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1.
地震波是一种随机的、不规则作用的动荷载脉冲,可分为振动型和冲击型。不同类型的地震波会对砂土液化和变形等产生重要影响,而传统的砂土震陷计算方法往往忽视这种因素,只考虑最大加速度幅值。通过编写UMAT子程序,在非线性有限元软件ABAQUS中开发亚塑性砂土边界面模型,对不同地震波类型下不同相对密度的砂土进行动单剪试验模拟,得到一系列砂土剪应变及竖向应变的时程曲线,并与室内试验结果进行对比分析。研究表明:在同一工况下,同类型的地震波引起的砂土竖向应变相近,不同类型引起的竖向应变差异明显;振动型地震波比冲击型引起的竖向应变更大。 相似文献
2.
In China, The Yellow River delta is the youngest large river delta, and the low liquid limit alluvial silt is widely distributed there. The silt is easy to liquefy so that the silt subsoil shows large settlement under traffic load. At present, few in situ model tests were conducted to study the traffic-load-induced settlement of silt subsoil. Therefore, a falling-weight simulation equipment of traffic load was developed. By adjusting the technical parameters such as the falling height of the weight, different types of traffic loads can be well simulated. With the equipment, in situ tests were carried out to study cumulative settlement of silt subsoil in the Yellow River delta. Tests indicate that the settlement and excess pore water pressures rapidly grow initially and then tend to be stable with increasing the number of load cycles, and they also increase with the magnitude of the traffic load. When the load attains a threshold value, liquefaction takes place in the silt subsoil. After terminating loading, the pore water pressure rapidly decreases and the settlement increases simultaneously, while after one hour they tend to stabilize. Based on Chai–Miura cumulative deformation model of soil, the traffic-load-induced cumulative settlement of silt subsoil was calculated and compared with the test results. The calculated cumulative settlement with increasing number of load cycles agrees well with the test results, except the initial phase of cyclic loading where the settlement observed in the situ tests is overestimated. This is mainly because Chai–Miura model assumes undrained conditions while the subsoil under traffic loads is partly drained. 相似文献
3.
以甘肃兰州地铁一号线某地铁车站为工程背景,基于ADINA分析软件32CPU有限元显式计算平台,建立地基土与车站结构相互作用的非线性地震响应计算模型。数值分析在El-Centro、Kobe和兰州波的多遇地震条件下其车站及地基土的动力响应差异。结果表明:车站结构振型与周围地基土振型基本一致;车站底板、中板及顶板的加速度时程曲线形状基本相同;中柱和侧墙均随着埋深的增加其水平位移减小;车站周围的地表土体均发生了不同程度的沉降,其距车站7.5m范围的沉降尤为显著,致使周围建筑物会遭受到一定程度的损坏。 相似文献
4.
高层建筑物在地震作用下易出现倒塌状况，严重影响人身安全，因此高层建筑物地震安全防护距离的预测至关重要。设计以基础数据库为核心的高层建筑物地震安全防护距离预测系统，通过高层建筑物基本信息系统采集高层建筑物高度、宽度、结构类型等基本数据信息，并将这些信息存储到震害数据库系统中；地震危害模型分析系统依据数据库系统中存储的这些建筑物基本信息，分析地震危险性后，通过研究地震时高层建筑上部结构水平、底部及顶部先接触地面三种落地状态情况下，计算得到薄弱层和薄弱层上部结构高度的安全防护距离。实验验证在人工地震波作用下，利用该预测系统可有效获取实验小区高层建筑物的安全防护距离界定示意图，且其能够准确分析地震作用下高层建筑物晃动时"飞石"安全距离，以及三种地震波作用下建筑物地震安全防护距离分布规律和主要影响范围，其预测效果好。 相似文献
5.
结合某沉管隧道沉管段基槽开挖工程,采用爆破动态效应的现场测试、理论分析等综合手段,探索水下爆破水中冲击波和爆破地震波动对邻近建筑物的动态效应特性。研究表明:(1)与地震波的峰值压力值相比,浅水条件下钻孔爆破水中冲击波压力值较小,传播速度也没有地震波快,特定情况下,在考量岸边堤岸及岸边建筑物的稳定性时可以忽略水冲击波的影响;(2)对于不同区域爆破施工来说,应根据其距离被保护对象的远近,选择各允许最大药量中的最小值作为最大爆破控制药量。研究成果对类似工程具有一定的借鉴意义。 相似文献
6.
