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1.
Ground-Motion Prediction Equations (GMPEs) for inelastic displacement and ductility demands of constant-strength SDOF systems 总被引：1，自引：1，他引：0
The objective of this paper is to present ground-motion prediction equations for ductility demand and inelastic spectral displacement
of constant-strength perfectly elasto-plastic single-degree-of-freedom (SDOF) oscillators. Empirical equations have been developed
to compute the ductility demand as a function of two earthquake parameters; moment magnitude, and source-to-site distance;
one site parameter, the ground type; and three oscillator parameters, an undamped natural period, critical damping ratio,
and the mass-normalized yield strength. In addition, a comparative study of the proposed model with selected previous studies
and recommendations of Eurocode 8 is presented. Proposed equations can easily be incorporated in existing probabilistic seismic
hazard analysis (PSHA) software packages with the introduction of an additional parameter. This leads to hazard curves for
inelastic spectral displacement, which can provide better estimates of target displacement for nonlinear static procedures
and an efficient intensity measure for probabilistic seismic demand analysis (PSDA). Proposed equations will be useful in
performance evaluation of existing structures. 相似文献
2.
Bridges are crucial to the transportation network in a region struck by an earthquake. Collapse of a bridge determines if a road is passable. Ability of a bridge to carry traffic load after an earthquake determines the weight and speed of vehicles that can cross it. Extent of system and component structural damage in bridges determines the cost and time required for repair. Today, post‐earthquake bridge evaluation is qualitative rather than quantitative. The research presented in this paper aims to provide a quantitative engineering basis for quick and reliable evaluation of the ability of a typical highway overpass bridge to function after an earthquake. The Pacific Earthquake Engineering Research (PEER) Center's probabilistic performance‐based evaluation approach provides the framework for post‐earthquake bridge evaluation. An analytical study was performed that linked engineering demand parameters to earthquake intensity measures. The PEER structural performance database and reliability analysis tools were then used to link demand parameters to damage measures. Finally, decision variables were developed to describe three limit states, repair cost, traffic function, and collapse, in terms of induced damage. This paper presents the analytical models used to evaluate post‐earthquake bridge function, decision variables and their correlation to the considered limit states, and fragility curves that represent the probability of exceeding a bridge function limit state given an earthquake intensity. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
Maria Teresa Giugliano Alessandra Longo Rosario Montuori Vincenzo Piluso 《地震工程与结构动力学》2011,40(13):1455-1474
Structural engineering problems are always affected by many sources of uncertainty, such as aleatory of material properties, applied loads and earthquake intensity, therefore, seismic assessment of structures should be based on probabilistic methods. Since PBSD (Performance‐based Seismic Design) philosophy was formulated, many researches have been conducted in this field in order to develop simple and accurate procedures for evaluating structural reliability. An important contribution has been provided by Jalayer and Cornell, who have developed a closed‐form expression to evaluate the mean annual frequency of exceeding a defined limit state. In this paper, by assuming the record‐to‐record variability as the only source of uncertainty, the seismic reliability of concentrically braced frames designed according to traditional and innovative methodologies is investigated, and a comparison between their performances is presented. In particular, two design methodologies have been applied: Eurocode 8 provisions and a new design methodology based on a rigorous application of ‘capacity design’ criteria. The innovative reduced section solution strategy, based on the reduction of cross sections at bracing member ends, has also been analysed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
Probabilistic demand and fragility assessment of welded column splices in steel moment frames 
