黄土场地地铁车站振动台试验方案设计与研究

为得到可靠的试验数据,对黄土场地典型断面地铁车站大型振动台试验方案进行设计与研究。根据试验目的和特点,提出黄土场地与地铁车站动力相互作用模型体系相似设计原则,并基于Bockingham的π定理对模型结构进行相似设计;通过室内试验研究模型材料配合比、力学特性及模型制作技术;采用有限元-无限元耦合数值建模方法,分析黄土场地地铁车站地震响应,基于数值模拟结果对振动台试验中的传感器布设方案进行研究;根据西安及周边地区地震环境特点,确定振动台试验输入地震动与加载方案。研究结果表明,试验模型结构宏观震害与数值模拟结果较吻合。本研究可为黄土场地地铁车站、地铁隧道及地下商业街等地下结构振动台试验方案设计与深入研究提供参考。     

正弦荷载的不同输入角度对非对称结构的转动影响

近十年来,地震动转动分量已成为国际性的研究热点,目前主要进行理论分析、数值模拟与试验研究.由于地震时引起刚体发生转动的原因非常复杂,涉及到局部场地条件等影响因素,再加上严重缺乏地震转动分量的记录,对震后刚体翻转现象及其数值模拟和试验研究变得非常重要.     

门源MS6.9地震中大梁隧道地震动响应分析

2022年1月8日,青海省门源县发生M_S6.9地震,造成震中附近的兰新高铁大梁隧道受损,导致高铁长时停运。文章通过建立二维平面应变模型,加载双向门源波进行动力时程分析,得到了大梁隧道的地震动响应结果,并对模型在震后的受力变形及震害特征进行详细分析。结果表明：在门源波双向加载下,大梁隧道的地震动响应受水平地震荷载影响很大;沿着y轴正向,隧道的截面形状对纵向位移和加速度的地震动响应有加强作用;拱顶处地震动响应最大,其竖向及横向地震动响应加速度分别为5.206 4 m/s²、4.534 8 m/s²,竖向及横向位移分别为7.070 9 cm、0.641 5 cm;拱底处地震动响应最小,其竖向及横向地震动响应加速度分别为3.287 6 m/s²、4.511 2 m/s²,竖向及横向位移分别为4.851 6 cm、0.625 2 cm;拱肩、拱脚处存在明显的应力集中现象,拱顶、拱底、拱肩及拱脚处内力的受力形式发生变化,但是衬砌应力和内力的极值均发生在拱腰及拱脚处,说明拱腰及拱脚处为震害严...     

考虑地震动持时的液化场地-桩基振动台试验设计

振动台试验中地震动输入是一个关键因素,地震动持时压缩是1-G振动台试验设计中的重要环节,地震动持时压缩后,地震动特性发生改变,对地基-结构体系动力响应产生显著影响。为了研究振动台试验中地震动输入特性,特别是地震动持时压缩对可液化场地-结构体系地震非线性动力响应的影响,本论文较系统地阐述了振动台试验的整体设计思路,其中重点阐述了相似比设计思路及持时压缩方法、模型地基及结构制备、叠层剪切型模型箱性能、传感器布设及新型传感技术、持时压缩后地震动特性的变化、数据处理方法。成套方案设计思路为振动台试验提供了完备、科学的方法。     

超大冷却塔欠质量模型振动台试验研究

抗震研究中模型试验起着重要的作用。应用相似理论对超大冷却塔进行了欠质量试验模型设计,介绍了缩尺模型的特殊施工工艺,根据地震动三要素确定12条地震动用于冷却塔试验模型地震动输入,对超大冷却塔1∶30的模型在5m×5m的震动台上进行了试验。试验测试了超大冷却塔的自振频率,利用振动台模拟7度、8度设防烈度对超大冷塔模型进行了动力试验。应用数值模拟分析了冷却塔试验模型的地震效应,对比了试验测试结果与数值模拟分析结果,数值模拟分析结果与试验结果吻合较好。试验结果与分析结果表明,冷却塔有较宽的频率带宽。时程分析解与试验结果对比表明,采取梁柱模型分析超大冷却塔能很好地模拟冷却塔的动力特性。     

