共查询到17条相似文献，搜索用时 140 毫秒
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渤海海域软土层土对场地设计地震动参数取值具有显著影响。选取渤海中部钻孔剖面作为计算场地模型基础,分别构建软土和硬土场地模型,并通过改变软土层厚度,构造新的场地模型。采用等效线性化方法（EL法）和非线性计算方法（NL法）分别对场地模型进行地震反应分析,分析了海底软土层土对地震动参数的影响。研究结果表明:海底软土层土对地震动峰值加速度的影响显著,随着地震动输入增加,软土层放大效应减弱,减震作用逐渐增强;EL法中,软土层土对基岩反应谱的高频部分具有明显滤波作用,而NL法中,滤波作用较弱,海底面反应谱随地震动输入的增大先放大后减小;软土层土会降低设计地震动地震最大影响系数,增大特征周期。对于海域工程,特别是深基础工程抗震设计地震动参数的确定,从保守角度考虑,建立场地模型时建议删除软土层。 相似文献
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根据特定震源机制、震级、断层距和场地条件选取69条地震动记录并进行分组,利用Nspectra软件计算隔震结构的弹塑性位移反应谱,分析断层距、场地条件、震级、阻尼比对弹塑性位移谱的影响,探讨隔震层的力学参数对地震能量耗散的影响。研究结果表明:相较于远场,处于近场的隔震结构最为不利,隔震层位移谱值受场地条件、地震加速度和速度大小影响较大;随着断层距的增大,位移谱值衰减较快,且在软土场地中隔震层的位移谱值衰减幅度大于硬土场地;地震震级大小对位移谱形状的影响不明显,但能够使隔震层的位移谱值产生整体缩放效应;阻尼比在小于0.4的范围内,隔震层在不同地震动特性作用下位移谱值差别较大,但在大于0.4以后,位移谱值及谱形基本趋于一致;屈服力较小(恢复力/重力小于等于1)的隔震层随自振周期增大其耗能性能更加突出。 相似文献
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烟台海岸软土场地特征及对地震动参数的影响 总被引：1，自引：0，他引：1
本文利用剪切波速和钻孔资料，根据中国GB50011-2001规范、美国FEMA-NEHRP规范、欧洲EUROCODE 8规范，对烟台滨海软土场地类别进行评定。并通过场地地震动效应分析，研究滨海场地土特征对地震动的影响。结果表明，简单的场地类别划分难以反映软土场地的实际情况；滨海软土场地对地震动加速度的幅值和频谱的影响非常明显，其对峰值加速度的放大倍数较高，但受土的非线性变形影响，随地震动输入的增大其放大倍数呈非线性降低；软土场地使得加速度反应谱谱形变宽，特征周期变大。 相似文献
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选取日本熊本MW7.0地震断层距小于200 km的82个近场KiK-net台站记录到的三分量记录数据进行基线校正后，获得近场地面运动水平向的峰值加速度PGA、峰值速度PGV及周期为0.2，1，2，3，5和10 s的加速度反应谱数据，并与美国NGA-West2的地震动预测模型相比较，研究熊本地震地表和井下地震动峰值及反应谱的衰减特征，通过比较KiK-net台站地表与井下记录结果，探讨浅层场地放大效应的影响。研究结果表明:① 对于井下观测结果，NGA-West2的地震动模型对PGA和短周期0.2 s的反应谱的预测值与井下观测值相比整体偏高，而PGV和较长周期地震动（如1，2和3 s的反应谱）的预测值与井下观测值较为吻合；② 地表观测记录的PGA，PGV和周期为0.2—3 s的反应谱残差整体上随vS30对数值的增大呈线性减小的趋势，而周期为5 s和10 s的长周期部分，其场地效应的影响很小；③ 相对于井下记录，地表记录的地震动PGA，PGV和周期为0.2，1和2 s的反应谱有明显的放大，这种放大作用随浅层场地剪切波速的增大而减小；周期为3，5和10 s时长周期地震动的放大效应很小。 相似文献
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为研究土-结构相互作用(soil-structure-interaction, SSI)对自复位结构体系延性需求谱的影响规律，建立了土-自复位结构的数值分析模型，其中上部结构采用旗帜形单自由度滞回系统模拟，并基于锥模型概念模拟土-基础动力相互作用。选取40条Ⅲ类场地远场地震动记录对SSI系统进行非线性时程分析，讨论了刚性地基结构的周期T、强度折减系数R、结构-土体刚度比a0、结构高宽比s、屈服后刚度比α和耗能系数β对结构延性需求的影响规律。研究结果表明：忽略SSI效应会低估自复位结构的延性需求；对于考虑SSI效应的单自由度自复位结构，延性系数μ与R、a0的相关性较强，且μ与R和a0呈正相关，提高R或a0会增大结构延性需求；延性系数μ与屈服后刚度比α、耗能系数β及结构高宽比s的相关性较弱，其中μ与α和β呈负相关，提高α或β会减小结构延性需求，且随着a0的增大，α和β对延性需求谱的影响越大；当a0=1时，s对延性需求谱基本无影响，而a0取... 相似文献
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收集天津地区十多年来的83份地震安全性评价报告,统计202个钻孔的1 650组动三轴数据,分别给出不同种类土在不同区间深度下的统计代表值及其标准差。以某典型Ⅲ类场地为例,用等效线性化方法进行多种地震动强度及相位输入下的水平成层场地地震反应分析计算,详细研究该地区覆盖土层动剪模量比和阻尼比变异性对地表峰值加速度及其反应谱的影响。结果表明:场地地表峰值加速度和反应谱随土动剪切模量比增大或减小而增大或减小,随土动阻尼比增大或减小而减小或增大;在大震输入条件下,地表峰值加速度和地表反应谱的中、高频段随土动剪切模量比减小而减小的变化尤为明显,动阻尼比变化也有一定影响,但不如土动剪切模量比减小变化时影响明显;在中震、小震地震动输入条件下,场地土的动剪模量比和阻尼比变异性对地表峰值加速度和反应谱影响并不显著。 相似文献
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文中基于某核电站场地工程地质资料,构建了5个硬夹层厚度不同的工程地质剖面。在此基础上,建立了5个一维分析模型,并应用一维土层地震反应等效线性化方法分析了硬夹层厚度对场地地震反应加速度峰值与反应谱的影响。分析结果表明:硬夹层的厚度对场地地震反应峰值加速度与反应谱有较明显的影响,硬夹层厚度的增加减小了场地的非线性效应;不同输入地震动水平下,硬夹层顶板的峰值加速度均小于输入加速度峰值,地表峰值加速度均大于输入加速度峰值;相同输入地震动水平下,随着硬夹层厚度的增加,硬夹层顶板和场地地表峰值加速度与输入峰值加速度之比均表现为先逐渐减小后逐渐增加的趋势,而场地地表与硬夹层顶板的峰值加速度之比随硬夹层厚度的增加总体逐渐增加;硬夹层厚度相同时,随着输入峰值加速度的增大,硬夹层顶板和场地地表的峰值加速度与输入峰值加速度之比逐渐减小;硬夹层仅对一定频带内的加速度反应谱有影响,其厚度越大,影响频带越宽,而对于影响频带之外的加速度反应谱影响很小,同时周期越长影响越小。 相似文献
