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1.
规则桥梁抗震性能水准的定义及其量化描述 总被引：1，自引：0，他引：1
基于性能的结构抗震设计是各国结构抗震设计规范未来的主要发展方向,虽然其理论框架已基本形成,然而其中至关重要的结构抗震性能水准的定义及其量化描述问题,目前仍处于研究探讨阶段.本文从公路梁式桥震害现象出发,采用极限状态设计概念,对规则桥梁在地震作用下的性能水准予以明确的定义;并以墩顶漂移率作为设计参数,通过对大量试验数据的... 相似文献
2.
现代抗震设计理论的发展过程 总被引：18，自引：0，他引：18
介绍了现代抗震设计理论的发展过程，基于性态的抗震设计理论的提出背景、发展情况及研究内容；详细介绍了基于性态的抗震设计理论的抗震设防方法；指出了基于性态的抗震设计理论与传统抗震设计理论的主要区别及特点。 相似文献
3.
Conventional design methodology for the earthquake‐resistant structures is based on the concept of ensuring ‘no collapse’ during the most severe earthquake event. This methodology does not envisage the possibility of continuous damage accumulation during several not‐so‐severe earthquake events, as may be the case in the areas of moderate to high seismicity, particularly when it is economically infeasible to carry out repairs after damaging events. As a result, the structure may collapse or may necessitate large scale repairs much before the design life of the structure is over. This study considers the use of design force ratio (DFR) spectrum for taking an informed decision on the extent to which yield strength levels should be raised to avoid such a scenario. DFR spectrum gives the ratios by which the yield strength levels of single‐degree‐of‐freedom oscillators of different initial periods should be increased in order to limit the total damage caused by all earthquake events during the lifetime to a specified level. The DFR spectra are compared for three different seismicity models in case of elasto‐plastic oscillators: one corresponding to the exponential distribution for return periods of large events and the other two corresponding to the lognormal and Weibull distributions. It is shown through numerical study for a hypothetical seismic region that the use of simple exponential model may be acceptable only for small values of the seismic gap length. For moderately large to large seismic gap lengths, it may be conservative to use the lognormal model, while the Weibull model may be assumed for very large seismic gap lengths. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
4.
耗能梁段作为偏心支撑结构的耗能元件，在大震作用下通过弹塑性变形吸收地震能量，保护主体结构处于弹性受力状态。现行规范基于强度的设计理论，为了保证耗能梁段进入塑性或破坏，梁柱构件需要进行放大内力设计，导致截面过大，而且基于强度的设计方法很难保证结构的整体破坏状态。目前，抗震设计越来越重视基于性能的设计思想，该方法能够评估结构的弹塑性反应。对于高强钢组合偏心支撑，其中耗能梁段和支撑采用Q345钢，框架梁柱采用Q460或者Q690高强度钢材，高强钢不仅带来良好的经济效益，而且能够推广高强钢在抗震设防区的应用。利用基于性能设计方法设计了4种不同形式的高强钢组合偏心支撑钢框架，包括K形、Y形、V形和D形，考虑4层、8层、12层和16层的影响。通过Pushover分析和非线性时程分析评估该结构的抗震性能，研究结果表明:4种形式的高强钢组合偏心支撑钢框架具有类似的抗震性能，在罕遇地震作用下，几乎所有耗能梁段均参与耗能，而且层间侧移与耗能梁段转角沿高度分布较为均匀。其中:D形偏心支撑具有最大的抗侧刚度，但延性较差，而Y形偏心支撑的抗侧刚度最弱，但延性最佳。 相似文献
5.
Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis. 相似文献
6.
The linked column frame (LCF) system is proposed as a seismic load resisting system that uses conventional components to limit seismic damage to relatively easily replaced elements. The LCF features a primary lateral system, denoted the linked column, which is made up of dual columns connected with replaceable links, and a secondary flexible moment frame system with beams having fully restrained connections at one end and simple connections at the other. The linked columns are designed to limit seismic forces and provide energy dissipation via link yielding, while preventing damage to the moment frame under certain earthquake hazard levels. A design procedure is proposed that ensures plastic hinges develop in the links of the linked columns at a significantly lower story drift than when plastic hinges develop in the moment frame beams. The large drift difference helps enable design of this system for two distinct performance states: rapid return to occupancy, where only link damage occurs and relatively simple link replacement is possible, and collapse prevention, where both the links and the beams of the moment frame may be damaged. A series of 3‐story, 6‐story, and 9‐story prototype LCF buildings were designed using the proposed design approach. Nonlinear models were developed for the designs with the link models validated using recent experimental results. The seismic response of these systems was investigated for ground motions representing various seismic hazard levels. Results show that the LCF system not only provides collapse prevention, but also has the capability of limiting economic loss by reducing structural damage and allowing for rapid return to occupancy following earthquakes with shorter return periods. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
With the increasing emphasis of performance‐based earthquake engineering in the engineering community, several investigations have been presented outlining simplified approaches suitable for performance‐based seismic design (PBSD). Central to most of these PBSD approaches is the use of closed‐form analytical solutions to the probabilistic integral equations representing the rate of exceedance of key performance measures. Situations where such closed‐form solutions are not appropriate primarily relate to the problem of extrapolation outside of the region in which parameters of the closed‐form solution are fit. This study presents a critical review of the closed‐form solution for the annual rate of structural collapse. The closed‐form solution requires the assumptions of lognormality of the collapse fragility and power model form of the ground motion hazard, of which the latter is more significant regarding the error of the closed‐form solution. Via a parametric study, the key variables contributing to the error between the closed‐form solution and solution via numerical integration are illustrated. As these key variables cannot be easily measured, it casts doubt on the use of such closed‐form solutions in future PBSD, especially considering the simple and efficient nature of using direct numerical integration to obtain the solution. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
8.
