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1.
The achievement of adequate performance objectives for buildings under increasing seismic intensities is not only related to the performance of structural members but also to the behavior of nonstructural elements. The need to properly design nonstructural elements for earthquakes has been largely demonstrated in the last few years and has become an important objective within the earthquake engineering community. A crucial aspect in the proper design of nonstructural elements is the definition of the seismic demand in terms of both absolute acceleration and relative displacement floor response spectra. In the first part of this study, relative displacement and absolute acceleration floor response spectra were computed for four reinforced concrete moment-resisting archetype frames via dynamic time-history analyses and were compared with floor response spectra predicted by means of two recent simplified methodologies available in the literature. It was observed that one of the existing methodologies is generally unable to predict consistent absolute acceleration and relative displacement floor response spectra. An improved procedure is developed for estimating consistent floor response spectra for building structures subjected to low and medium-high seismic intensities. This new procedure improves the predictions of a relative displacement floor response spectrum by constraining its ordinates at long nonstructural periods to the expected peak absolute displacement of the floor. The resulting acceleration and relative displacement response spectra are then consistently related by the well-known pseudo-spectral relationship over the entire nonstructural period range. The effectiveness of the proposed methodology was appraised against floor response spectra computed from nonlinear time-history analyses. 相似文献
2.
Seismic demand on light acceleration‐sensitive nonstructural components in European reinforced concrete buildings 
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下载免费PDF全文 In this paper, a parametric study is conducted in order to evaluate the seismic demand on light acceleration‐sensitive nonstructural components caused by frequent earthquakes. The study is motivated by the inconsistent approach of current building codes to the design of nonstructural components; the extensive nonstructural damage recorded after recent low‐intensity earthquakes also encouraged such a study. A set of reinforced concrete frame structures with different number of stories, that is, 1 to 10 stories, are selected and designed according to Eurocode 8. The structures are subjected to a set of frequent earthquakes, that is, 63% probability of exceedance in 50 years. Dynamic nonlinear analyses are performed on the reference structures in order to assess the accuracy of the equations to predict seismic forces acting on nonstructural components and systems in Eurocode. It is concluded that the Eurocode equations underestimate the acceleration demand on nonstructural components for a wide range of periods, especially in the vicinity of the higher mode periods of vibration of the reference structures; for periods sufficiently larger than the fundamental period of the structure, instead, the Eurocode formulation gives a good approximation of the floor spectra. Finally, a novel formulation is proposed for an easy implementation in future building codes based on the actual Eurocode provisions. The proposed formulation gives a good estimation of the floor spectral accelerations and is able to envelope the floor spectral peaks owing to the higher modes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
The seismic demand parameters including the floor acceleration amplification (FAA) factors and the interstory drift ratios (IDRs) were acquired from the floor response in time history analysis of a tall building subjected to selected ground motions. The FAA factors determined in this way are larger than those given in most current code provisions, but the obtained IDRs are close to the values given in some code provisions. Imposing a series of in‐plane pre‐deformations to two glass curtain wall (CW) specimens mounted on a shaking table, the IDRs were reproduced and the FAA factors were satisfied through applications of computed floor spectra compatible motion time histories, whose peak accelerations corresponded to the FAA factors. The CW specimens performed well during the whole experimental program with almost no change in the fundamental frequencies. No visible damage was observed in the glass panels. The maximum stresses detected in each component of the CW system were smaller than the design strengths. The obtained component acceleration amplification factor approached 3.35, which is larger than the value given in the current code provisions. In conclusion, the performance of the studied CW system is seismically safe. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
A statistical analysis of the peak acceleration demands for nonstructural components (NSCs) supported on a variety of stiff and flexible inelastic regular moment‐resisting frame structures with periods from 0.3 to 3.0 s exposed to 40 far‐field ground motions is presented. Peak component acceleration (PCA) demands were quantified based on the floor response spectrum (FRS) method without considering dynamic interaction effects. This study evaluated the main factors that influence the amplification or decrease of FRS values caused by inelasticity in the primary structure in three distinct spectral regions namely long‐period, fundamental‐period, and short‐period region. The amplification or decrease of peak elastic acceleration demands depends on the location of the NSC in the supporting structure, periods of the component and building, damping ratio of the component, and level of inelasticity of the supporting structure. While FRS values at the initial modal periods of the supporting structure are reduced due to inelastic action in the primary structure, the region between the modal periods experiences an increase in PCA demands. A parameter denoted as acceleration response modification factor (Racc) was proposed to quantify this reduction/increase in PCA demands. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
5.
