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1.
An orthogonal set of principal axes is defined for earthquake ground motions. These principal axes are obtained such that the corresponding variances of motion have maximum, minimum and intermediate values and the covariances equal zero. This indicates that the corresponding components of motion along the principal axes are uncorrelated with respect to each other. Since real earthquake accelerograms are assumed to be reasonably well represented by Gaussian random processes, the three components of motion along the principal axes are statistically independent of each other. Using these principal axes and applying the moving-window technique to the ground accelerograms recorded during the San Fernando earthquake of 9 February 1971, time-dependent characteristics of three-dimensional ground motions along principal axes are determined. Results of the analysis indicate significant correlation between directions of principal axes and directions from the recording stations to the fault slip zone. It is concluded that three components of ground motion can be generated stochastically with statistical independence being maintained, provided they are assumed to be directed along principal axes. 相似文献
2.
Rotation-invariant measures of earthquake response spectra 总被引：1，自引：1，他引：0
A new procedure for combining the response spectra of two horizontal components of recorded ground motion is presented. The presented formulation accounts for different orientations of accelerometer sensors and derives the maximum and the expected (mean) horizontal response spectra at a site, both of which are invariant to rotation of sensor axes. The maximum response spectrum is derived as the peak resultant response of single degree of freedom oscillators subjected to the as-recorded ground acceleration. The expected spectrum is derived by projecting the displacement response (due to as-recorded motion) along two orthogonal axes to a principal axes in which the displacement responses are uncorrelated. This property is used to formulate an approximation for the expected response spectrum over all possible sensor orientations. A large set of accelerometric data from Europe and the Middle East is used to demonstrate the applicability of the proposed response spectral measures. 相似文献
3.
A method for generating an ensemble of orthogonal horizontal ground motion components with correlated parameters for specified earthquake and site characteristics is presented. The method employs a parameterized stochastic model that is based on a time‐modulated filtered white‐noise process with the filter having time‐varying characteristics. Whereas the input white‐noise excitation describes the stochastic nature of the ground motion, the forms of the modulating function and the filter and their parameters characterize the evolutionary intensity and nonstationary frequency content of the ground motion. The stochastic model is fitted to a database of recorded horizontal ground motion component pairs that are rotated into their principal axes, a set of orthogonal axes along which the components are statistically uncorrelated. Model parameters are identified for each ground motion component in the database. Using these data, predictive equations are developed for the model parameters in terms of earthquake and site characteristics and correlation coefficients between parameters of the two components are estimated. Given a design scenario specified in terms of earthquake and site characteristics, the results of this study allow one to generate realizations of correlated model parameters and use them along with simulated white‐noise processes to generate synthetic pairs of horizontal ground motion components along the principal axes. The proposed simulation method does not require any seed recorded ground motion and is ideal for use in performance‐based earthquake engineering. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
<正>Ground motion records are often used to develop ground motion prediction equations(GMPEs) for a randomly oriented horizontal component,and to assess the principal directions of ground motions based on the Arias intensity tensor or the orientation of the major response axis.The former is needed for seismic hazard assessment,whereas the latter can be important for assessing structural responses under multi-directional excitations.However,a comprehensive investigation of the pseudo-spectral acceleration(PSA) and of GMPEs conditioned on different axes is currently lacking.This study investigates the principal directions of strong ground motions and their relation to the orientation of the major response axis, statistics of the PSA along the principal directions on the horizontal plane,and correlation of the PSA along the principal directions on the horizontal plane.For these,three sets of strong ground motion records,including intraplate California earthquakes,inslab Mexican earthquakes,and interface Mexican earthquakes,are used.The results indicate that one of the principal directions could be considered as quasi-vertical.By focusing on seismic excitations on the horizontal plane,the statistics of the angles between the major response axis and the major principal axis are obtained;GMPEs along the principal axes are provided and compared with those obtained for a randomly oriented horizontal component;and statistical analysis of residuals associated with GMPEs along the principal directions is carried out. 相似文献
5.