为优化处于长周期地震动输入下的大型建筑剪力墙结构,进行了振动台试验。分析普通地震动与长周期地震动波的区别,证明了长周期地震波具有显著长周期分量的特性。将某一高层酒店剪力墙作为研究案例,设计模拟实验台的构建流程与传感器布局,将建筑模型缩尺比例设置为1∶10。选择CA波、RG波、EL波作为实验用地震波,从位移与结构周期、层间剪力与位移比、易损性以及损失评估等方面对大型建筑剪力墙的抗震性能进行了评估。振动台试验结果表明,在位移相同的情况下,长周期地震波下的建筑极限承载力最小;在经历CA波、RG波、EL波后,模型的自振周期均发生变化,而EL波作用下模型的自振周期始终比基本周期略长;不同地震波下,X、Y向层间剪力变化基本趋于一致;CA波、EL波作用下,X向位移比较为接近,而剪力墙Y向上位移比在三种地震波作用下具有较大差异性;在长周期地震波作用下,大型建筑剪力墙损伤最为严重。 相似文献
7.
Nonlinear dynamic response of r.c. framed structures subjected to near-fault ground motions 总被引：2，自引：1，他引：1
The nonlinear dynamic response of reinforced concrete (r.c.) framed buildings subjected to near-fault ground motions is studied
to check the effectiveness of current code provisions with reference to study cases. Three-, six- and twelve-storey r.c. plane
frames, representative of symmetric framed buildings, are designed according to the European seismic code (EC8), assuming
medium and high ductility classes and stratigraphic profiles A (rock) and D (soft soil) in a high-risk seismic region. The
nonlinear seismic analysis is performed using a step-by-step procedure; a bilinear model idealizes the behaviour of the r.c.
frame members. Artificially generated motions (matching EC8 response spectra for subsoil classes A and D) and horizontal motions
(recorded on rock- and soft soil-site at near-fault areas) are considered. The results indicate that near-fault ground motions
may require a special consideration in the code, in particular when designing r.c. framed structures placed on a soft soil-site;
particular attention should be paid to the design of the frame members of the lower storeys. 相似文献
8.
The use of the standing wave method to study seismically insulated buildings is substantiated. For two buildings of interest with different types of seismic protection (a “flexible” floor and rubber base insulators), the total field of standing waves is studied in detail. Effects that raise doubts about the reliability of seismic protection are found. Estimation of the role of nonlinear vibrations in standing waves has made it possible to establish that weak nonlinearity is recorded at high-frequency modes at small vibration amplitudes, due to discordant vibrations of the building components. The data obtained by the standing wave method are recommended for verifying models used to calculate seismic insulation of buildings. 相似文献
9.
In performance-based geotechnical earthquake engineering, the required degree and spatial extent of ground densification for mitigation of liquefaction beneath a structure should be determined based on the acceptable levels of performance of foundation. Currently, there is no solution for evaluation of the amount of settlement and tilt of footings constructed on a densified ground which is surrounded by a liquefiable soil. This implies the need for numerical procedures for simulation of seismic behavior of shallow foundations supported on both liquefiable and densified subsoil. In this paper, the dynamic response of shallow foundations on a densified ground is studied using a 3D fully coupled dynamic analysis. For verification of the numerical model, simulation of a series of centrifuge experiments has been carried out and the results were compared with the experimental measurements. After verification of the numerical model, a comprehensive parametric study has been performed to develop a methodology for estimating the effectiveness of subsoil densification in reducing liquefaction-induced settlement of shallow foundations. Range of problem variables were considered in a way that the possibility of bearing capacity failure is low enough. The proposed methodology can be utilized for development of a performance-based design procedure for liquefaction hazard mitigation by soil densification. 相似文献
10.
为对具有传统文化的仿古建筑在不破坏其原有建筑风貌的基础上进行抗震加固,将隔震技术应用于仿古建筑。采用数值模拟的方法研究仿古建筑隔震,建立隔震与非隔震两种有限元计算分析模型,并对加固前、后模型进行动力时程分析。通过输入不同频谱的El Centro Site波、Taft波和RH1TG055波,对比分析两种模型在地震作用下的位移、加速度时程曲线。结果表明：采用隔震技术加固方案后,结构的地震响应得到明显的降低,从而显著地提高了结构的抗震能力。利用该方法加固,节约造价,施工方便,可供同类工程参考。 相似文献
11.