横向非一致地震激励下埋地管道的动力响应分析

为研究埋地管道在地震激励时管-土相互作用的动力响应问题,研发双向层状剪切连续体模型土箱,建立管G土相互作用有限元分析模型,对横向非一致地震激励下埋地管道地震响应进行数值模拟分析,并与试验结果进行对比.结果表明:数值模拟和振动台试验结果中的管道应变峰值均呈现出沿管道中间大两端小的现象,管道中间应变峰值最小达到两端的1．6倍左右;管道加速度、 土体加速度峰值均随着加载等级的提高而增大,涨幅愈加明显,多峰频率由0~10Hz逐渐向10~ 20Hz频域扩散,管道运动更为自由;土体位移随着加载等级的提高呈现逐级增大的现象,在加载等级增加到0．4g 时位移曲线斜率减小,土体非线性表现明显.数值模拟和振动台试验对比分析的结论表明数值模拟分析的合理性和试验结果的可靠性,为研究横向非一致激励对埋地管道地震响应的影响提供了依据.     

混凝土框架-钢柱阀厅结构振动台试验研究

本文对混凝土框架-钢柱换流站阀厅结构进行了地震模拟振动台试验.根据原型结构特点及试验室现有条件设计和制作了1/8满配重模型缩尺模型,选定了三种适用于不同场地类别的地震动进行逐级加载,在每级地震动加载前后,均对结构进行了白噪声输入.研究了阀厅结构地震响应(包括加速度放大系数、索的动拉力等)、结构固有频率变化、结构阻尼比和...     

横向非一致激励下土层地震响应的振动台模型试验研究

针对自由场土体的非线性地震响应问题,采用悬挂式连续体模型箱,开展了横向一致激励和非一致激励下砂土自由场土体的振动台试验。通过试验,研究了不同地震动、不同地震强度作用下自由场土体的地震动反应特性及其变化规律,包括场地土体的动力特性、加速度地震响应、剪应力-剪应变以及土体的沉降。研究结果表明:土体的非线性发展程度不仅与地震动记录有关,还与地震动输入方式、加载等级有关;与一致激励相比,非一致激励下土体运动的不一致性引起了更强的土体结构性变化,频率降低,阻尼比增大,土体的加速度峰值和频谱峰值均有降低,土体的非线性发展相对较快。土体剪应力-剪应变曲线和沉降曲线的变化规律一定程度上也反映了土体的塑性发展情况,所得结论和自由场地震反应宏观现象一致,彼此佐证了结论的合理性。     

含弱渗透性覆盖层饱和砂土地震液化特性研究

针对含弱渗透性覆盖层的饱和砂土地基进行一组离心机振动台试验,并采用OpenSees对试验模型进行数值模拟。通过模型试验与数值模拟结果对比讨论OpenSees对于饱和砂土地基地震液化模拟的精度;采用水平方向的Arias强度表示传入某一位置的地震动强度,并以液化时水平方向Arias强度作为该土层的抗液化强度;采用OpenSees计算不同地震动输入时饱和砂土的反应,以此检验Arias强度作为抗液化强度的准确性。结果表明,引起饱和砂土液化所需要的地震动强度随深度增加而增加;当传入的地震强度达到砂土发生液化所需要的地震强度时,该层砂土将会发生液化。     

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。     

Torsional phenomena in 2008 great Wenchuan earthquake

It is well known that there are some torsional damages in earthquakes. In Taibai park, Jiangyou city, Sichuan province, most of the stone statues, which were placed upon the banisters of one zigzag bridge, exhibited different torsional phenomena in 2008 Wenchuan earthquake. This paper introduces the torsional phenomena of all the statues on the zigzag bridge firstly. Then one eccentricity model is established and the equivalent rotational accelerations are calculated in order to analyze the causes of the to...     

Shake table testing of an elevator system in a full‐scale five‐story building

This paper investigates the seismic performance of a functional traction elevator as part of a full‐scale five‐story building shake table test program. The test building was subjected to a suite of earthquake input motions of increasing intensity, first while the building was isolated at its base and subsequently while it was fixed to the shake table platen. In addition, low‐amplitude white noise base excitation tests were conducted while the elevator system was placed in three different configurations, namely, by varying the vertical location of its cabin and counterweight, to study the acceleration amplifications of the elevator components due to dynamic excitations. During the earthquake tests, detailed observation of the physical damage and operability of the elevator as well as its measured response are reported. Although the cabin and counterweight sustained large accelerations because of impact during these tests, the use of well‐restrained guide shoes demonstrated its effectiveness in preventing the cabin and counterweight from derailment during high‐intensity earthquake shaking. However, differential displacements induced by the building imposed undesirable distortion of the elevator components and their surrounding support structure, which caused damage and inoperability of the elevator doors. It is recommended that these aspects be explicitly considered in elevator seismic design. Copyright © 2016 John Wiley & Sons, Ltd.     