Power spectral density which describes frequency content is considered one of the most significant properties to be taken into account when generating ground motions through the use of stochastic processes. Using a smoothed and normalized Fourier amplitude spectrum, frequency content for components of motion along a set of principal axes is estimated. Fourier amplitude spectra obtained by this moving-window technique are presented which show the time dependency of frequency content for motions produced by the San Fernando earthquake of 9 February 1971. A mathematical model to simulate ground motion processes is proposed for which both the intensity and frequency content are non-stationary. Using this mathematical model with parameter characteristics along principal axes similar to those of the motions recorded during the San Fernando earthquake, three-dimensional ground motions are synthetically generated. The properties of the simulated motions show general characteristics similar to the characteristics observed in real accelerograms. The suggested model is considered adequate for engineering purposes. 相似文献
6.
双向地震动作用的拟等延性系数谱 总被引：1，自引：0，他引：1
首先建立了以强度折减系数表述的恢复力特性满足二维屈服面模型的理想弹塑性单质点系统(它在2个相互垂直的主轴方向上分别具有水平平动自由度)在双向地震动作用下的归一化运动方程。然后引入单向地震动作用下等延性系数的强度折减系数谱,给出了双向地震动作用的拟等延性系数谱(定义为系统分别承受双向和单向地震动作用,在同一主轴方向上的最大位移反应之比)最后通过硬土场地10组双向地震动记录拟等延性系数谱的统计平均结果,分析了结构周期、位移延性系数和阻尼等因素对谱值及结构双向地震反应的影响。结果表明,双向地震动作用与单向地震动作用相比主要增加结构较长周期方向的最大位移反应。若在基于位移的抗震设计中降低结构较短周期方向的设计位移延性系数,可在一定程度上降低双向地震动的不利影响。因定义的谱为比值形式,阻尼对其影响不大。 相似文献
7.
The results of long-term (2001–2009) measurements of fractures in sedimentary rocks of the Badenian and Pannonian age within
the Rust-Fertorakos Highland and adjacent areas are presented and interpreted in terms of paleostresses in the study. The
Rust-Fertorakos Highland has a nearly north-south trending strike and separates the Vienna and Pannonian Basins. It is expressed
not only in the topography but also in the thickness of the sedimentary cover. Faults in the basement of the Rust-Fertorakos
Highland have a nearly north-south strike diagonal to the general NE-SW strike of the faults of the basement of the Vienna
Basin. The data of measurements of joints made in quarries and on road slopes that were subsequently computer processed using
two independent techniques indicate that, along with joint systems, which are orthogonal to the rock bedding and are of a
primary lithogenetic origin, joints joining to form systems obliquely oriented to the bedding are quite common in the region.
These secondary joint systems have been formed at later stages of development of already lithified rocks under the influence
of tectonic paleostresses. Interpreting pairs of secondary systems as conjugated shear joints, the authors have reconstructed
the orientations of the axes of the relevant tectonic paleostresses. At some observation points, the identification of conjugated
shear systems has been ambiguous. In these cases, two possible solutions for the paleostress axes have been drawn. Despite
some ambiguities, all of the solutions obtained have a steady tendency in terms of the orientation of the minimum compression
axis T
3. This axis is subhorizontal and is oriented nearly east-west with some variation. The maximum compression axis T
1 and the intermediate principal stress axis T
2 are normally inclined to the horizontal, and the orientation of these axes depends on the observation point. 相似文献
8.
求解鹤岗强矿震震源机制解结果,表现出走滑伴随逆断层和正断层活动、非双力偶型的多样性。两组节面优势分布方向和节面的倾角优势分布不显著,两者分布无明显规律,反映出矿井下破裂面比较复杂。矿震震源主压应力释放优势方向北西310°左右,优势倾角为25°～60°;主张应力轴走向NE,主张应力场优势方向为北东60°左右,仰角在30～70°之间;中等应力轴(N)近于垂直,优势倾角为70～90°。矿震震源机制解显示的矿区最大主应力方向与区域构造应力场的最大主应力方向近似正交,矿震震源机制主应力轴优势倾角远大于区域构造地震,反映的是矿区采煤生产的次生构造应力环境重力应力场的贡献明显。 相似文献
9.