爆破地震作用下桩-土-结构相互作用的数值模拟 总被引：1，自引：0，他引：1
土-结构动力相互作用是地震工程和结构抗震的重要研究内容,但目前对爆破地震作用下土-结构动力相互作用的研究较少。运用大型有限元软件ANSYS/LS-DYNA,建立了桩-土-结构相互作用体系的三维有限元模型,由桩尖输入实测爆破地震波,取得了良好的计算效果。计算结果表明：考虑桩-土-结构相互作用后,群桩基础中每个桩的位移、加速度和剪应力幅值均呈桩顶大、桩尖小的倒三角分布,桩与承台的接合部比较容易受到损坏;桩-土-结构相互作用体系在爆破地震波冲击后,还会发生几次振动,但是这些振动产生的影响要小于爆破地震产生的影响,这与实测结果相符合;爆破地震波冲击下,群桩基础中,角桩顶部表面的桩土接触压力较大,但在爆破地震波冲击后,中心桩顶部表面的桩土接触压力较大,且具有一定的周期性,直至衰减为零。 相似文献
12.
A novel method of synthesizing seismic wave using wavelet reconstruction is proposed and compared with the traditional method of using theory of Fourier transform. By adjusting the frequency band energy and taking it as criterion, the formula of synthesizing seismic wave is deduced. Using the design parameters specified in Chinese Seismic Design Code for buildings, seismic waves are synthesized. Moreover, the method of selecting wavelet bases in synthesizing seismic wave and the influence of the damping ratio on synthesizing results are analyzed. The results show that the synthesis seismic waves using wavelet bases can represent the characteristics of the seismic wave as well as the ground characteristic period, and have good time-frequency non-stationary. 相似文献
13.
基于土体的等效粘弹性模型,结合场地典型剖面的土体特性以及室内实验确定的各力学参数,采用时域积分和迭代的方法研究了沁河倒虹吸管道在地震作用下的反应,分析了管道截面中间底部点绝对地震位移、顶部点相对于底部点的地震动位移及管道动静综合主应力的变化规律;并根据有限元时程法的分析结果,按照混凝土承载能力极限状态设计式,对管身混凝土的抗拉、抗压安全度进行校核。结果表明,在人工地震波、调整后的E1 Centro和Pulgas地震波分别输入的情况下沁河渠道倒虹吸管道均满足抗震要求。 相似文献
14.
许多学者对软土在动力作用下的变形特性进行了大量的研究,并提出了相应的经验公式,但其经验公式参数较多且试验复杂,不易被一般工程技术人员掌握运用。本文采用天津滨海地区软土为研究对象,进行钻探取样、波速测试、室内静力学和动三轴试验,获取该地区软土的静、动力学参数,并利用相对简单的模型对残余应变和软化指数随振次的变化规律采用最小二乘法进行拟合,取得很好的效果。成果表明,利用简单的模型对软土的动力特性进行区域性研究是可行的。该成果可为今后软土动力特性和软土震陷计算方法研究提供参考和基础性资料。 相似文献
15.
将参数化建模的方法引入减震结构的分析与设计中，通过预设目标和迭代优化计算，以天水市某高层住宅消能减震结构为例，寻找最优的阻尼器布置方案。为评估和验证该消能减震结构的抗震性能，分别采用Perform 3D和ETABS等软件分析结构在多遇和罕遇地震作用下的结构响应，分析结果表明：小震作用下，消能减震结构的楼层位移、层间位移角、楼层弯矩及楼层剪力均减小6.5%以上，达到了设计要求；大震作用下，结构框架柱、框架梁、剪力墙和阻尼器能够满足既定的性能要求，层间位移角满足规范限值，能够达到“大震不倒”的设计目标，研究结果为实际工程预设减震目标和阻尼器优化布置提供参考。 相似文献
16.
The rapid decrease of the acceleration spectral amplitude at high frequencies has widely been modeled by the spectral decay factor kappa (κ). Usually, the path-corrected component of κ, often called κ0, is believed to be a local and frequency-independent site characteristic, in turn representing attenuation related to waves propagating vertically through the very shallow layers beneath the study site. Despite the known relevance of κ0 in a wide range of seismological applications, most methods for its calculation do not fully consider the influence of the scattering component. To account for the scattering component, we present a summary of statistical observations of the seismic wavefield at sites of the Swiss seismic networks. The intrinsic properties of the wavefield show a clear dependency on the local shallow subsoil conditions with differences in the structural heterogeneity of the shallow subsoil layers producing different scattering regimes. Such deviations from the ballistic behavior (i.e., direct waves that sample only distinct directions) are indicative for local structural heterogeneities and the associated level of scatter. Albeit the attenuation term related to scattering depends nonlinearly on the intrinsic term, the results indicate that the commonly used explanation for the high-frequency decay spectrum might not be appropriate but involving the amount of scattering might allow better constrained estimates of κ0. 相似文献
17.