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下载免费PDF全文 An assessment of seismic demands and capacities of welded column splice (WCS) connections in steel moment frames is presented. For demand assessment, nonlinear dynamic analyses are conducted for two case‐study buildings, that is, a 4‐story and a 20‐story moment frame. Results from the nonlinear dynamic analyses are assessed through a probabilistic seismic demand analysis (PSDA) framework to characterize recurrence rates of longitudinal flange stress in these connections. The PSDA is applied in two contexts. First, in the context of WCS connections constructed prior to the M 6.7 1994 Northridge earthquake, the PSDA is combined with sophisticated finite element‐based fracture mechanics analysis to compute the mean annual frequencies of fracture in these connections. The pre‐Northridge WCS are especially critical because they feature partial joint penetration and brittle materials that compromise their resistance to fracture. The analysis indicates that the mean annual frequencies of fracture in these connections may be unacceptably high for both the 4‐story and the 20‐story frames. This warrants a serious and urgent consideration of retrofit strategies. These findings are attributed to the brittleness of the pre‐Northridge splices (as indicated by the fracture mechanics simulations), as well as the force‐controlled nature of these components, wherein low‐intensity ground motions contribute disproportionately to fracture risk, as evidenced by fracture risk disaggregation. Second, in the context of new construction, the PSDA provides meaningful stress magnitudes for design. Currently, WCS connections employ complete joint penetration welds with the intent to develop the smaller column flange in yielding. The PSDA conducted in this study suggests that this requirement may be too stringent because stress demands in the splices corresponding even to high return periods (e.g., 2475 years) are significantly lower (~40 ksi), as compared with the stress required to yield the column (~55 ksi). Limitations of the study are outlined. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
A Probabilistic Displacement-based Vulnerability Assessment Procedure for Earthquake Loss Estimation 总被引：8，自引：3，他引：5
Earthquake loss estimation studies require predictions to be made of the proportion of a building class falling within discrete damage bands from a specified earthquake demand. These predictions should be made using methods that incorporate both computational efficiency and accuracy such that studies on regional or national levels can be effectively carried out, even when the triggering of multiple earthquake scenarios, as opposed to the use of probabilistic hazard maps and uniform hazard spectra, is employed to realistically assess seismic demand and its consequences on the built environment. Earthquake actions should be represented by a parameter that shows good correlation to damage and that accounts for the relationship between the frequency content of the ground motion and the fundamental period of the building; hence recent proposals to use displacement response spectra. A rational method is proposed herein that defines the capacity of a building class by relating its deformation potential to its fundamental period of vibration at different limit states and comparing this with a displacement response spectrum. The uncertainty in the geometrical, material and limit state properties of a building class is considered and the first-order reliability method, FORM, is used to produce an approximate joint probability density function (JPDF) of displacement capacity and period. The JPDF of capacity may be used in conjunction with the lognormal cumulative distribution function of demand in the classical reliability formula to calculate the probability of failing a given limit state. Vulnerability curves may be produced which, although not directly used in the methodology, serve to illustrate the conceptual soundness of the method and make comparisons with other methods. 相似文献
6.
基于改进云图法的结构概率地震需求分析 总被引：2，自引：0，他引：2
概率地震需求分析是美国太平洋地震工程研究中心(Pacific Earthquake Engineering ResearchCenter,PEER)提出的新一代"性能化地震工程(Performance-Based Earthquake Engineering,PBEE)"理论框架的重要一环。传统的概率地震需求分析方法称为"云图法",这种方法针对确定性结构进行一系列地震动作用下的非线性动力分析,从而得到地震动强度参数与结构地震需求的"云图"。然而,传统的云图法只能考虑地震动的不确定性,而无法考虑结构的不确定性。为此,结合拉丁超立方体抽样技术,提出一种能综合考虑地震动不确定性和结构不确定性的改进云图法,并将传统的概率地震需求分析内容拓展为概率地震需求模型、概率地震需求易损性分析、概率地震需求危险性分析三个层次。以一榀五层三跨钢筋混凝土框架结构为例,分别采用传统云图法和改进云图法对其进行概率地震需求分析,得到了该结构的概率地震需求模型、地震需求易损性曲线和地震需求危险性曲线。分析结果表明:提出的方法可以有效地考虑地震动与结构的不确定性,避免不考虑结构的不确定性而低估结构的地震风险性。 相似文献
7.
In the present study, probabilistic seismic hazard assessment was conducted for Cyprus based on several new results: a new
comprehensive earthquake catalog, seismic source models based on new research, and new attenuation relationships. Peak ground
acceleration distributions obtained for a return period of 475 years for rock conditions indicate high hazard along the southern
coastline of Cyprus, where the expected ground motion is between 0.3 and 0.4 g. The rest of the island is characterized by
values representing less severe shaking. Results of this study strongly indicate the inadequacy of the Turkish Earthquake
Code that is being used in the northern part of the island and the Eurocode 8 that is in effect in the southern part of the
island to approximate the uniform hazard spectra developed for the high hazard and moderate hazard regions of the island. 相似文献
8.