Y. H. Chai 《地震工程与结构动力学》2005,34(1):83-96
Seismic performance of structures is related to the damage inflicted on the structure by the earthquake, which means that formulation of performance‐based design is inherently coupled with damage assessment of the structure. Although the potential for cumulative damage during a long‐duration earthquake is generally recognized, most design codes do not explicitly take into account the damage potential of such events. In this paper, the classical low‐cycle fatigue model commonly used for seismic damage assessment is cast in a framework suitable for incorporating cumulative damage into seismic design. The model, in conjunction with a seismic input energy spectrum, may be used to establish an energy‐based seismic design. In order to ensure satisfactory performance in a structure, the cyclic plastic strain energy capacity of the structure is designed to be larger than or equal to the portion of seismic input energy contributing to cumulative damage. The resulting design spectrum, which depends on the duration of the ground motion, indicates that the lateral strength of the structure must be increased in order to compensate for the increased damage due to an increased number of inelastic cycles that occur in a long‐duration ground motion. Examples of duration‐dependent inelastic design spectra are developed using parameters currently available for the low‐cycle fatigue model. The resulting spectra are also compared with spectra developed using a different cumulative damage model. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
9.
Comparison of seismic actions and structural design requirements in Chinese code GB 50011 and international standard ISO 3010 总被引：1，自引：0，他引：1
王亚勇 《地震工程与工程振动(英文版)》2004,3(1):1-9
This paper presents a comparison between the Chinese Code GB50011-2001 and the International Standard ISO3010: 2001(E), emphasizing the similarities and differences related to design requirements, seismic actions and analytical approaches. Similarities include: earthquake return period, conceptual design, site classification, structural strength and ductility requirements, deformation limits, response spectra, seismic analysis procedures, isolation and energy dissipation, and nonstructural elements. Differences exist in the following areas: seismic levels, earthquake loading, mode damping factors and structural control. 相似文献
10.
Optimum seismic design of reinforced concrete frames according to Eurocode 8 and fib Model Code 2010 
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下载免费PDF全文 Panagiotis E. Mergos 《地震工程与结构动力学》2017,46(7):1181-1201
Traditional seismic design, like the one adopted in Eurocode 8 (EC8), is force‐based and examining a single level of seismic action. In order to provide improved control of structural damage for different levels of seismic action, the new fib Model Code 2010 (MC2010) includes a fully fledged displacement‐based and performance‐based seismic design methodology. However, the level of complexity and computational effort of the MC2010 methodology is significantly increased. Hence, the use of automated optimization techniques for obtaining cost‐effective design solutions becomes appealing if not necessary. This study employs genetic algorithms to derive and compare optimum seismic design solutions of reinforced concrete frames according to EC8 and MC2010. This is important because MC2010 is meant to serve as a basis for future seismic design codes. It is found that MC2010 drives to more cost‐effective solutions than EC8 for regions of low seismicity and better or similar costs for regions of moderate seismicity. For high‐seismicity regions, MC2010 may yield similar or increased structural costs. This depends strongly on the provisions adopted for selecting the set of ground motions. In all cases, MC2010 provides enhanced control of structural damage. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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12.
Modified seismic design of concentrically braced frames considering flexural demand on columns 下载免费PDF全文
下载免费PDF全文 Special concentrically braced frames (SCBFs) are considered as one of the most economical and effective lateral force‐resisting systems in structures located in the regions of high seismicity. Steel braces in a braced frame undergo large axial deformations in tension and compression to dissipate the seismic energy. However, past studies have shown that SCBFs exhibit the soft‐story hinge mechanisms and unpredictable failure patterns under earthquake loading conditions. These inelastic responses along with the use of continuous structural sections as columns over consecutive floors induce flexural demand that is not considered in the current design practice. In this study, the evaluation of seismic performance of nine SCBFs designed as per the current practice has been carried out for three different story heights (i.e., three‐story, six‐story, and nine‐story) and three types of brace configurations (namely, chevron, split X, and single X). Three additional design techniques are also explored based on (i) the inclusion of column moments in the design; (ii) the theory of formation of plastic hinges; and (iii) the design of braces considering the forces computed at their post‐buckled stages. Nonlinear dynamic analyses of these study frames have been evaluated numerically using a computer software Perform‐3D for a suite of 40 ground motions representing the design basis earthquake and maximum considered earthquake hazard levels. Analyses results showed that the SCBFs designed as per the modified procedures achieved the desired performance objectives without the formation of soft‐story mechanism. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
13.