地震作用下核电站环行吊车动力响应的模型实验研究

基于量纲分析理论,提出地震作用下环行吊车缩尺模型动力响应的相似准则,确定核环吊原型和实验模型之间动力响应的相似关系。根据抗震规范要求和相似准则,采用El Centro 1979地震波作为实验台地震输入,对振动台震动输入进行调幅处理,水平地震输入幅值为0.3g,竖向地震输入幅值为0.2g,地震输入的时间缩尺为4。核环吊抗震实验结果表明,与实验台地震输入峰值相对比,吊车大梁跨中水平加速度峰值增加了56.0%,跨中竖向的加速度峰值增加了119.0%;环轨水平加速度峰值增加了66.7%,环轨竖向的加速度峰值增加了43.5%。研究表明,当水平地震波的输入方向与吊车大梁轴线相垂直时,吊车大梁跨中水平加速度峰值最大;当水平地震波的输入方向与吊车大梁轴线相平行时,环轨的水平加速度峰值最大;环轨的垂直加速度峰值受水平地震波的输入方向影响不显著。在地震荷载作用下,核环吊没有发生跳轨现象。     

Investigation of effect of near-fault motions on substandard bridge structures

The objective of this study was to investigate the effects of near-fault ground motions on substandard bridge columns and piers. To accomplish these goals, several large scale reinforced concrete models were constructed and tested on a shake table using near- and far-field ground motion records. Because the input earthquakes for the test models had different characteristics, three different measures were used to evaluate the effect of the input earthquake. These measures are peak shake table acceleration, spectral acceleration at the fundamental period of the test specimens, and the specimen drift ratios. For each measure, force-displacement relationships, strains, curvatures, drift ratios, and visual damage were evaluated. Results showed that regardless of the measure of input or response, the near-fault record generally led to larger strains, curvatures, and drift ratios. Furthermore, residual displacements were small compared to those for columns meeting current seismic code requirements.     

Shake table tests of a new steel–asphalt composite layer system for the seismic base isolation of housing units

Base isolation is an effective way to reduce earthquake energy transfer from ground to structure, but existing seismic isolation systems are not very suitable for rural buildings for some reasons. A new steel–asphalt composite layer for the seismic base isolation of housing units is present in this paper. Its dynamic characteristics and isolation effect are studied by shake table tests of two full-scale specimens. Different earthquake waves with different peak ground accelerations (PGA, from 0.1 g to 0.4 g) are input. Test results show that the isolation layer could efficiently reduce the input acceleration. Moreover, as the PGA increase, the isolation layer shows good function of the displacement limit.     

Shake table test of soil-pile groups-bridge structure interaction in liquefiable ground

<正>This paper describes a shake table test study on the seismic response of low-cap pile groups and a bridge structure in liquefiable ground.The soil profile,contained in a large-scale laminar shear box,consisted of a horizontally saturated sand layer overlaid with a silty clay layer,with the simulated low-cap pile groups embedded.The container was excited in three E1 Centra earthquake events of different levels.Test results indicate that excessive pore pressure(EPP) during slight shaking only slightly accumulated,and the accumulation mainly occurred during strong shaking.The EPP was gradually enhanced as the amplitude and duration of the input acceleration increased.The acceleration response of the sand was remarkably influenced by soil liquefaction.As soil liquefaction occurred,the peak sand displacement gradually lagged behind the input acceleration;meanwhile,the sand displacement exhibited an increasing effect on the bending moment of the pile,and acceleration responses of the pile and the sand layer gradually changed from decreasing to increasing in the vertical direction from the bottom to the top.A jump variation of the bending moment on the pile was observed near the soil interface in all three input earthquake events.It is thought that the shake table tests could provide the groundwork for further seismic performance studies of low-cap pile groups used in bridges located on liquefiable groun.     

