摩擦摆基础隔震上部偏心结构地震反应影响因素分析

对上部结构存在偏心的摩擦摆基础隔震结构进行了水平双向地震作用下的地震反应分析,研究了上部结构偏心距和抗扭刚度对结构地震反应的影响。分析表明:上部结构偏心距对上部结构和隔震层的位移反应和加速度反应均有较大影响,即使在上部结构偏心距较小时,其对结构地震反应仍有一定程度的影响;上部结构的抗扭刚度对上部结构的加速度反应影响较小,而对上部结构的位移反应影响较大;上部结构的抗扭刚度对隔震层的加速度反应和位移反应影响较小。因而,对于上部结构存在偏心的摩擦摆基础隔震结构,应减小上部结构偏心距并增大其抗扭刚度以减小摩擦摆基础隔震结构的扭转反应。     

基础隔震单层偏心结构扭转地震反应分析

采用微分型滞回恢复力模型模拟隔震支座的恢复力特性，对基础隔震单层偏心结构的扭转地震反应进行分析，研究隔震系统偏心距和上部结构偏心距对结构扭转反应的影响。结果表明，采用隔震技术可以显著降低隔震结构的扭转地震反应。     

偏心多塔结构同基础隔震效果分析

偏心隔震结构在地震动作用下,除发生平动外,还将发生平-扭耦联的反应,从而使震害加重,尤其是隔震层较易发生破坏。本文利用自行编制的分析程序,对偏心多塔隔震结构进行了数值分析,在此基础上,提出偏心多塔结构同基础隔震的设计方案。数值模拟计算结果表明,对偏心单塔隔震结构,在地震作用下采用多塔同基础隔震的方案,能大幅度降低结构隔震层的扭转反应,其中最大扭转加速度最少降低55%,最大扭转角最少降低84%。可见,在条件许可时,将相邻偏心单塔结构采用同基础隔震的方案,对提高隔震效果是有利的。     

上部结构与基础隔震层偏心对结构地震响应的影响

随着基础隔震技术的发展,我国在高烈度地区广泛开展基础隔震技术的工程应用必将成为一种趋势,但由于建筑功能和建筑造型的丰富多彩,结构的质量中心和刚度中心也趋于分布不均匀,以三层的钢框架结构为分析模型,利用结构分析软件Sap2000对上部结构质量中心和隔震层质量中心、刚度中心分布不均匀的三种方案进行单向水平地震作用下的非线性时程分析,分析结果表明:上部结构质量中心与隔震层质量中心存在偏心距对结构的扭转效应以及地震响应有较大的影响,减小上部结构的偏心距对调整结构的水平地震响应的影响成效最为显著;对于隔震层而言,隔震层的刚度中心偏心距较质量中心偏心距对上部结构的影响更大,有效控制隔震层刚度中心的偏心距在隔震设计中会更加有效。     

层间隔震偏心结构双向地震耦合响应研究

建立双向地震作用下层间隔震双向偏心结构侧扭耦联分析模型;考虑上部结构及下部结构的弹塑性模型,隔震支座采用双向耦合非线性Bouc-wen模型模拟;分析偏心参数对层间隔震双向偏心结构的影响规律;评价双向地震作用下我国抗震规范给出的扭转影响系数静力预测值的准确性。结果表明,双向地震作用下设置中间柔性隔震层可以减小上\,下部结构扭转的耦连效应;下部结构存在双向偏心会对隔震层和下部结构扭转反应带来不利影响;LRB耦合效应对层间隔震地震响应影响较小;当下部结构偏心率较大时现行规范计算扭转系数偏于不安全。     

基于强震观测的隔震结构地震反应分析

福建省防灾减灾中心大楼是一栋高约40m,安装有强震观测系统的隔震大楼,目前该结构台阵已记录到30多次地震引起的大楼地震反应。本文利用具有强大非线性功能的ETABS软件建立大楼结构模型,同时考虑隔震结构的楼梯和填充墙对结构地震反应的影响,并利用台阵记录验证大楼结构模型线弹性地震反应的可靠性,说明隔震大楼结构模型能很好地模拟大楼的地震反应过程。在此基础上结合大楼原型动力性能实验的实测参数,以大楼自由场地的三个实际地震记录作为输人,对大楼在中小地震作用下非线性地震反应进行分析,结果表明大楼具有良好的隔震效果。     

单层FPS隔震结构的平移-扭转耦合性能分析

本文推导了FPS(Friction Pendu lum System)隔震结构在平移-扭转耦联情况下的动力反应方程,计算了单层框架结构的地震响应。分析了上部结构偏心对地震反应的影响,对比了结构在不同偏心时的反应并分析了FPS隔震装置的摩擦系数、滑道半径对其抗震性能的影响。     