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采用有限元有限差分方法，结合人工透射边界理论，研究局部坡地地形对地震动特性的影响，分析坡高、坡角对地形放大效应的影响。研究结果表明:坡地地形斜坡段各点反应谱谱比最大值沿坡高逐渐增大，坡脚点对地震动反应谱谱比呈缩小效应；坡底段各点反应谱谱比接近1；坡起平台段空间点受地形效应的影响较大；坡高和坡角对地形效应的影响较明显，当坡角不变时，不同坡高反应谱谱比曲线形状基本相同，峰值点对应的特征周期随着坡高的增加呈增长趋势，峰值点对应的反应谱谱比随着坡高的增加呈增大趋势，斜坡顶点阿里亚斯烈度比值在地形坡高超过一定数值后随着坡高的增加呈增大趋势；当坡高不变时，大部分频段内反应谱谱比最大值随着坡角的增加逐渐增大，斜坡顶点阿里亚斯烈度比值在坡角达到一定数值后随着坡角的增加呈增大趋势。 相似文献
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考虑场地类别与设计分组的延性需求谱和弹塑性位移反应谱 总被引：46，自引：13，他引：33
非线性反应谱是基于性能的抗震设计理论中亟待解决的基础性课题之一。本文将四种场地类别上的641条地震记录,按我国现行抗震规范设计分组的要求分为12组,对大量具有不同屈服强度系数的单自由度体系作了弹塑性时程分析。研究了结构强度水平、周期、场地类别以及设计分组等因素对延性需求的影响。结果表明,在给定屈服强度水平下结构的延性需求强烈地依赖于场地条件、设计分组等因素。对于短周期结构,延性需求随场地土变软而增大,同类场地随设计分组特征周期增大而增大。通过非线性回归分析,建立了与场地类别、设计分组相对应的延性需求谱μ-ξy-T的计算公式。在此公式的基础上,结合现阶段抗震设计规范构建了弹塑性位移反应谱,可用于结构弹塑性位移需求的简化计算,同时讨论了弹塑性位移反应谱的基本特点。 相似文献
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A set of reinforced concrete structures with gravitational loads and mechanical properties (strength and stiffness) representative of systems designed for earthquake resistance in accordance with current criteria and methods is selected to study the influence of dynamic soil–structure interaction on seismic response, ductility demands and reliability levels. The buildings are considered located at soft soil sites in the Valley of Mexico and subjected to ground motion time histories simulated in accordance with characteristic parameters of the maximum probable earthquake likely to occur during the system's expected life. For the near‐resonance condition the effects of soil–structure interaction on the ductility demands depend mainly on radiation damping. According to the geometry of the structures studied this damping is strongly correlated with the aspect ratio, obtained by dividing the building height by its width. In this way, for structures with aspect ratio greater than 1.4 the storey and global ductility demands increase with respect to those obtained with the same structures but on rigid base, while for structures with aspect ratio less than 1.4 the ductility demands decrease with respect to those for the structures on rigid base. For the cases when the fundamental period of the structure has values very different from the dominant ground period, soil–structure interaction leads in all cases to a reduction of the ductility demands, independently of the aspect ratio. The reliability index β is obtained as a function of the base shear ratio and of the seismic intensity acting on the nonlinear systems subjected to the simulated motions. The resulting reliability functions are very similar for systems on rigid or on flexible foundation, provided that in the latter case the base rotation and the lateral displacement are removed from the total response of the system. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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A one-dimensional equivalent linear method (EQL) is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent. However, historical earthquake records and laboratory test results indicate that nonlinear soil behavior is frequency-dependent. Several frequency-dependent equivalent linear methods (FDEQL) related to the Fourier amplitude of shear strain time history have been developed to take into account the frequency-dependent soil behavior. Furthermore, the shear strain threshold plays an important role in soil behavior. For shear strains below the elastic shear strain threshold, soil behaves essentially as a linear elastic material. To consider the effect of elastic-shear-strain-threshold- and frequency-dependent soil behavior on wave propagation, the shear-strain-threshold- and frequency-dependent equivalent linear method (TFDEQL) is proposed. A series of analyses is implemented for EQL, FDEQL, and TFDEQL methods. Results show that elastic-shear-strain-threshold- and frequency-dependent soil behavior plays a great influence on the computed site response, especially for the high-frequency band. Also, the effect of elastic-strain-threshold- and frequency-dependent soil behavior on the site response is analyzed from relatively weak to strong input motion, and results show that the effect is more pronounced as input motion goes from weak to strong. 相似文献
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Deamplification of strong motion and the increase of the effective period of soil deposits are typical nonlinear effects; we seek them in SMART1-array data by applying the horizontal-to-vertical spectral ratio (HVSR) technique. The recordings, from four soil and one rock stations, represent 23 earthquakes (ML 4.9–7.0); PGA varies between 20–260 cm/s2. For each station, mean HVSR curves are calculated for two PGA ranges: <75 cm/s2 and >100 cm/s2 (weak and strong motion). At the soil stations, the “weak” (linear) and “strong” (nonlinear) responses are significantly different. Below 1–1.8 Hz, the nonlinear response exceeds the linear one. Above 2 Hz, the nonlinear response drops below the linear one and above 4–6 Hz below unity (deamplification). From 10 to 16 Hz, the two responses converge. One soil site shows significant negative correlation between resonance frequency and ground acceleration. Such behaviour agrees with other empirical studies and theoretical predictions. Our results imply that the HVSR technique is sensitive to ground-motion intensity and can be used to detect and study nonlinear site response. 相似文献
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Chien-Ping Lee Yi-Ben Tsai Kuo-Liang Wen 《Soil Dynamics and Earthquake Engineering》2006,26(5):435-460
