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本文基于带集中参数边界条件的分布参数连续梁理论,推导规则隔震梁桥单墩-质点(SCM)地震时程响应的计算步骤.在控制方程边界条件引入等效基础弹簧和墩顶隔震层变形协调条件,解析地获得各阶实模态,用牛顿法搜索各阶频率.为了处理隔震层非比例阻尼产生的耦联效应,由能量法分配各阶实振型的隔震层附加阻尼比,实现体系的实模态近似解耦,应用振型叠加法求解体系的地震时程响应.最后应用该方法对一规则隔震梁桥SCM体系的地震响应进行分析,与有限元时程积分的结果进行比较,表明此方法的有效性.计算结果表明,采用墩顶隔震策略的单墩-质点体系能显著减小结构响应,具有良好的减震效果. 相似文献
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阻尼器参数的确定是利用阻尼器连接相邻结构进行减震设计的关键.根据随机地震反应理论,以相邻结构的频率比和质量比为参数,推导了结构位移反应均方差与连接阻尼比的关系式,得到了相邻结构的地震反应与频率比、质量比以及连接阻尼比的影响规律,从而得到了连接阻尼器的优化设计参数.根据自振频率相等的原则,探讨了将多自由度体系简化为单自由度体系的分析方法.最后在El Centro波、Taft 波及人工波激励下,对比分析了某相邻10层建筑结构有连接和无连接时的地震反应,表明黏滞阻尼器连接相邻结构具有较好的减震效果.本分析方法可供相邻结构减震设计参考. 相似文献
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钢结构与混凝土结构阻尼比不同,混凝土房屋与其顶上钢塔组成了非比例阻尼结构系统。本文用非经典振型分解法求解该类结构系统的线弹性地震响应,发现只用前几阶振型响应迭加的结果即可逼近直接积分法的精确度。 相似文献
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为研究打桩荷载作用下自由场土体振动衰减规律，建立了考虑桩-土相互作用的二维有限元数值模型，并通过Lamb问题解析解验证了数值模型的有效性。通过分析打桩深度、土体阻尼比、打桩荷载等级和土质条件等因素的影响，研究了土体表面振动特性及振动衰减规律。参数分析表明，打桩深度对微振动的影响较小，在距振源一定距离处的土体表面振动响应基本保持一致；土体阻尼比对土体表面振动的影响显著，阻尼比越小，土体表面振动响应越剧烈；不同场地软硬条件影响微振动的限制距离，在一定距离范围内，土质越软，土体表面振动响应越显著，防振距离越长。基于参数分析结果，对峰值速度衰减曲线进行拟合，拟合公式计算结果与模拟结果较吻合，可为振动敏感建筑场地的选择提供参考。 相似文献
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《地震工程与工程振动》2015,(3)
基于多子台台阵系统,北京工业大学于近期开展了多点地震动输入、不同场地条件下埋地管道振动台试验。试验中连续体模型箱固定于3个振动台台面上,相邻台面上的箱体能在水平双方向(纵向、横向)相对运动;3个振动台相互独立,通过分别对3个振动台输入各自的加速度记录实现了多点地震动输入。本文针对其中的横向水平地震激励作用下的场地响应进行研究,分析了一致和非一致地震作用下有无埋地管线时的场地地震响应规律。试验结果表明,非一致激励作用将增大场地土体的相对位移,致使相邻地震动输入点间场地土体受到剪切作用;随着输入地震动强度的增加,场地土体的一阶固有频率持续降低,阻尼比不断增大;非自由场的阻尼比、一阶固有频率等参数略大于自由场。 相似文献
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对一维剪切条计算模型进行改进,提出了土石坝非线性地震反应的简化计算方法。首先将坝体沿坝高离散为一系列的具有不同剪切刚度与阻尼比等参数特性的层状体系,建立了各层的振动控制方程及其边值条件,进而采用数学物理方程方法进行了求解,确定了体系的振动特性,并根据振型叠加原理和Duhamel积分确定了坝体地震反应的线弹性解。采用等价线性化方法考虑坝料的动力非线性性质,通过对线弹性地震响应的反复迭代计算,使得各层土的模量和阻尼比与其相应的剪应变水平相协调,确定出与非线性坝体系统相等效的线性解答,并将所得到的地震响应作为非线性地震响应的近似解。最后,以均质坝和心墙坝作为算例进行了具体的数值计算,将所得结果与有限元数值解进行对比分析,论证了所提方法的适用性和合理性。 相似文献
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Coupling adjacent buildings using discrete viscoelastic dampers for control of response to low and moderate seismic events is investigated in this paper. The complex modal superposition method is first used to determine dynamic characteristics, mainly modal damping ratio and modal frequency, of damper-linked linear adjacent buildings for practical use. Random seismic response of linear adjacent buildings linked by dampers is then determined by a combination of the complex modal superposition method and the pseudo-excitation method. This combined method can effectively and accurately determine random seismic response of non-classically damped systems in the frequency domain. Parametric studies are finally performed to identify optimal parameters of viscoelastic dampers for achieving the maximum modal damping ratio or the maximum response reduction of adjacent buildings. It is demonstrated that using discrete viscoelastic dampers of proper parameters to link adjacent buildings can reduce random seismic responses significantly. Copyright © 1999 John Wiley & Sons Ltd. 相似文献
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Closed‐form solution for seismic response of adjacent buildings connected by hydraulic actuators with linear quadratic Gaussian (LQG) controllers is presented in this paper. The equations of motion of actively controlled adjacent buildings against earthquake are first established. The complex modal superposition method is then used to determine dynamic characteristics, including modal damping ratio, of actively controlled adjacent buildings. The closed‐form solution for seismic response of the system is finally derived in terms of the complex dynamic characteristics, the pseudo‐excitation method and the residue theorem. By using the closed‐form solution, extensive parametric studies can be carried out for the system of many degrees of freedom. The beneficial parameters of LQG controllers for achieving the maximum response reduction of both buildings using reasonable control forces can be identified. The effectiveness of LQG controllers for this particular application is evaluated in this study. The results show that for the adjacent buildings of different dynamic properties, if the parameters of LQG controllers are selected appropriately, the modal damping ratios of the system can be significantly increased and the seismic responses of both buildings can be considerably reduced. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Dynamic characteristic and harmonic response of adjacent buildings connected by fluid damper were experimentally investigated using model buildings and fluid damper. Two building models were constructed as two three-storey shear buildings of different natural frequencies. Model fluid damper connecting the two buildings was designed as linear viscous damper of which damping coefficient could be adjusted. The two buildings without fluid dampers connected were first tested to obtain their individual dynamic characteristics and responses to harmonic excitation. The tests were then carried out to determine modal damping ratios of the adjacent buildings connected by the fluid damper of different damping coefficients and at different locations. Optimal damper damping coefficient and location for achieving the maximum modal damping ratio were thus found. The measured modal damping ratios and harmonic responses of the building-fluid damper system were finally compared with those from the individual buildings. The comparison showed that the fluid damper of proper parameter could significantly increase the modal damping ratio and tremendously reduce the dynamic response of both buildings. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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本文基于虚拟激励法和留数定理推导出毗邻建筑考虑局部场地效应时在平稳随机地震激励下的LQG控制问题的闭合解。利用此闭合解进行场地土参数研究表明,场地土参数对位移和加速度响应的影响是不同的,甚至是相反的。因此对于给定的LQG控制加权阵Q和R,场地土的卓越频率和阻尼比变化对减震效果有显著影响,应予以重视。 相似文献
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Rakesh K. Goel 《地震工程与结构动力学》2000,29(4):461-480
This paper investigates the response of asymmetric‐plan buildings with supplemental viscous damping to harmonic ground motion using modal analysis techniques. It is shown that most modal parameters, except dynamic amplification factors (DAFs), are affected very little by the plan‐wise distribution of supplemental damping in the practical range of system parameters. Plan‐wise distribution of supplemental damping significantly influences the DAFs, which, in turn, influence the modal deformations. These trends are directly related to the apparent modal damping ratios; the first modal damping ratio increases while the second decreases as CSD moves from right to left of the system plan, and their values increase with larger plan‐wise spread of the supplemental damping. The largest reduction in the flexible edge deformation occurs when damping in the first mode is maximized by distributing the supplemental damping such that the damping eccentricity takes on the largest value with algebraic sign opposite to the structural eccentricity. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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Rakesh K. Goel 《地震工程与结构动力学》2001,30(9):1399-1416
This study investigated the effects of neglecting off‐diagonal terms of the transformed damping matrix on the seismic response of non‐proportionally damped asymmetric‐plan systems with the specific aim of identifying the range of system parameters for which this simplification can be used without introducing significant errors in the response. For this purpose, a procedure is presented in which modal damping ratios computed by neglecting off‐diagonal terms of the transformed damping matrix are used in the traditional modal analysis. The effects of the simplification are evaluated first by comparing the aforementioned modal damping ratios with the apparent damping ratios obtained from the complex‐valued eigenanalysis. The variation of a parameter that was defined by Warburton and Soni as an indicator of the errors introduced by the simplification is examined next. Finally, edge deformations obtained from the simplified procedure are compared with those obtained from the direct integration of the equations of motion. It is found that the simplified procedure may be used without introducing significant errors in response for most practical values of the system parameters. Furthermore, estimates of the edge deformations, in general, tend to be on the conservative side. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Four real buildings with three to six stories, strong irregularities in plan and little engineered earthquake resistance are subjected to inelastic response‐history analyses under 56 bidirectional EC8‐spectra‐compatible motions. The average chord rotation demand at each member end over the 56 response‐history analyses is compared to the chord rotation from elastic static analysis with inverted triangular lateral forces or modal response spectrum analysis. The storey‐average inelastic‐to‐elastic‐chord‐rotation‐ratio was found fairly constant in all stories, except when static elastic analysis is applied to buildings with large higher mode effects. Except for such buildings, static elastic analysis gives more uniform ratios of inelastic chord rotations to elastic ones within and among stories than modal response spectrum analysis, but generally lower than 1.0. With increasing EPA the building‐average inelastic‐to‐elastic‐chord‐rotation‐ratio decreases but scatter in the results increases. Static elastic analysis tends to overestimate the inelastic torsional effects at the flexible or central part of the torsionally flexible buildings and underestimate them at their stiff side. Modal response spectrum analysis tends to overestimate the inelastic torsional effects at the stiff or central part of the torsionally stiff buildings and underestimate them at the flexible side. Overall, for multistorey RC buildings that typically have fundamental periods in the velocity‐sensitive part of the spectrum, elastic modal response spectrum analysis with 5% damping gives on average unbiased and fairly accurate estimates of member inelastic chord rotations. If higher modes are not significant, elastic static analysis in general overestimates inelastic chord rotations of such buildings, even when torsional effects are present. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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This study investigates the effectiveness of the modal analysis using two‐degree‐of‐freedom (2DOF) modal stick to deal with the seismic analysis of one‐way asymmetric elastic systems with supplemental damping. The 2DOF modal stick possessing the non‐proportional damping property enables the modal translation and rotation to not be proportional even at elastic state. The analytical results of one‐storey and three‐storey buildings obtained by the proposed method are compared with those obtained by direct integration of the equation of motion and conventional approximate method, which neglects the off‐diagonal elements in the transformed damping matrix. It is found that the proposed simplified method, compared to conventional approximate methods, can significantly improve the accuracy of the analytical results and, at the same time, without obviously increasing computational efforts. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Supplemental damping could mitigate the earthquake‐induced damage in buildings with asymmetric plan, known to be more vulnerable to damage than comparable symmetric‐plan buildings. This investigation aims to improve the understanding of how and why planwise distribution of fluid viscous dampers (FVDs) influences the response of linearly elastic, one‐storey, asymmetric‐plan systems. Starting with vibration mode shapes, we predict this influence on the modal damping ratios, and in turn on the individual modal responses and the total response. These predictions are confirmed by the computed responses, which demonstrated that the reduction in earthquake response of the system achieved by supplemental damping is strongly influenced by its planwise distribution, which is characterized by four parameters. Identified are asymmetric distributions of supplemental damping that are more effective in reducing the response compared to symmetric distribution. The percentage reduction achieved by a judiciously selected asymmetric distribution can be twice or even larger compared to symmetric distribution. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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The optimum parameters of tuned mass dampers (TMD) that result in considerable reduction in the response of structures to seismic loading are presented. The criterion used to obtain the optimum parameters is to select, for a given mass ratio, the frequency (tuning) and damping ratios that would result in equal and large modal damping in the first two modes of vibration. The parameters are used to compute the response of several single and multi-degree-of-freedom structures with TMDs to different earthquake excitations. The results indicate that the use of the proposed parameters reduces the displacement and acceleration responses significantly. The method can also be used in vibration control of tall buildings using the so-called ‘mega-substructure configuration’, where substructures serve as vibration absorbers for the main structure. It is shown that by selecting the optimum TMD parameters as proposed in this paper, significant reduction in the response of tall buildings can be achieved. © 1997 John Wiley & Sons, Ltd. 相似文献