Damage response of multistorey r/c buildings with different structural systems subjected to seismic motion of arbitrary orientation 
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下载免费PDF全文 In the present study the combined influence of seismic orientation and a number of parameters characterizing the structural system of Reinforced Concrete (R/C) buildings on the level of expected damages are examined. For the purposes of the above investigation eight medium‐rise buildings are designed on the basis of the current seismic codes. The structural characteristics examined are the ratio of the base shear received by the structural walls, the ratio of horizontal stiffness in two orthogonal directions and the structural eccentricity. Then, the buildings are analyzed by nonlinear time response analysis using 100 bidirectional earthquake ground motions. The two horizontal accelerograms of each ground motion are applied along horizontal orthogonal axes, forming 72 different angles with the structural axes. The structural damage is expressed in terms of the Park and Ang damage index. The results of the analyses revealed that the damage level of the buildings is strongly affected by the incident angle of the ground motion. The extent at which the orientation of the seismic records influences the damage response depends on the structural system and the distance of the record to the fault rupture. As a consequence, the common practice of applying the earthquake records along the structural axes can lead to significant underestimation of structural damage. Also, it was shown that the structural eccentricity can significantly differentiate the seismic damage level, as well as the impact of the earthquake orientation on the structural damage. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
This paper aims to develop an improved understanding of the critical response of structures to multicomponent seismic motion characterized by three uncorrelated components that are defined along its principal axes: two horizontal and the vertical component. An explicit formula, convenient for code applications, has been derived to calculate the critical value of structural response to the two principal horizontal components acting along any incident angle with respect to the structural axes, and the vertical component of ground motion. The critical response is defined as the largest value of response for all possible incident angles. The ratio rcr/rsrss between the critical value of response and the SRSS response—corresponding to the principal components of ground acceleration applied along the structure axes—is shown to depend on three dimensionless parameters: the spectrum intensity ratio γ between the two principal components of horizontal ground motion characterized by design spectra A(Tn) and γA(Tn); the correlation coefficient α of responses rx and ry due to design spectrum A(Tn) applied in the x‐ and y‐directions, respectively; and β = ry/rx. It is demonstrated that the ratio rcr/rsrss is bounded by 1 and . Thus the largest value of the ratio is , 1.26, 1.13 and 1.08 for γ = 0, 0.5, 0.75 and 0.85, respectively. This implies that the critical response never exceeds times the result of the SRSS analysis, and this ratio is about 1.13 for typical values of γ, say 0.75. The correlation coefficient α depends on the structural properties but is always bounded between −1 and 1. For a fixed value of γ, the ratio rcr/rsrss is largest if β = 1 and α = ±1. The parametric variations presented for one‐storey buildings indicate that this condition can be satisfied by axial forces in columns of symmetric‐plan buildings or can be approximated by lateral displacements in resisting elements of unsymmetrical‐plan buildings. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
11.
K. G. Kostinakis A. M. Athanatopoulou I. E. Avramidis 《Bulletin of Earthquake Engineering》2013,11(2):637-661
The aim of the present paper is to evaluate by means of nonlinear dynamic analysis four different procedures for the selection of sectional forces needed for the design of R/C frames. For this purpose, a single-story building is designed using four different procedures to select the sets of internal forces needed for the calculation of longitudinal reinforcement. All the four procedures are based on the results of linear response history analysis. Nonlinear dynamic analyses under 16 bi-directional ground motions are performed for 4 different seismic intensity levels. The two horizontal accelerograms of each ground motion are applied along horizontal orthogonal axes forming with the structural axes several incident angles. The results of this study demonstrate that one of the investigated procedures that takes into account the critical seismic angle is more efficient for the design of R/C frame elements. 相似文献
12.