Second‐mode tuned mass dampers in base‐isolated structures for reduction of floor acceleration 下载免费PDF全文
下载免费PDF全文 To reduce floor acceleration of base‐isolated structures under earthquakes, a tuned mass damper (TMD) system installed on the roof is studied. The optimal tuning parameters of the TMD are analyzed for linear base isolation under a generalized ground motion, and the performance of the TMD is validated using a suite of recorded ground motions. The simulation shows that a TMD tuned to the second mode of a base‐isolated structure reduces roof acceleration more effectively than a TMD tuned to the first mode. The reduction ratio, defined as the maximum roof acceleration with the TMD relative to that without the TMD, is approximately 0.9 with the second‐mode TMD. The higher effectiveness of the second‐mode TMD relative to the first‐mode TMD is attributed primarily to the unique characteristics of base isolation, ie, the relatively long first‐mode period and high base damping. The modal acceleration of the second mode is close to or even higher than that of the first mode in base‐isolated structures. The larger TMD mass ratio and lower modal damping ratio of the second‐mode TMD compared to the first‐mode TMD increases its effect on modal acceleration reduction. The reduction ratio with the second‐mode TMD improves to 0.8 for bilinear base isolation. Because of the detuning effect caused by the change in the first‐mode period in bilinear isolation, the first‐mode TMD is ineffective in reducing roof acceleration. Additionally, the displacement experienced by the second‐mode TMD is considerably smaller than that of the first‐mode TMD, thereby reducing the installation space for the TMD. 相似文献
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The dynamic response of equipment mounted on an isolated raised floor inside a building while the primary fixed base structure is subjected to harmonic and earthquake ground motions is numerically investigated. Sliding concave foundation (SCF) system is utilized for isolating the raised floor. The equations of motion for a MDOF shear building containing a SCF isolated raised floor with a mounted equipment are developed and the rigid link method is utilized to handle the non‐linearity of the system. The equipment, which can be modelled as a SDOF or MDOF system, may represent a critical computer unit or telecommunication processing system. SCF can be used easily to achieve the desired long period, necessary for protecting sensitive equipment. In this investigation, the ability of SCF in reducing the acceleration level experienced by the equipment inside a building is demonstrated while the lateral displacement is still within an acceptable range. The analysis considered the case of equipment housed in the upper floors of a building where the acceleration is amplified and the motion contains strong components at long periods. For this purpose, different excitations including both harmonic and real earthquake ground motions are employed and the performance of the system is evaluated. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
7.
The Vrancea subcrustal earthquakes of August 30,1986 and May 30,1990 are the two most recent seismic events that have occurred in Romania with moment magnitudes M W ≥ 6.9.The spectral analysis of the strong ground motions recorded in Bucharest reveals that despite small differences in magnitude between the 1986 and 1990 earthquakes,their frequency contents are very different,sometimes even opposing.The main focus of this study is to conduct a comparative analysis of the response spectra in terms of the bi-normalized response spectra(BNRS) proposed by Xu and Xie(2004 and 2007) for strong ground motions recorded in Bucharest during these two seismic events.The mean absolute acceleration and relative velocity response spectra for the two earthquakes are discussed and compared.Furthermore,the mean bi-normalized absolute acceleration and normalized relative velocity response spectra with respect to the control period T C are computed for the ground motions recorded in Bucharest in 1986 and 1990.The predominant period T P is also used in this study for the normalization of the spectral period axis.Subsequently,the methodology proposed by Martinez-Perreira and Bommer(1998) is applied in order to estimate the seismic intensity of the two events.The results are discussed and several conclusions regarding the possibility of using the bi-normalized response spectra(BNRS) are given. 相似文献
8.
