位移和层剪力的动力可靠度计算

在虚拟激励法的基础上推导了多高层建筑结构剪切层模型在地震作用下层间相对位移和层地震剪力的自功率谱密度函数的解析表达,通过数值积分获得层间相对位移和层地震剪力的各阶谱矩和标准差,基于随机动力响应过程跨越安全界限次数为泊松过程和两态马尔可夫过程的假设,计算了层间相对位移和层地震剪力的动力可靠度,并用Matlab语言编制了动力可靠度的计算程序.算例表明该方法是高效的和有效的.     

基于位移的模块式加筋土挡墙抗震设计方法研究

性态设计是支挡结构工程抗震设计的前沿科学问题。以模块式加筋土挡墙为试验对象,通过振动台试验,探究模块式加筋土挡墙的变形模式;收集归纳挡土墙位移计算方法,分析不同破坏模式下屈服加速度系数分布规律;对比不同计算方法计算值与实测值的一致性。研究结果表明：挡墙的位移模式为平移与转动耦合,且以转动为主;不同破坏模式下安全系数法求解的屈服加速度系数均随输入加速度幅值增大而减小,简便方法和能量法所得屈服加速度系数为常数;将屈服加速度系数代入不同位移计算方法对比,提出在不同峰值加速度时,可分别采用Richards and Elms上限法(0.4g以下)、Cai and Bathurst平均上限法(0.4g～0.6g)、Newmark上限法(0.6g～0.8g)、Whitman and Liao平均拟合法(0.8g～1.0g)进行位移计算。最后,对模块式加筋土挡墙的抗震设计流程进行归纳。     

运用防屈曲支撑的混凝土框架结构的抗震性能研究

简要介绍地震安全社区的实现途径以及防屈曲支撑的构成和性能参数。运用ABAQUS软件对有无安装防屈曲支撑的钢筋混凝土框架模型进行动力时程分析,总结分析防屈曲支撑对钢筋混凝土框架结构的减震效果。结果表明,防屈曲支撑能大大降低钢筋混凝土框架结构在罕遇地震作用下的层间位移角,提高建筑物抗震性能,使地震安全社区中抗震设防烈度为Ⅶ度的建筑物能够抵御Ⅷ度罕遇地震。     

强震作用下超高桥墩动力稳定性理论研究

根据平截面假定,考虑超高桥墩大位移变形产生的几何非线性影响,建立超高桥墩的振动控制微分方程,利用变步长的龙格-库塔法进行求解,结合B-R运动判定准则,对超高桥墩在地震作用下的动力失稳机理进行研究。理论分析表明,超高桥墩的动力失稳与桥墩的几何尺寸、质量分布、边界条件有密切关系;桥墩动力失稳时刻随地震波加速度峰值的增大而减小;失稳时刻与失稳加速度荷载有对应关系。算例结果表明:本文方法正确,利用本文理论能够准确计算超高桥墩的失稳时刻及失稳加速度,对超高桥墩动力失稳的理论分析及工程实践有重要指导意义。     

Investigation of sloshing damping in baffled rectangular tanks subjected to the dynamic excitation

In this research, an analytical model is developed to estimate the hydrodynamic damping ratio of liquid sloshing for wall bounded baffles using the velocity potential formulation and linear wave theory. Here, an analytical solution approach and experimental investigations are conducted for describing the hydrodynamic damping which is provided by vertical and horizontal baffles in partially filled rectangular liquid tanks. In order to evaluate the accuracy of the analytical solution which is developed in present work, a series of experiments are carried out with a rectangular liquid tank excited by harmonic oscillation. The parametric study is conducted on the damping efficiencies of both vertical and horizontal baffles with various dimensions and locations. According to the results of the present investigations, the hydrodynamic damping is significantly affected by the size and location of baffles. Furthermore, the validity of the developed analytical approach as well as the effectiveness of various baffle configurations are discussed. Finally, a simple approach is proposed for estimating the damping ratios of the baffles during earthquake motions.     

Sloshing behaviours of rectangular and cylindrical liquid tanks subjected to harmonic and seismic excitations

A numerical and experimental study on the sloshing behaviours of cylindrical and rectangular liquid tanks is addressed. A three‐dimensional boundary element method for space with the second‐order Taylor series expansion in time is established to simulate the sloshing phenomenon and its related physical quantities inside a liquid tank subjected to horizontal harmonic oscillations or recorded earthquake excitations. The small‐scale model experiments are carried out to verify some results of numerical methods in this study. The comparisons between numerical and experimental results show that the numerical method is reliable for both kinds of ground excitations. Finally, the water wave and the base shear force of a rectangular tank due to harmonic excitation are also presented at different frequencies. A huge cylindrical water tank subjected to a recorded earthquake excitation is used for application and discussion. Copyright © 2007 John Wiley & Sons, Ltd.     