Yeudy Felipe Vargas-Alzate Vitor Silva Dimitrios Vamvatsikos Lluis Gonzaga Pujades 《地震工程与结构动力学》2022,51(1):191-212
A simplified procedure is developed to consider the azimuthal orientation of buildings when estimating seismic risk. Two square-plan reinforced concrete building models are considered as a testbed, one with similar and one with dissimilar properties along the two principal horizontal axes. The fragility of both structures is analysed using a set of ground motion records rotated to multiple incidence angles to develop orientation-dependent fragility functions. It has been observed that, re-orienting all records so that these structures have the same azimuth vis-à-vis the corresponding epicentre leads to significant differences compared to assuming random orientations. Additional results stemming from single-degree-of-freedom oscillators further confirm such findings, showing a dependence to the proximity to the faults and the level of dissimilarity in the principal horizontal axes of the structure. The end results point to a non-negligible bias in assessment studies when a structure's orientation with respect to governing rupture scenarios is not taken into account. It is shown that the median of fragility curves calculated for un-rotated incidence angles can be bias-corrected through shifted by an amount that depends on the azimuthal orientation and level of axes-dissimilarity of structures. 相似文献
13.
On the basis of the GPS data obtained from repeated measurements carried out in 2004 and 2007,the horizontal principal strain of the Chinese mainland is calculated,which shows that the direction of principal compressive strain axis of each subplate is basically consistent with the P-axis of focal mechanism solution and the principal compressive stress axis acquired by geological method.It indicates that the crustal tectonic stress field is relatively stable in regions in a long time.The principal compressive stress axes of Qinghai-Tibet and Xinjiang subplates in the western part of Chinese mainland direct to NS and NNE-SSW,which are controlled by the force from the col-lision of the Eurasia Plate and India Plate.The principal compressive strain axes of Heilongjiang and North China subplates in the eastern part direct to ENE-WSW,which shows that they are subject to the force from the collision and underthrust of the Eurasia Plate to the North America and Pacific plates.At the same time,they are also af-fected by the lateral force from Qinghai-Tibet and Xinjiang subplates.The principal compressive strain axis of South China plate is WNW-ESE,which reflects that it is affected by the force from the collision of Philippine Sea Plate and Eurasia Plate and it is also subject to the lateral force from Qinghai-Tibet subplate.It is apparent from the comparison between the principal compressive strain axes in the periods of 2004～2007 and 2001～2004 that the acting directions of principal compressive stress of subplates in both periods are basically consistent.However,there is certain difference between their directional concentrations of principal compressive stress axes.The sur-face strain rates of different tectonic units in both periods indicate that the events predominating by compressive variation decrease,while the events predominating by tensile change increase. 相似文献
14.
将每个震源机制解的两个节面交替取作尝试的断层面,使计算的断层面上的剪切力方向与观测的断层面的滑动方向夹角最小,从而根据29个震源机制解结果反演了唐山余震区三个分区的平均主应力方向和中等主应力相对大小。本文结果说明,唐山余震区的最大主应力轴水平,取近东西方向,较之1976年唐山大震前的方向可能水平地顺时针转动了大约30。对同样地区用平均P,B,T轴推断主应力方向的结果与用上述方法所得结果基本一致。所作的数值试验说明,在特定情况下,用平均P,B,T轴推断构造应力主轴方向时有可能出现系统偏差。 相似文献
15.
16.
Modern tectonic stress field in the Chinese mainland inverted from focal mechanism solutions 总被引：1，自引：0，他引：1
IntroductionTheinversionapproachofregionalstressfielddevelopedinrecent10to20yearsprovidesausefultoolforstudyingthemeanstressinagivenregion(Angeller,1979;Ellsworth,1981,Xu,Ge,1984).Becauseitusesmultitudinousfaultsinsteadofsinglefault,itcanremovetheinhomogeneityoflocalmediumsoastorevealtheregionalstressinformation.Besides,thismethodproducesaRvalue,whichisdefinedby(O-2--q)/(q--q),andmaydescribestherelativemagnitUdeofintermediateprincipalstress,whereq,acand%arethemaximum,theintermediateandthemi… 相似文献
17.
The responses, re, given by several multicomponent combination rules used in seismic codes for determining peak responses to three ground motion components are evaluated for elastic systems and compared with the critical response rcr; this is defined as the largest response for all possible incident angles of the seismic components and obtained by means of the CQC3‐rule when a principal seismic component is vertical, or the GCQC3‐rule when it departs from the vertical direction. The combination rules examined are the SRSS‐, 30%‐, 40%‐ and IBC‐rules, considering different alternatives for the design horizontal spectrum. Assuming that a principal seismic component is along the vertical direction, the upper and lower bounds of the ratio re/rcr for each combination rule are determined as a function of the spectral intensity ratio of the horizontal seismic components and of the responses to one seismic component acting alternately along each structural axis. Underestimations and overestimations of the critical response are identified for each combination rule and each design spectrum. When a component departs from the vertical direction, the envelopes of the bounds of the ratio re/rcr for each combination rule are calculated, considering all possible values of the spectral intensity ratios. It is shown that the inclination of a principal component with respect to the vertical axis can significantly reduce the values of re/rcr with respect to the case when the component is vertical. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
18.