小高宽比隔震结构双向输入振动台试验研究及数值分析

本文对高宽比为2.5的普通钢框架隔震结构模型,采用多种不同的地震动进行了水平向和竖向双向地震输入的振动台试验研究,并利用时程分析法完成了模型结构地震反应的数值分析。试验结果表明,高宽比隔震结构在水平向和竖向双向输入情况下隔震层基本上不会进入拉伸应力状态,即使在9度大震E l Centro和Hach inohe波输入时,隔震层支座仍以受压为主。因此小高宽比隔震结构在场地好的情况下,结构不会出现倾覆,仅需考虑软弱土场地的受拉情况。试验发现竖向地震输入对小高宽比隔震结构水平反应的影响相当小;对小高宽比隔震结构进行水平向地震反应分析时,可以忽略竖向地震对结构的影响。     

刚性结构基础隔震随机地震响应及优化分析

运用随机振动的时域复模态分析方法，对刚性结构房屋基础隔震体系在平稳随机地震激励下的响应进行了分析，得出隔震结构体系的地震反应统计特征。在此基础上，结合基础隔震结构均方响应和地震激励均方值之比与频率比、阻尼比的关系曲线以及基于失效概率下位移限值与频率比、阻尼比的关系曲线，提出采用图解法确定隔震装置合理优化的参数取值。     

单轴平扭耦联基础隔震结构动力简化分析

为了建立单轴平扭耦联基础隔震结构的动力简化分析方法,探讨了影响结构扭转反应的参数取值规律,首先基于层单元模型,通过假定上部结构楼层回转半径、偏心距、弹力半径相等,推导了单轴平扭耦联基础隔震结构线性化的动力计算方程;其次,运用该简化分析方程,通过一算例进行了动力响应的参数分析。结果表明:调整隔震层刚心使其与上部结构质心位置接近,可显著降低偏心隔震结构扭转反应;增大隔震层刚度半径及阻尼半径可有效减少或抑制结构扭转反应;所建简化分析方程能有效模拟偏心隔震结构动力响应。     

正弦行波激励下单层偏心框架结构扭转响应的解析解

文中针对单层偏心框架结构,利用正弦行波激励研究了质量偏心率和激励频率对偏心框架结构行波扭转响应的影响规律.建立了行波激励下单层偏心框架结构的振动方程,采用相对运动法求解给出了正弦行波激励下单层偏心框架结构楼板的质心平动位移和转角位移以及楼板扭矩和柱剪力的解析解.计算了一个钢筋混凝凝土单层偏心框架结构的峰值楼板扭矩和峰值...     

基于不同参数的基础隔震结构非线性概率密度演化

为了研究不同设计参数条件下基础隔震结构非线性响应的概率密度演化特征,采用两质点模型来模拟基础隔震结构,隔震层与上部结构分别采用Bouc-Wen模型与刚度退化的Bouc-Wen模型来描述其非线性特征,运用概率密度演化理论,进行隔震结构非线性随机地震响应的概率密度演化分析。采用基于物理的随机地震动模型生成人工地震动,提出基础隔震结构非线性随机地震响应的概率密度演化分析的基本步骤。通过改变基础隔震结构的设计参数,同时考虑激励的随机性,研究基础隔震结构非线性随机地震响应的概率密度演化规律。结果表明,基础隔震结构的阻尼比、周期比和屈重比取合理范围,能使隔震结构上部和下部的位移可控。     

Effective eccentricity for inelastic seismic response of buildings

The concept of effective eccentricity is generalized for inelastic systems to provide guidelines for estimating the maximum dynamic edge displacement and resisting element deformation of a single mass monosymmetrical system subjected to unidirectional ground excitations. Inelastic responses of three structural models having the same overall elastic responses are compared and the model which generally results in larger edge displacement is chosen as the structural model to be used to evaluate the effect of asymmetry. The inelastic effective eccentricity is calculated for different values of the system parameters, based on an ensemble of six ground motion records as input. It is concluded that, except for stiff structures having low yield strength, the elastic effective eccentricity curves developed previously by Dempsey and Tso can provide a reasonable or relatively conservative estimate for inelastic effective eccentricity, and these curves can be used to estimate the edge displacement and element deformation of inelastic eccentric systems.     

近场地震动下偏心结构的减震控制研究

本文选用远场宽频地震Kanai-Tajimi模型与近场地震He-Agrawal速度脉冲模型,对现有的典型近场地震记录进行了非线性数值拟合。通过调整脉冲分量与宽频分量的比值,得到了不同脉冲分量的地震波,分析了在合成近场地震波作用下,设置粘滞阻尼器时偏心结构的动力反应,并与未设置阻尼器时结构的地震响应进行了对比,同时也对能反映结构偏心特性的参数进行了分析研究。通过数值模拟与仿真分析,得到了一些对实际工程设计有意义的结论。     

An alternative approach for computing seismic response with accidental eccentricity