This study uses instrumented buildings and models of code‐based designed buildings to validate the results of previous studies that highlighted the need to revise the ASCE 7 Fp equation for designing nonstructural components (NSCs) through utilizing oversimplified linear and nonlinear models. The evaluation of floor response spectra of a large number of instrumented buildings illustrates that, unlike the ASCE 7 approach, the in‐structure and the component amplification factors are a function of the ratio of NSC period to the supporting building modal periods, the ground motion intensity, and the NSC location. It is also shown that the recorded ground motions at the base of instrumented buildings in most cases are significantly lower than design earthquake (DE) ground motions. Because ASCE 7 is meant to provide demands at a DE level, for a more reliable evaluation of the Fp equation, 2 representative archetype buildings are designed based on the ASCE 7‐16 seismic provisions and exposed to various ground motion intensity levels (including those consistent with the ones experienced by instrumented buildings and the DE). Simulation results of the archetype buildings, consistent with previous numerical studies, illustrate the tendency of the ASCE 7 in‐structure amplification factor, [1 + 2(z/h)] , to significantly overestimate demands at all floor levels and the ASCE 7 limit of to in many cases underestimate the calculated NSC amplification factors. Furthermore, the product of these 2 amplification factors (that represents the normalized peak NSC acceleration) in some cases exceeds the ASCE 7 equation by a factor up to 1.50. 相似文献
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Ground motion prediction equations based on shallow crustal earthquakes in Georgia and the surrounding Caucasus 下载免费PDF全文
下载免费PDF全文 Jorjiashvili Nato Shengelia Ia Godoladze Tea Gunia Irakli Akubardia Dimitri 《地震科学（英文版）》2022,35(6):497-509
Strong ground motions caused by earthquakes with magnitudes ranging from 3.5 to 6.9 and hypocentral distances of up to 300 km were recorded by local broadband stations and three-component accelerograms within Georgia’s enhanced digital seismic network. Such data mixing is particularly effective in areas where strong ground motion data are lacking. The data were used to produce models based on ground-motion prediction equations (GMPEs), one benefit of which is that they take into consideration information from waveforms across a wide range of frequencies. In this study, models were developed to predict ground motions for peak ground acceleration and 5%-damped pseudo-absolute-acceleration spectra for periods between 0.01 and 10 s. Short-period ground motions decayed faster than long-period motions, though decay was still in the order of approximately 1/r. Faulting mechanisms and local soil conditions greatly influence GMPEs. The spectral acceleration (SA) of thrust faults was higher than that for either strike-slip or normal faults but the influence of strike-slip faulting on SA was slightly greater than that for normal faults. Soft soils also caused significantly more amplification than rocky sites. 相似文献
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竖向地震动加速度反应谱特性 总被引：3，自引：0，他引：3
以33次地震中的地表地震动记录为数据基础,考虑场地条件、震级和距离的影响,分别对竖向地震动的加速度规准化反应谱和双规准化反应谱进行了研究。结果表明,规准反应谱明显受到场地条件、震级和震中距的影响,不同场地、距离和震级的平均规准反应谱之间差别显著;相比较而言,不依赖于场地、距离和震级的平均双规准反应谱之间却表现出良好的规律性和一致性。双规准反应谱的统一特性可以为竖向地震动设计谱的预测提供参考依据。 相似文献
11.
现阶段基于性能的抗震设计思想不仅关注结构自身体系的安全,而且保护非结构构件在地震作用下使用功能完好。对于工业建筑结构,生产设备在地震作用下受损会影响震后功能恢复。加速度敏感型非结构构件一般采用楼层加速度指标来量化其地震损伤程度。以三个不同高度的钢抗弯框架规则结构体系为研究对象,采用与竖向目标谱匹配的近断层非脉冲和脉冲地震动作为竖向地震输入,考察不同质量不规则程度下,楼层竖向绝对加速度随建筑高度的变化趋势,并从反应谱角度分析不规则质量分布对楼层加速度响应的影响。结果表明:4层结构在非脉冲地震作用下楼层顶层处竖向绝对加速度是地面竖向峰值加速度的5倍之多,某一层质量的突变会引起该层及其他楼层竖向绝对加速度的明显变化。另外,对现有计算楼层竖向加速度响应的经验公式进行验证,发现美国ASCE 7-16规范的估计结果偏于保守。 相似文献
12.