Jaime Urrutia-Fucugauchi Margarita Delgadillo-Peralta Ligia Pérez-Cruz Miriam Velasco-Villarreal 《Studia Geophysica et Geodaetica》2012,56(3):769-787
Initial results of a thermal treatment study on the anisotropy of magnetic susceptibility (AMS) of impact breccias from Chicxulub crater are used to investigate the nature of the magnetic fabrics. Chicxulub impact breccias are heterogeneous materials, with carbonate, basement and melt clasts within carbonate-rich or melt-rich matrix. Samples studied come from the carbonate-rich basal unit Lower Suevite in the Yaxcopoil-1 borehole impactite sequence (core depth interval: 885?C895 m). The Lower Suevite is characterized by mixed prolate and oblate ellipsoids with shallow to steep principal susceptibility axes, which had been related to emplacement as an excavation flow with ground-surge components during the early cratering stages. Thermal treatment results in changes in the fabrics with a tendency to oblate fabrics. Stepwise thermal treatment up to 700°C reveals different behaviors for the oblate, neutral and prolate fabrics marked by changes in AMS parameters and principal susceptibility axis orientations. A sample with oblate fabrics and vertical minimum axes showed an increase of magnetic susceptibility at high temperatures, indicating formation of secondary magnetite and fabric enhancement. A sample with neutral ellipsoid showed heating-induced changes towards oblate fabrics and vertical minimum susceptibility axes. Samples characterized by prolate ellipsoids with horizontal maximum axes showed no directional changes. In a sample with apparent intermediate or inverse fabrics, vertical maximum axes showed changes to horizontal inclinations, with the intermediate and maximum axes switching positions. Changes induced by stepwise thermal treatment appear useful to characterize the fabrics of impact lithologies. Further investigation of heating-induced effects in mineralogy, grain size and textural changes is, however, required to relate the different behaviors observed after stepwise thermal treatment with the magnetic mineralogy and emplacement mode of the breccias. 相似文献
19.
岩石的磁化率张量的统计处理，传统的处理方法是用费歇尔法，但对于火成岩等磁化率各向异性较弱的岩石，这种方法存在着局限性。本文介绍了“自益再采样法”，并与传统的方法进行了对比，指出，自益再采样法不仅有助于消除测量过程中的误差，而且它是建立在数据的实际分布之上的，能更准确地反映磁化率轴的实际分布方位以及方位的分散程度。； 相似文献
20.
The existence of the principal directions of the ground motion based on Arias intensity is well-known. These principal directions do not necessarily coincide with the orientations of recording sensors or with the orientations along which the ground motion parameters such as the peak ground acceleration and the pseudo-spectral acceleration (PSA) are maximum. This is evidenced by the fact that the maximum PSA at different natural vibration periods for horizontal excitations do not correspond to the same orientation. A recent analysis carried out for California earthquake records suggests that an orientation-dependent ground motion measurement for horizontal excitations can be developed. The main objective of this study is to investigate and provide seismic ground motion measurements in the horizontal plane, including bidirectional horizontal ground motions, for Mexican interplate and inslab earthquake records. Extensive statistical analyses of PSA are conducted for the assessment, The analysis results suggest that similar to the case of California records, the average behavior of the ratio of the PSA to the maximum resulting PSA can be approximated by a quarter of an ellipse in one quadrant; and that the ratio can be considered to be independent of the value of the maximum resulting PSA, earthquake magnitude, earthquake distance and the focal depth. Sets of response ratios and attenuation relationships that can be used to represent a bidirectional horizontal ground motion measurement for Mexican interplate and inslab earthquakes were also developed. 相似文献