大型地下洞室群地震水平加速度传播特征研究

考虑了高山峡谷基岩场地的深度衰减效应,假设地震危险性分析提供的水平峰值加速度的所在位置,选用攀枝花—会理地震波,通过基线校正和高频滤波作为实际地震动输入,利用FLAC3D软件对某水电站大型地下洞室群进行了地震水平加速度传播特性的研究。数值分析结果表明,厂房周围监测点水平加速度时程和输入地震水平加速度时程相似,但存在0.08～0.12s的滞后时差,输入地震动水平峰值加速度向上传播时具有放大效应,在洞室群附近放大两倍左右。所得结果对大型地下洞室群地震动传播特征问题研究具有一定的参考意义。     

地震动参数对斜坡加速度动力响应规律的影响

2008年‘5.12’汶川大地震诱发斜坡地质灾害在空间分布上表现出了明显的高程效应和岩性效应。本文采用上硬下软和上软下硬两种典型岩性组合斜坡模型,完成了1:100比尺的振动台试验。文中重点分析了地震波类型(频谱)、激振方向和地震动三参数对斜坡模型水平向加速度动力响应规律的影响。分析结果表明:(1)水平单向激振时,15Hz正弦波和汶川地震波作用下的高程放大效应主要体现在斜坡模型中上段,两者在上软下硬组合斜坡模型中产生了近乎相同的水平向加速度动力响应规律,原因主要在于两者的卓越频率接近。(2)模型对合成向汶川地震波的放大作用依次超过单向水平向和竖直向汶川波的作用,且合成向与水平单向汶川地震波的作用规律基本相同。(3)随着振动强度增加,模型对低频波的放大作用增强。(4)在合成向汶川地震动作用下,随着振动强度增加,模型各高程处的水平向加速度峰值(PGA)逐渐增加,其相应的放大系数在模型中上段逐渐降低至2.0以下,最终趋于平缓,表明模型沿高程向的放大效应逐渐减弱。此外,各参数对模型的水平向加速度响应因模型自身的岩性组合结构而异,随着振动强度增加,上硬下软斜坡模型中上部的水平向速度响应值基本保持在1.0～2.7倍于上软下硬斜坡模型中上部的水平向加速度响应值这一水平。     

Experimental verification of torsional response control of asymmetric buildings using MR dampers

This paper proposes a semiactive control system to reduce the coupled lateral and torsional motions in asymmetric buildings subjected to horizontal seismic excitations. Magnetorheological (MR) dampers are applied as semiactive control devices and the control input determination is based on a clipped‐optimal control algorithm which uses absolute acceleration feedback. The performance of this method is studied experimentally using a 2‐story building model with an asymmetric stiffness distribution. An automated system identification methodology is implemented to develop a control‐oriented model which has the natural frequencies observed in the experimental system. The parameters for the MR damper model are identified using experimental data to develop an integrated model of the structure and MR dampers. To demonstrate the performance of this control system on the experimental structure, a shake table is used to reproduce an El Centro 1940 N–S earthquake as well as a random white noise excitation. The responses for the proposed control system are compared to those of passive control cases in which a constant voltage is applied to the MR damper. Copyright © 2003 John Wiley & Sons, Ltd.     

Continuous estimates on the earthquake early warning magnitude by use of the near-field acceleration records

In this article, the seismic records of Japan’s Kik-net are selected to measure the acceleration, displacement, and effective peak acceleration of each seismic record within a certain time after P wave, then a continuous estimation is given on earthquake early warning magnitude through statistical analysis method, and Wenchuan earthquake record is utilized to check the method. The results show that the reliability of earthquake early warning magnitude continuously increases with the increase of the seismic information, the biggest residual happens if the acceleration is adopted to fit earthquake magnitude, which may be caused by rich high-frequency components and large dispersion of peak value in acceleration record, the influence caused by the high-frequency components can be effectively reduced if the effective peak acceleration and peak displacement is adopted, it is estimated that the dispersion of earthquake magnitude obviously reduces, but it is easy for peak displacement to be affected by long-period drifting. In various components, the residual enlargement phenomenon at vertical direction is almost unobvious, thus it is recommended in this article that the effective peak acceleration at vertical direction is preferred to estimate earthquake early warning magnitude. Through adopting Wenchuan strong earthquake record to check the method mentioned in this article, it is found that this method can be used to quickly, stably, and accurately estimate the early warning magnitude of this earthquake, which shows that this method is completely applicable for earthquake early warning.