Accidental eccentricity is a non-standard assumption for seismic design of tall buildings. Taking it into consideration requires reanalysis of seismic resistance, which requires either time consuming computation of natural vibration of eccentric structures or finding a static displacement solution by applying an approximated equivalent torsional moment for each eccentric case. This study proposes an alternative modal response spectrum analysis(MRSA) approach to calculate seismic responses with accidental eccentricity. The proposed approach, called the Rayleigh Ritz Projection-MRSA(RRP-MRSA), is developed based on MRSA and two strategies:(a) a RRP method to obtain a fast calculation of approximate modes of eccentric structures; and(b) an approach to assemble mass matrices of eccentric structures. The efficiency of RRP-MRSA is tested via engineering examples and compared with the standard MRSA(ST-MRSA) and one approximate method, i.e., the equivalent torsional moment hybrid MRSA(ETM-MRSA). Numerical results show that RRP-MRSA not only achieves almost the same precision as ST-MRSA, and is much better than ETM-MRSA, but is also more economical. Thus, RRP-MRSA can be in place of current accidental eccentricity computations in seismic design.     

Seismic response of the superstructure and attached equipment in a base-isolated building

Base isolation can be used both to protect the structure and simultaneously to reduce the response of internal equipment. The seismic response of a base-isolated structure has been studied through the shaking table test or numerical calculation before. The object of this paper is to analyse a base-isolated structure by a different analytical approach—perturbation analysis. Recognizing that the horizontal stiffness of an isolation system is much smaller than that of the superstructure, the mathematical expressions of the modal properties of base-isolated structures are derived by the perturbation method in terms of the modal properties of the superstructure and used to study the dynamic response of superstructure and attached equipment in the base-isolated building. This study shows that the first base-isolated mode not only controls the superstructural response but also dominates the response of high-frequency attachment. The contribution of higher modes to the response of base-isolated structures, which is proportional to the horizontal stiffness of isolation system, is very small.     

Inelastic earthquake response of single‐story asymmetric buildings: an assessment of simplified shear‐beam models

The inelastic seismic torsional response of simple structures is examined by means of shear‐beam type models as well as with plastic hinge idealization of one‐story buildings. Using mean values of ductility factors, obtained for groups of ten earthquake motions, as the basic index of post‐elastic response, the following topics are examined with the shear‐beam type model: mass eccentric versus stiffness eccentric systems, effects of different types of motions and effects of double eccentricities. Subsequently, comparisons are made with results obtained using a more realistic, plastic hinge type model of single‐story reinforced concrete frame buildings designed according to a modern Code. The consequences of designing for different levels of accidental eccentricity are also examined for the aforementioned frame buildings. Copyright © 2003 John Wiley & Sons, Ltd.     

UNCOUPLED FREQUENCY RATIO IN ASYMMETRIC BUILDINGS

Structural eccentricity and Uncoupled Frequency Ratio (UFR) are two system parameters that strongly influence the elastic response of eccentric structures. The opinions differ regarding their influence on the inelastic response. Different investigators arrived at contradictory conclusions on the influence of uncoupled frequency ratio. The reasons for these contradictions are the use of different definitions and different models in the inelastic studies. In this paper, three possible definitions of the uncoupled frequency ratio are identified, and their influence is studied on the inelastic response. An ensemble of 10 real earthquakes of 20 s duration is used. The response is measured in terms of the mean plus one standard deviation of the ductility ratio. The value of the UFR obtained by each of the three possible definitions is not always admissible. It is concluded that the inelastic response depends upon the eccentric system, definition employed for the UFR, time period of the eccentric systems and the basis of strength distribution among the various lateral elements.     

建筑物偏心结构对其抗震性能的影响

偏心对建筑物的抗震效果有很大的影响。在对三种常见建筑物框架结构在偏心扭矩作用下的受震反应进行数值模拟时,采用6层建筑物模型,通过三维非线性模拟偏心结构对建筑物抗震性能影响的分析,采用最大层间位移作为衡量标准,绘制易损曲线来进行结果分析。结果显示:若忽略意外扭矩的影响,可能会高估钢结构体系的抗震性能,而影响安全评估结果;如果采用全层5%质量偏心来考虑意外偏心扭矩的话,会低估钢结构建筑物的抗震性能。     

基础隔震结构抗震可靠度简化分析方法

选用胡聿贤平稳地震地面运动模型作为基础隔震结构的随机地震动输入,采用Bouc-Wen模型描述隔震结构的层间滞变位移,将滞变体系动力特性矩阵随机等效线性化,并建立等价线性状态方程。引入左右特征向量系,对振动微分方程进行解耦,推导了基础隔震结构随机地震响应的统计矩解析解。采用变形失效准则,定义了上部结构和隔震层的功能状态极限函数。在此基础上,采用首次超越破坏模型,基于Possion分布假设和串联系统可靠度模型,建立了从整体上评价基础隔震体系抗震可靠度的简化分析方法。最后,通过一个基础隔震框架结构计算实例,说明了这种方法的运用。