Using the ground motion attenuation relation, we calculated and compared the effective peak acceleration (EPA) generated by main shocks and their strong aftershocks of 21 earthquake sequences with MS≥7 occurred in Chinese mainland and offing of China during 1966~2002. The result shows that EPA of strong aftershocks usually exceed that of main shock for 76.2% earthquake sequences and EPA of more than 50% strong aftershocks are greatly lar-ger than that of main shocks in large area, which suggests that it is necessary to take damage produced by strong aftershock into account in the probabilistic seismic hazard analysis and the seismic design. 相似文献
9.
论汶川8．0级地震前的地震活动及趋势估计问题 总被引：1，自引：1，他引：0
本文对汶川8．0级地震前南北地震带大震轮回、首发大震、地震平静或空区、地震条带等地震活动图像在震前分析的基础上就地震预测问题进行了思考。地震活动图像在蕴震过程或阶段的估计只能是背景或中期预测的意义。同时指出区域地震活动图像在大范围多构造区的蕴震态分析中的复杂性。 相似文献
10.
This paper presents the results of research in reliability of short seismic links in shear based on tests. Four types of short links were analysed, each having the same cross section and the same length, but with different number of web stiffeners. The main purpose of the stiffeners is to preserve buckling of the seismic link web, i.e. to achieve plastification of the cross section by shear. The design model of shear resistance according to Eurocode 8 is applicable only to short links without web stiffeners. By adding the web stiffeners nonlinear inelastic behaviour of short seismic links differs depending on the number of stiffeners, so that the calculation model of shear resistance according to Eurocode 8 for short seismic link with stiffeners should be improved. This fact is considered by introducing the improve factors that were determined from the laboratory tests conducted on 16 specimens. On the base of tests in the second part of this paper the reliability of short seismic link is performed by forming limit state equations. These equations are formed by using the stochastic model, i.e. by describing the statistical nature of basic variables calculating the reliability index as an operational value of failure probability. The reliability level was determined by using the probabilistic analysis based on the first order reliability method which resulted with the conclusion that the short seismic links with two and three couples of web stiffeners designed according to requirements of Eurocode 8 have enough reliability for the reliability class RC2 and the mean recurrence interval of 50 years. 相似文献
11.
In the presented practice‐oriented probabilistic approach for the seismic performance assessment of building structures, the SAC‐FEMA method, which is a part of the broader PEER probabilistic framework and permits probability assessment in closed form, is combined with the pushover‐based N2 method. The most demanding part of the PEER probabilistic framework, that is incremental dynamic analysis, is replaced by the much simpler N2 method, which requires considerably less input data and much less computational time, but which can, nevertheless, often provide: acceptable estimates for the mean values of the structural response. Using some additional simplifying assumptions that are consistent with seismic code procedures, an explicit equation for a quick estimation of the annual probability of “failure” (i.e. the probability of exceeding the near collapse limit state) of a structure can be derived, which is appropriate for practical applications, provided that predetermined default values for the dispersion measures are available. In the paper, this simplified approach is summarized and applied to the estimation of the “failure” probability of reinforced concrete frame buildings representing both old structures, not designed for earthquake resistance, and new structures designed according to Eurocode 8. The results of the analyses indicate a high probability of the “failure” of buildings, which have not been designed for seismic loads. For a building designed according to a modern code, the conservatively determined probability of “failure” is about 30 times less but still significant (about 1% over the lifetime of the structure). Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
12.