Both linear and nonlinear behaviors of soil deposits were evaluated by strong and weak motion data observed on the surface and at depths of 6, 11, 17, 47 m at the Large Scale Seismic Test (LSST) array in Lotung, Taiwan. The soil properties measured by well logging and by the shear wave velocity profile measured by uphole and cross-hole methods are available. Both one-dimensional equivalent-linear method and nonlinear method are used for the evaluation have been used. The synthetic records at various depths are obtained by using the records at the bottom as input motion. These synthetic records are then compared with actual records at corresponding depths. Records of 13 earthquakes are used. We find that the synthetic records obtained from a linear model match well with actual records for small input motions, but the results obtained from a nonlinear model match poorly. On the other hand, the synthetic records using both the nonlinear model and equivalent-linear model are in good agreement with the observed records for large input motions. In these cases, the predicted response spectra using the linear model consistently overestimate the observed records. The threshold distinguishing the large and small input motions is 0.04 g at depth of 47 m for the LSST data. Thus, the nonlinearity started at 0.04 g and occurred unequivocally at 0.075 g. Furthermore, the dominant frequencies shift toward lower values when input motions become large. Clearly, the observed records at the LSST site manifest nonlinearity of soil response. The hysteresis loops evaluated by the nonlinear method show a permanent strain of about 0.01% in soil layers at higher ground motion input levels in this case. 相似文献
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在地震荷载作用下,自由场地会产生土体侧向变形和地表响应放大现象。由于土体的高度非线性,计算自由场地地震响应时,不同的阻尼比及剪切模量取值是造成其计算结果与试验结果相差较大的原因之一。目前动力计算常采用瑞利阻尼方法,其系数取值会在一定程度上影响计算结果。选用两模态简化瑞利阻尼系数计算方法,分析土体阻尼比及控制频率的取值对计算结果的影响,对比离心机模型试验,利用开源有限元平台OpenSees,采用适合于土体动力分析的多屈服面本构模型(PDMY),建立剪切梁模型模拟三维自由场地,并分析瑞利阻尼参数对自由场地地震响应和侧向变形计算结果的影响。结果表明,针对相对密度为60%的Nevada干砂,阻尼比为4%、控制频率比为5时,场地响应计算结果与试验结果较为符合。综合分析显示场地非线性响应时域计算时,应特别注意选用的瑞利阻尼参数值。 相似文献
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INTRODUCTION ThetrainferryharboratSitudiinYantaiisakeytransportationinfrastructurewhichlinks NortheastChinaandSouthChinainthecoastalarea.Topographically,theengineeringsiteislocated inacoastalplainandthereliefisflatandcoveredwithathicksoilstratumwhichiscom… 相似文献
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为研究强震区跨断层桥梁桩基非线性动力相互作用特性,依托海文大桥实体工程,利用MIDAS/GTS有限元软件,建立了桩-土-断层相互作用模型,分析0.20~0.60g地震动强度下断层上下盘桩基加速度响应、桩顶水平位移、桩身弯矩以及桩身剪力响应情况。结果表明:覆盖层土体对桩身加速度放大作用明显,且随着输入地震动强度的增大,放大作用逐渐减弱;覆盖层对地震波的滤波作用显著,随着输入地震动强度的增大,滤波作用逐渐减弱;上盘桩基达到桩顶峰值加速度的时刻滞后于下盘;随着输入地震动强度的增大,上、下盘桩的桩顶产生的永久位移和水平位移峰值逐渐变大,上盘桩顶产生的永久位移和桩顶峰值位移均大于下盘,产生显著的"上盘效应";不同强度地震动作用下,断层上、下盘桩基弯矩均在上部土层界面处达到峰值,剪力均在基岩面处达到峰值,下盘桩基弯矩和剪力峰值大于上盘桩基,呈现出显著的"下盘效应"。在桥梁桩基抗震设计时,应着重考虑断层上、下盘桩基的差异和不同强度地震作用对桩基承载特性的影响。 相似文献