传统高层建筑地震损伤模型不能反映构件极限滞回耗能随累积幅值的改变情况,无法有效确定组合参数,离散性较大。为此,设计一种远场长周期地震下高层建筑的地震损伤模型。针对不同层次高层建筑结构,依据广义力-广义变形曲线,构建变形损伤模型。结合累积能量比、远场长周期地震瞬时输入能比构建能量损伤模型。从变形与能量两方面综合评价损伤,依据钢筋混凝土结构构建最大反应变形与耗损能量的线性组合地震损伤模型,并对其进行改进。实验选用ILA003、ILA048和TCU115三种长周期地震波,计算不同构件和高层建筑结构整体损伤结果,验证所提模型的可靠性。将所提模型应用于实际高层建筑中,发现其实用性强。 相似文献
18.
近岸水平场地液化侧向大变形影响因素分析 总被引：2，自引：0，他引：2
利用改进的软化模量分析方法,对近岸水平场地液化侧向大变形进行数值计算,以研究地震波波形和幅值大小、液化、竖向地震动对侧向大变形的影响。结果表明:不同的地震波作用下,即使峰值加速度相同,液化程度与侧移距离也可能有较大不同,表现了土体变形的强非线性性质,但大地震下液化导致的侧移几乎都在米的量级上;计算区域中无液化区时,岸壁侧向永久位移很小,在几公分左右,随水平峰值加速度及不同地震动输入改变不大;计算区域中有液化区时,岸壁侧向永久位移显著增大,且随输入水平峰值加速度的增大而明显增大,其机理是强地震动使液化范围加大;水平竖向两向地震动输入与单独水平地震动输入相比,前者场地液化范围增大,平均增大42%,侧移量增加,平均增加37%。 相似文献
19.
Ario Ceccotti Carmen Sandhaas Minoru Okabe Motoi Yasumura Chikahiro Minowa Naohito Kawai 《地震工程与结构动力学》2013,42(13):2003-2021
Multi‐storey buildings made of cross‐laminated timber panels (X‐lam) are becoming a stronger and economically valid alternative in Europe compared with traditional masonry or concrete buildings. During the design process of these multi‐storey buildings, also their earthquake behaviour has to be addressed, especially in seismic‐prone areas such as Italy. However, limited knowledge on the seismic performance is available for this innovative massive timber product. On the basis of extensive testing series comprising monotonic and reversed cyclic tests on X‐lam panels, a pseudodynamic test on a one‐storey X‐lam specimen and 1D shaking table tests on a full‐scale three‐storey specimen, a full‐scale seven‐storey building was designed according to the European seismic standard Eurocode 8 and subjected to earthquake loading on a 3D shaking table. The building was designed with a preliminary action reduction factor of three that had been derived from the experimental results on the three‐storey building. The outcomes of this comprehensive research project called ‘SOFIE – Sistema Costruttivo Fiemme’ proved the suitability of multi‐storey X‐lam structures for earthquake‐prone regions. The buildings demonstrated self‐centring capabilities and high stiffness combined with sufficient ductility to avoid brittle failures. The tests provided useful information for the seismic design with force‐based methods as defined in Eurocode 8, that is, a preliminary experimentally based action reduction factor of three was confirmed. Valid, ductile joint assemblies were developed, and their importance for the energy dissipation in buildings with rigid X‐lam panels became evident. The seven‐storey building showed relatively high accelerations in the upper storeys, which could lead to secondary damage and which have to be addressed in future research. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
20.
海南农村民居以砌体结构为主,具有门窗开口大、层高较高和整体性强等特点.为了研究分析这类民居的抗震性能与抗震对策,在收集大量当地农村民居样本的基础上,综合出典型结构模型,并对该典型模型及基于该模型的隔震模型和加强结构模型分别进行了模拟地震振动台试验.试验结果表明:隔震技术能明显降低结构地震反应,在高烈度地区应适当推广和运用.原结构模型基本满足7.5度设防标准.在8度大震作用下,结构遭遇严重破坏但未倒塌,说明其具有一定的抗倒塌能力.结构加固后,整体抗震性能得到了加强.结合试验结果,给出了相应对策与建议. 相似文献