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地震动空间变异性对千米级斜拉桥结构随机地震反应的影响 总被引:2,自引:0,他引:2
基于随机振动理论,以苏通长江公路大桥为背景,对超大跨度斜拉桥在随机地震荷载作用下的动力响应展开研究,详细分析地震动空间变化特性对千米级斜拉桥结构动力响应的影响.研究结果表明:相干效应对主梁纵向弯矩影响比较大,尤其是中跨部位;而局部场地效应相对影响较小.对于主梁轴力而言,行波效应影响较为显著,主梁轴力的最大值增大约70%之多,但对竖向剪力并无突出影响.与一致激励比较,行波效应使得跨中竖向位移均方根增大约74%,相干效应为60%,而局部场地效应为13%.对于不同的内力和位移响应,地震动空间变化特性的影响程度和规律不尽相同,必须区别对待,具体问题具体分析. 相似文献
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震源对地震动空间相关性影响的定量研究 总被引:5,自引:2,他引:3
在震尖为线性破裂断层模型的假定下,本文根据震源理论和波谱随空间坐标的展开式,定量分析了震源对地震动空间相关性的影响,得到了场地上相距为d的a、b两点地震动的Fourier谱的关系式为Ab(f)=Aa(f)exp(a1δr0+a2δθ)。其中a1,a2为与震源参数、介质我和场地位置相关并随频率变化的两个复数,δr0与δθ为与台丫相对位置有关的参数。本文给出了计算a1和a2的理论公式,并对a1和a2的 相似文献
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场地条件对地震动参数影响的关键问题 总被引:16,自引:8,他引:8
场地条件对地震动的影响很大,在地震动幅值(如峰值加速度)和频谱特性(如反应谱特征周期)的变化上均有体现,而我国现行抗震设计规范没有考虑不同场地条件下地震动峰值加速度和加速度反应谱平台值的变化。本文介绍了我国现行抗震设计规范中场地类别的划分方法、场地对地震动参数值的规定和存在的问题。详细分析了土层结构、覆盖层厚度等场地条件对地震动峰值加速度和反应谱的影响,以及已经取得的研究成果。最后,就场地分类、影响地震动参数的场地条件、地震动参数随场地条件调整的方法等,提出了有待进一步研究的问题。 相似文献
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随着强震台网的密布及观测记录的增加,为研究各类局部场地地震反应预测模型的合理性提供了有效的参考依据,也使利用强震记录及场地条件研究地震动特征成为可能。选取场地地质参数资料和地震记录数据齐全的日本小田原(Ashigara Valley)盲测试验场地,通过对比不同地震动输入方式及场地反应分析模型,研究地震动特征,分析现有模型的优劣。基于1990年8月5日M5.1强震事件的地表基岩记录和地下基岩地震记录,采用地下台强震记录直接输入、地表基岩台强震记录减半为基底地震动输入、地表基岩台强震记录反演为基底地震动输入作为3种基岩地震动输入。基于局部场地条件分别建立一维等效线性模型、二维黏弹性模型及二维时域等效线性化模型等工程中常用的场地数值分析模型,进行局部场地地震反应分析,预测该盲测场地的地表地震动特征,并与对应的实测强震记录结果进行对比,分析不同基岩地震动输入方式对预测地震动特征及地表土层反应谱特征的影响,重点分析地震动输入、土体非线性、场地横向不均匀性及几何与非线性特征共同作用等因素对地表地震动特征的影响,以期为地表地震动的合理预测提供参考。 相似文献
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南京河西地区设计地震动研究 总被引:7,自引:3,他引:4
本文根据南京及周围地区的地震环境,采用概率法对南京河西地区某高层公寓工程场址进行了地震危险性分析,采用等效线性化模型考虑场地土的非线性特性的影响,并用一维波动模型进行了场址土层地震反应和场地地震动效应分析,给出了50年超越概率63%,10%和3%的场址基岩和地表的水平向加速度反应谱值加速度。 相似文献
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我国时程分析中地震动的选取常用两种方法:规范法和最不利地震动法.为了研究不同方法对超高层结构抗震性能的影响,以某超高层结构为例,采用这两种方法分别选择地震动,用ABAQUS软件对结构进行了罕遇地震下的弹塑性时程分析,将计算得到的结构反应进行了对比分析.结果表明:最不利地震动法中台湾组地震动的结构反应最大,国外组次之,大陆组最小;台湾组和国外组地震动的结构反应比规范法地震动大很多,而大陆组的结果刚好相反. 相似文献
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Simulation of spatially correlated earthquake ground motions for engineering purposes 总被引:4,自引:4,他引:0
A new model to simulate spatially correlated earthquake ground motions is developed. In the model, the main factors that characterize three distinct effects of spatial variability, namely, the incoherency effect, the wave-passage effect and the site-response effect, are taken into account, and corresponding terms/parameters are incorporated into the well known model of uniform ground motions. Some of these terms/parameters can be determined by the root operation, and others can be calculated directly. The proposed model is fi rst verif ied theoretically, and examples of ground motion simulations are provided as a further illustration. It is proven that the ensemble expected value and the ensemble auto-/cross-spectral density functions of the simulated ground motions are identical to the target spectral density functions. The proposed model can also be used to simulate other correlated stochastic processes, such as wave and wind loads. 相似文献
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It is commonly understood that earthquake ground excitations at multiple supports of large dimensional structures are not the same. These ground motion spatial variations may significantly influence the structural responses. Similarly, the interaction between the foundation and the surrounding soil during earthquake shaking also affects the dynamic response of the structure. Most previous studies on ground motion spatial variation effects on structural responses neglected soil–structure interaction (SSI) effect. This paper studies the combined effects of ground motion spatial variation, local site amplification and SSI on bridge responses, and estimates the required separation distances that modular expansion joints must provide to avoid seismic pounding. It is an extension of a previous study (Earthquake Engng Struct. Dyn. 2010; 39 (3):303–323), in which combined ground motion spatial variation and local site amplification effects on bridge responses were investigated. The present paper focuses on the simultaneous effect of SSI and ground motion spatial variation on structural responses. The soil surrounding the pile foundation is modelled by frequency‐dependent springs and dashpots in the horizontal and rotational directions. The peak structural responses are estimated by using the standard random vibration method. The minimum total gap between two adjacent bridge decks or between bridge deck and adjacent abutment to prevent seismic pounding is estimated. Numerical results show that SSI significantly affects the structural responses, and cannot be neglected. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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This paper presents a new way of selecting real input ground motions for seismic design and analysis of structures based on a comprehensive method for estimating the damage potential of ground motions, which takes into consideration of various ground motion parameters and structural seismic damage criteria in terms of strength, deformation, hysteretic energy and dual damage of Park & Ang damage index. The proposed comprehensive method fully involves the effects of the intensity, frequency content and duration of ground motions and the dynamic characteristics of structures. Then, the concept of the most unfavourable real seismic design ground motion is introduced. Based on the concept, the most unfavourable real seismic design ground motions for rock, stiff soil, medium soil and soft soil site conditions are selected in terms of three typical period ranges of structures. The selected real strong motion records are suitable for seismic analysis of important structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake, as they can cause the greatest damage to structures and thereby result in the highest damage potential from an extended real ground motion database for a given site. In addition, this paper also presents the real input design ground motions with medium damage potential, which can be used for the seismic analysis of structures located at the area with low and moderate seismicity. The most unfavourable real seismic design ground motions are verified by analysing the seismic response of structures. It is concluded that the most unfavourable real seismic design ground motion approach can select the real ground motions that can result in the highest damage potential for a given structure and site condition, and the real ground motions can be mainly used for structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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A linear response history analysis method is used to determine the influence of three factors: geometric incoherency, wave-passage,
and local site characteristics on the response of multi-support structures subjected to differential ground motions. A one-span
frame and a reduced model of a 24-span bridge, located in Las Vegas, Nevada are studied, in which the influence of each of
the three factors and their combinations are analyzed. It is revealed that the incoherency of earthquake ground motion can
have a dramatic influence on structural response by modifying the dynamics response to uniform excitation and inducing pseudo-static
response, which does not exist in structures subjected to uniform excitation. The total response when all three sources of
ground motion incoherency are included is generally larger than that of uniform excitation. 相似文献
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研究了地震地面运动多点激励,即空间变化效应对装有铅芯橡胶支座(Lead Rubber Bearing)的连续梁桥地震反应的影响。首先,利用三角级数法生成了拟合规范反应谱的多点人工地震动时程;然后利用非线性时程分析法数值仿真并比较了某五跨LRB隔震连续梁桥在一致激励、仅考虑地震动行波效应、仅考虑地震动部分相干效应、同时考虑行波和部分相干效应以及同时考虑行波、部分相干和局部场地土效应等七种工况下结构的减震效果。行波效应和部分相干效应对铅芯橡胶支座隔震桥梁影响不大,而局部场地土效应对该类桥梁的地震反应分析影响很大,应该引起重视。 相似文献
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近断层脉冲型地震动作用下隔震结构地震反应分析 总被引:17,自引:5,他引:17
隔震结构在远震场地减震效果良好,但是近断层地震动的明显的长周期速度和位移脉冲运动可能对隔震建筑等长周期结构的抗震性能和设计带来不利影响,需要深入探讨。本文首先讨论近断层地震动的长周期脉冲运动特征,然后以台湾集集地震8条典型近震记录和其它4条常用近震记录以及4条远震记录作为地震动输入,对两幢安装铅芯橡胶隔震支座的钢筋混凝土框架隔震结构进行非线性地震反应时程分析,通过比较探讨了算例计算结果,定量说明隔震结构的近震脉冲效应显著,是隔震设计不容忽视的问题。 相似文献
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本研究主要讨论地震动空间变化的随机描述.首先给出了基于密集地震台阵记录估计相干函数的方法,并对计算中需要关注的问题给出了相应的解释;然后对现有的经验和半经验相干函数模型的建立进行了详细的梳理,并对模型在工程应用中的适用性、有效性和局限性进行了讨论;最后通过对比分析不同相干函数模型对场址地震动空间相关性的模拟结果,对相干函数模型的选择提出了建议. 相似文献
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海域地震动是海洋工程建设必须考虑的因素,近年来学者们对海域地震动做了大量研究,这些研究涵盖海域地震动的各方面。为总结对海域地震动特性的研究成果并分析存在的问题,分类阐述了不同学者对海域地震的研究结果。根据采用的研究方法可分为解析方法、数值模拟方法和统计方法。在此基础上,归纳了不同研究方法得出的海域地震动场地影响与传播规律的结论:解析方法与数值方法得出的结论侧重于分析海域地震动受海水、淤泥沉积层与地形等场地条件的影响;统计方法得出的结论集中在海域地震动与陆地地震动在地震动特性与传播规律方面的差异,这些结论可以为采用相同方法的研究提供参考。最后,对当前研究中存在的问题进行探讨,由于数据相对匮乏,导致缺少对海域地震动与陆域地震动差异的定量分析,也缺少对海域地震动不确定性的分析。 相似文献