A multi‐level seismic vulnerability assessment of reinforced concrete moment frame buildings located in moderate seismic zones (0.25g) is performed on a set of ductile versions of low‐ to mid‐rise two‐dimensional moment frames. The study is illustrated through application to comparative trial designs of two (4‐ and 8‐story) buildings adopting both space‐ and perimeter‐framed approaches. All frames are dimensioned as per the emerging version of the seismic design code in Egypt. These new seismic provisions are in line with current European norms for seismic design of buildings. Code‐compliant designs (CCD), as well as a proposed modified code design relaxing design drift demands for the investigated buildings, are examined to test their effectiveness and reliability. Applying nonlinear inelastic incremental dynamic analyses, fragility curves (FC) for the frames are developed corresponding to various code‐specified performance levels. Code preset lower and upper bounds on design acceleration and drift, respectively, are also addressed along with their implications, if imposed, on the frames seismic performance and vulnerability. Annual spectral acceleration hazard curves for the case study frames are also generated. Estimates for mean annual frequency (MAF) of exceeding various performance levels are then computed through an integration process of the data resulting from the FC with the site hazard curves. The study demonstrates that the proposed design procedure relaxing design drift demands delivers more economic building designs relative to CCDs, yet without risking the global safety of the structure. The relaxed design technique suggested herein, even though scoring higher, as expected by intuition, MAF of exceeding various code‐limiting performance levels expressed in terms of interstory drift ratios, still guarantees a reasonably acceptable actual margin against violating code limits for such levels. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
13.
Esther Hintersberger Frank Scherbaum Sebastian Hainzl 《Bulletin of Earthquake Engineering》2007,5(1):1-16
Scherbaum et al. [(2004) Bull Seismolo Soc Am 94(6): 2164–2185] proposed a likelihood-based approach to select and rank ground-motion
models for seismic hazard analysis in regions of low-seismicity. The results of their analysis were first used within the
PEGASOS project [Abrahamson et al. (2002), In Proceedings of the 12 ECEE, London, 2002, Paper no. 633] so far the only application
of a probabilistic seismic hazard analysis (PSHA) in Europe which was based on a SSHAC Level 4 procedure [(Budnitz et al.
1997, Recommendations for PSHA: guidance on uncertainty and use of experts. No. NUREG/CR-6372-V1). The outcome of this project
have generated considerable discussion (Klügel 2005, Eng Geol 78:285–307, 2005b) Eng Geol 78: 285–307, (2005c) Eng Geol 82:
79–85 Musson et al. (2005) Eng Geol 82(1): 43–55]; Budnitz et al. (2005), Eng Geol 78(3–4): 285–307], a central part of which
is related to the issue of ground-motion model selection and ranking. Since at the time of the study by Scherbaum et al. [(2004.)
Bull Seismolo Soc Am 94(6): 2164–2185], only records from one earthquake were available for the study area, here we test the
stability of their results using more recent data. Increasing the data set from 12 records of one earthquake in Scherbaum
et al. [(2004) Bull Seismolo Soc Am 94(6): 2164–2185] to 61 records of 5 earthquakes, which have mainly occurred since the
publication of the original study, does not change the set of the three top-ranked ground-motion models [Abrahamson and Silva
(1997) Seismolo Res Latt 68(1): 94–127; Lussou et al. (2001) J Earthquake Eng 5(1):13–33; Berge-Thierry et al. (2003) Bull
Seismolog Soc Am 95(2): 377–389. Only for the lower-ranked models do we obtain modifications in the ranking order. Furthermore,
the records from the Waldkirch earthquake (Dec, 5th, 2004, M
w = 4.9) enabled us to develop a new stochastic model parameter set for the application of Campbell’s [(2003) Bull Seismolo
Soc Am 93(3): 1012–1033] hybrid empirical model to SW Germany and neighbouring regions. 相似文献
14.
基于位移的概率极限状态设计 总被引：1，自引：0，他引：1
尽管近年来国内外学者提出了多种基于位移的抗震设计方法，但采用的与位移相关的反应谱大多是平均谱，设计过程可以看作是确定性的。基于位移的抗震设计应该建立在可靠度理论基础之上。利用作者在概率延性需求谱方面已有的研究成果和可靠度分析方法——验算点法，本文提出了根据基于位移的目标可靠指标直接进行结构设计的方法，并给出了设计流程图。为便于工程应用，在进行了大量分析计算之后，本文建议了基于位移的概率极限状态分项系数设计表达式，并确定了其中的分项系数。最后，本文对一8层框架结构采用建议的分项系数设计表达式进行了设计，并对有待于进一步研究的问题进行了简要分析。 相似文献
15.