俯冲带地区竖向地震动的阻尼修正系数在工程结构抗震设计中起着重要作用。由于俯冲带地区的板块构造复杂,俯冲带地区的地震可划分为浅壳上地幔地震、板内地震和板间地震3种类型。为研究不同类型俯冲带地震的竖向地震动阻尼修正系数间是否具有显著差异而需要分别建立不同的阻尼修正系数模型,采用日本俯冲带地区的地震动数据,通过假设检验和构造差异指标的方式对不同类型地震的竖向加速度和位移反应谱的阻尼修正系数进行两两比较。结果显示:不同地震类型的竖向地震动阻尼修正系数在众多谱周期上存在统计意义和工程实际意义上的显著差异。该研究表明:研究俯冲带地区竖向地震动阻尼修正系数时需要考虑地震类型的影响。 相似文献
13.
选择美国加州大学圣地亚哥分校7层钢筋混凝土剪力墙足尺结构振动台实验,开展结构损伤识别研究,实验采用白噪声、环境振动和不同强度的地震动交替激发,记录地震动激发实验前后的结构反应。基于该记录计算和对比自振频率和振型曲率的变化、剪切波走时及其变化和结构层间位移角,分析发现一层和二层振型曲率较大,走时较长,走时变化也较大,现场检查发现一层和二层的破坏也较为严重,这些参数可用于识别结构损伤程度和定位损伤位置,而自振频率和层间位移角变化仅可反映出结构损伤程度,难以揭示结构损伤位置。 相似文献
14.
G. Alguacil F. Vidal M. Navarro A. García-Jerez J. Pérez-Muelas 《Bulletin of Earthquake Engineering》2014,12(5):1889-1908
Exceptional ground motions have been observed in the near-source region in relatively small and moderate earthquakes such as the Lorca earthquake of 2011. In the Mw 5.2 mainshock, horizontal peak ground acceleration reached 0.37 g at the LOR accelerograph station in the north-central part of the town. Maximum ground acceleration and velocity in this station was strongly polarised in the fault’s strike-normal axis, a feature interpreted as a near-field effect of rupture directivity. This quake hit the Lorca area causing serious structural damage, unevenly distributed in the urban area as result of a heterogeneous spread of building vulnerability and seismic shaking severity. This study investigates the characteristics of the earthquake shaking at the LOR station (on rock) and other 11 zones of Lorca with different site conditions. We have computed the 1-D transfer functions of the shallow structure at these 11 points with available local Vs models obtained with SPAC technique. These transfer functions were used to convolve the LOR accelerogram and simulate the ground motion which occurred at each site. A set of key engineering ground-motion parameters obtained here, indicate different shake levels at each site and all these values are clearly above the LOR station ones. These parameter values are in the range of typical expected values for European earthquakes with local intensity VIII. Their large values, especially those of acceleration response spectra and energy input spectra, more clearly for periods between 0.4 and 0.6 s, point out that the seismic demand has been quite high and help to explain the heavy damage spread on the town’s buildings. 相似文献
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本文旨在分析脉冲型地震动中不同频率的地震动分量对于原始地震动幅值及其非弹性反应谱的影响.首先以近期12次大地震的53条典型脉冲型地震动为数据基础,基于多尺度分解方法获取脉冲型地震动中的高频分量和低频分量.为与传统方法对比,本文获取了能够表征地震动脉冲特性的卓越分量及滤除卓越分量的剩余分量.然后对比分析原始地震动和4种地震动分量的幅值特征和非弹性反应谱的特性,以讨论地震动分量对原始地震动幅值参数及其非弹性反应谱的影响.最后结合简谐地震动模型和地震动分量的性质,讨论脉冲型地震动非弹性反应谱诸多特征的产生原因.分析发现,低频分量不仅是控制脉冲型地震动速度和位移幅值的主要因素,其对原始地震动的加速度幅值也具有不可忽略的影响.低频分量也是导致脉冲型地震动非弹性位移比谱偏大以及强度折减系数谱偏小的直接原因,从而造成结构在脉冲型地震动作用下需要具有更大的非弹性位移以及更高的强度需求. 相似文献
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Newmark design spectra have been implemented in many building codes, especially in building codes for critical structures. Previous studies show that Newmark design spectra exhibit lower amplitudes at high frequencies and larger amplitudes at low frequencies in comparison with spectra developed by statistical methods. To resolve this problem, this study considers three suites of ground motions recorded at three types of sites. Using these ground motions, influences of the shear-wave velocity, earthquake magnitudes, source-to-site distances on the ratios of ground motion parameters are studied, and spectrum amplification factors are statistically calculated. Spectral bounds for combinations of three site categories and two cases of earthquake magnitudes are estimated. Site design spectrum coefficients for the three site categories considering earthquake magnitudes are established. The problems of Newmark design spectra could be resolved by using the site design spectrum coefficients to modify the spectral values of Newmark design spectra in the acceleration sensitive, velocity sensitive, and displacement sensitive regions. 相似文献