Periodic response of a rigid block resting on a footing subjected to harmonic excitation

This study presents the dynamic behaviour of a rigid block which rests on a footing supported by a spring and a dashpot on a rigid base. The response of the rigid body is examined carefully when the base is excited by a harmonic force. It is found that a periodic motion appears in three different modes: stick-stick, stick-slip and slip-slip. The conditions that initiate the stick-stick and slip-slip modes are derived in explicit forms and the maximum sliding displacement is also obtained analytically. Useful dimensionless parameters are proposed for the presentation of the dynamic behaviour. The accuracy of results is confirmed by the response history computed by the Nigam-Jennings method.     

Method for solving dynamic equilibrium equations based on displacement excitation

Mode superposition is a widely used method for solving the dynamic equilibrium equation in structural dynamic analysis. However, the accuracy of this method may be reduced when the dynamic equilibrium equations are set up using displacement excitation. A new method for developing solutions for dynamic equilibrium equations based on displacement excitation is introduced. The dynamic equilibrium equation is decomposed into two parts, namely displacement excitation and velocity excitation, and precise integration and mode superposition methods are combined to solve the equation. Ritz vectors are then used to calculate the static response of the truncated modes of the structure, and a method for determining the number of participating modes is obtained. Using multi-degree-of-freedom systems as two computational examples, the differences in the structural responses obtained from the displacement excitation and acceleration excitation are compared and analyzed. It is shown that the new solution method generates consistent accuracy between the displacement excitation and acceleration excitation.     

简谐荷载下单层球面网壳动力失效机理研究

以具有实际工程意义的40m跨度K8型单层球面网壳为研究对象,采用ANSYS程序的Pipe20单元,考察不同矢跨比网壳在不同频率的简谐荷载作用下,随着荷载幅值的逐渐增大,其宏观和微观响应的变化,详细阐述了2类破坏行为的规律,并通过一定规模的参数分析,给出单层球面网壳动力强度破坏判别准则.     

Model for multiblock columns subjected to base excitation

A new model is presented for multiblock columns subjected to earthquakes, which contains an impact and an opening model. Both in the impact and in the opening model, all the possible opening configurations are investigated because it was found that in many practical cases, unexpected patterns may occur. The model is purely mechanical: assuming rigid blocks and classical (inelastic) impact. The effect of energy dissipation during impact was investigated. Using our model in accordance with the literature, it was found that monolithic blocks are more vulnerable to overturning than multiblock systems.     

Elastically supported cantilever beam subjected to nonstationary seismic excitation

The dynamic behaviour of bridge piers under seismic load is studied here in the context of random vibration. The earthquake excitation is modelled as white noise filtered by the Clough–Penzien filter in cascade with modulation accounting for intensity non-stationarity. The bridge pier modelled as an elastically supported cantilever beam witha lumped mass at the top. An analytical solution is presented for the response statistics, which may be used to develop probabilistic seismic response spectra for design. It is found that the first two modes of the pier approach to rigid-body motion when the stiffness of the elastic support decreases. Seismic responses increase with the top mass, resultingin significantly high displacement and shear but negligible moment at the top, and higher shear and moment at thebase. Lower stiffness of the elastic support increases the pier top displacement and moment responses, but may increase or reduce shear responses. The probabilistic spectrum of the relative displacement between the bridge superstructure and the pier top may depend on the two systems’ relative modal properties. © 1998 John Wiley & Sons, Ltd.     

Periodic response of a sliding oscillator system to harmonic excitation

This paper deals with the periodic response of an oscillating system which is supported on a frictional interface. The base excitation is assumed harmonic and the frictional force is assumed to be of the Coulomb type. Though each segment of the motion of such a system is described by linear equations, its complete response is highly non-linear and varied. The most fundamental periodic solutions are derived analytically and numerically. The results indicate that such a system has several subharmonic resonant frequencies and that while the friction reduces the peak response of the system when it is excited at its ‘fixed-base’ natural frequency, ω_n, the sliding can induce considerably higher levels of response, when compared with those of a non-sliding, fixed-base system, for frequencies less than ω_n. The results obtained herein may find application in the area of vibration isolation.