Over the last two decades, the probabilistic assessment of reinforced concrete (RC) structures under seismic hazard has been developed rapidly. However, little attention has been devoted to the assessment of the seismic reliability of corroded structures. For the life‐cycle assessment of RC structures in a marine environment and earthquake‐prone regions, the effect of corrosion due to airborne chlorides on the seismic capacity needs to be taken into consideration. Also, the effect of the type of corrosive environment on the seismic capacity of RC structures has to be quantified. In this paper, the evaluation of the displacement ductility capacity based on the buckling model of longitudinal rebars in corroded RC bridge piers is established, and a novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life‐cycle seismic reliability assessment of these piers is proposed. The seismic demand depends on the results of seismic hazard assessment, whereas the deterioration of seismic capacity depends on the hazard associated with airborne chlorides. In an illustrative example, an RC bridge pier was modeled as single degree of freedom (SDOF). The longitudinal rebars buckling of this pier was considered as the sole limit state when estimating its failure probability. The findings show that the life‐cycle reliability of RC bridge piers depends on both the seismic and airborne chloride hazards, and that the cumulative‐time failure probabilities of RC bridge piers located in seismic zones can be dramatically affected by the effect of airborne chlorides. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
16.
The paper aims to evaluate the way Eurocode 8 treats the consideration of asynchronous earthquake ground motion during the
seismic design of bridges, and to discuss alternative solutions for cases wherein existing provisions do not lead to satisfactory
results. The evaluation of EC8-2 new provisions and simplified methods is performed through comparison with a more refined
approach whereas an effort is made to quantitatively assess the relative importance of various design and analysis assumptions
that have to be made when spatial variability of ground motion is taken into consideration, based on the study of the dynamic
response of 27 different bridges. It is concluded that, despite the complexity of the problem, there are specific cases where
EC8 provisions can be safely and easily applied in practice, while in other cases ignoring the effect of asynchronous excitation
or performing simplified calculations can significantly underestimate the actual seismic demand. 相似文献
17.
分析后认为,从1999年开始龙门山断裂带上地震活动增强,并持续到2008年5月12日汶川8级地震发生前一个多月。地震活动的增强主要以最大地震的震级为3、4级的小震群活动的方式表现。2006年至2008年3月间,有两个小震群出现在汶川8.0大震震中附近。小震群地震震源机制的结果表明,随时间接近汶川8.0级大震发生,小震群的震源机制趋向一致,这些在空间分布不均匀的密集小破裂逐渐成定向有规律地排列,有利于裂隙的进一步扩展贯通,形成大破裂。 相似文献
18.
In this paper, we calculated the seismic pattern of instrumental recorded small and moderate earthquakes near the epicenter of the 1303 Hongtong M=8 earthquake, Shanxi Province. According to the spatial distribution of small and moderate earthquakes, 6 seismic dense zones are delineated. Temporal distribution of ML≥2 earthquakes since 1970 in each seismic dense zone has been analyzed. Based on temporal distribution characteristics and historical earthquake activity, three types of seismicities are proposed. The relationship between seismic types and crustal medium is analyzed. The mechanism of three types is discussed. Finity of strong earthquake recurrence is proposed. Seismic hazard in mid-long term and diversity of earthquake disaster in Shanxi seismic belt are discussed. 相似文献
19.
20.
Displacement capacity of masonry buildings as a basis for the assessment of behavior factor: an experimental study 总被引：3，自引：2，他引：1
The results of shaking table tests of a series of 1:5 scale masonry building models have been used for the assessment of values
of structural behavior factor q for masonry structures, seismic force reduction factors proposed for the calculation of design seismic loads by Eurocode
8, European standard for the design of structures for earthquake resistance. Six models have been tested, representing prototype
buildings of two different structural configurations and built with two different types of masonry materials. The study indicated
that the reduction of seismic forces for the design depends not only on the type of masonry construction system, but also
on structural configuration and mechanical characteristics of masonry materials. It has been also shown that besides displacement
and energy dissipation capacity, damage limitation requirement should be taken into account when evaluating the values of
behavior factor. On the basis of analysis of experimental results a conclusion can be made, that the values at the upper limit
of the proposed range of values of structural behavior factor q for unreinforced and confined masonry construction systems are adequate, if pushover methods are used and the calculated
global ductility of the structure is compared with the displacement demand. In the case where elastic analysis methods are
used and significant overstrength is expected, the proposed values are conservative. However, additional research and parametric
studies are needed to propose the modifications. 相似文献