17.
Validation of the SCEC Broadband Platform simulations for tall building risk assessments considering spectral shape and duration of the ground motion 下载免费PDF全文
下载免费PDF全文 Earthquake simulation technologies are advancing to the stage of enabling realistic simulations of past earthquakes as well as characterizations of more extreme events, thus holding promise of yielding novel insights and data for earthquake engineering. With the goal of developing confidence in the engineering applications of simulated ground motions, this paper focuses on validation of simulations for response history analysis through comparative assessments of building performance obtained using sets of recorded and simulated motions. Simulated ground motions of past earthquakes, obtained through a larger validation study of the Southern California Earthquake Center Broadband Platform, are used for the case study. Two tall buildings, a 20‐story concrete frame and a 42‐story concrete core wall building, are analyzed under comparable sets of simulated and recorded motions at increasing levels of ground motion intensity, up to structural collapse, to check for statistically significant differences between the responses to simulated and recorded motions. Spectral shape and significant duration are explicitly considered when selecting ground motions. Considered demands include story drift ratios, floor accelerations, and collapse response. These comparisons not only yield similar results in most cases but also reveal instances where certain simulated ground motions can result in biased responses. The source of bias is traced to differences in correlations of spectral values in some of the stochastic ground motion simulations. When the differences in correlations are removed, simulated and recorded motions yield comparable results. This study highlights the utility of physics‐based simulations, and particularly the Southern California Earthquake Center Broadband Platform as a useful tool for engineering applications. 相似文献
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设计反应谱长周期区段的研究 总被引：24，自引：7，他引：17
本文利用近20年国内外大地震时获得的数字强震仪记录分析强震动的长周期分量特性,给出了不同场地上的平均加速度反应谱及其拟合曲线。结果表明,现行抗震设计规范中设计谱的特征周期和长周期谱值明显偏小。在此基础上提出了长周期设计反应谱的修正建议。文中还根据统计分析提出了不同阻尼比的反应谱修正公式。 相似文献
20.
To evaluate and measure the effectiveness of active control schemes in reducing the response of structures subjected to earthquake excitations, it is common to use recorded or artificially generated earthquakes as input motions. This paper introduces the response spectrum analysis to evaluate linear control systems for seismic inputs defined by code‐prescribed or site‐specific ground response spectra. Using such a method one can evaluate a control system in a single analysis for the ensemble of time histories that are represented by the input response spectra. The response spectrum analysis can also facilitate the implementation of comprehensive parametric studies. A generalized response spectrum method is used to analyse systems with non‐symmetrical matrices that are caused by the general nature of the control actions imposed on the structure. The application of the method is demonstrated on several numerical examples of a building structure where the control force is applied through an active tuned‐mass damper. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献