The use of nonlinear static procedures for performance‐based seismic design (PBSD) and assessment is a well‐established practice, which has found its way into modern codes for quite some time. On the other hand, near‐source (NS) ground motions are receiving increasing attention, because they can carry seismic demand systematically different and larger than that of the so‐called ordinary records. This is due to phenomena such as rupture forward directivity (FD), which can lead to distinct pulses appearing in the velocity time‐history of the ground motion. The framework necessary for taking FD into account in probabilistic seismic hazard analysis (PSHA) has recently been established. The objective of the present study is to discuss the extension of nonlinear static procedures, specifically the displacement coefficient method (DCM), with respect to the inelastic demand associated with FD. In this context, a methodology is presented for the implementation of the DCM toward estimating NS seismic demand, by making use of the results of NS‐PSHA and a semi‐empirical equation for NS‐FD inelastic displacement ratio. An illustrative application of the DCM, with explicit inclusion of NS‐pulse‐like effects, is given for a set of typical plane R/C frames designed under Eurocode provisions. Different scenarios are considered in the application and nonlinear dynamic analysis results are obtained and discussed with respect to the static procedure estimates. Conclusions drawn from the results may help to assess the importance of incorporating NS effects in PBSD. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
14.
随着地震工程学的发展和结构抗震设计思想和理论的进步,探讨结构在地震作用下的地震损伤破坏机理和基于结构性能的抗震设计方法(PBSD)逐渐得到了各国专家、学者的重视。而地震损伤评估的研究就是其中的一个重要方向。鉴于现阶段混凝土结构地震损伤评估方法的局限性,本文采用推广的混凝土材料的Mazars损伤模型,进而提出了一种基于常规有限元分析荷载子步的简化的地震损伤评估方法,这种方法实现简单,便于实际工程应用,同时具有一定的精细性。最后,将本文的损伤评估方法应用到一个钢筋混凝土框架的地震损伤评估实例中,分析结果与实验和实际的震害比较吻合,表明本文提出的模型和方法是有效的。 相似文献
15.
As high‐rise buildings are built taller and more slender, their dynamic behavior becomes an increasingly critical design consideration. Wind‐induced vibrations cause an increase in the lateral wind design loads, but more importantly, they can be perceived by building occupants, creating levels of discomfort ranging from minor annoyance to severe motion sickness. The current techniques to address wind vibration perception include stiffening the lateral load‐resisting system, adding mass to the building, reducing the number of stories, or incorporating a vibration absorber at the top of the building; each solution has significant economic consequences for builders. Significant distributed damage is also expected in tall buildings under severe seismic loading, as a result of the ductile seismic design philosophy that is widely used for such structures. In this paper, the viscoelastic coupling damper (VCD) that was developed at the University of Toronto to increase the level of inherent damping of tall coupled shear wall buildings to control wind‐induced and earthquake‐induced dynamic vibrations is introduced. Damping is provided by incorporating VCDs in lieu of coupling beams in common structural configurations and therefore does not occupy any valuable architectural space, while mitigating building tenant vibration perception problems and reducing both the wind and earthquake responses of the structure. This paper provides an overview of this newly proposed system, its development, and its performance benefits as well as the overall seismic and wind design philosophy that it encompasses. Two tall building case studies incorporating VCDs are presented to demonstrate how the system results in more efficient designs. In the examples that are presented, the focus is on the wind and moderate earthquake responses that often govern the design of such tall slender structures while reference is made to other studies where the response of the system under severe seismic loading conditions is examined in more detail and where results from tests conducted on the viscoelastic material and the VCDs in full‐scale are presented. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
Simplified approaches for examining structural system response under sequential earthquake and tsunami loading are helpful for understanding response trends. To aid understanding, nonlinear (constant‐ductility) response spectra are developed for elastoplastic single degree of freedom systems subjected to seismic loads followed by hydrodynamic tsunami loads. The forcing function is composed of long‐duration earthquake motion concatenated with a range of tsunami hydrodynamic forces that are proportional to the pseudo‐spectral acceleration produced by the earthquake motion. The constant‐ductility spectra are thus constructed for scenarios where the loading imposed by one hazard is not dominant over the other. The spectra and basic intensity measures indicate that the amplification of response for sequential earthquake and tsunami loading over the earthquake only case is most significant for systems with long natural periods and high‐ductility capacity under seismic loading. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
17.
钢筋混凝土框架中震可修标准及简化抗震设计方法 总被引：4，自引：1，他引：4
本文对国际上主要建筑抗震设计规范中钢筋混凝土框架可修水准的层间位移角限值进行了比较,讨论了国内的一些相关研究结果,结合中国抗震规范确定钢筋混凝土框架中震可修层间位移角限值和屋顶侧移率限值分别为1/150和1/200。采用安全系数的抗震设计表达、论述了对应于结构层间位移角基于承载力的简化抗震设计方法。最后用实例按反应谱分析和弹性时程分析验证了钢筋混凝土框架中震可修层间位移角限值的有效控制作用,初步确定了简化抗震设计方法中梁柱构件的抗震安全系数并分析了提高目前结构抗震安全度的措施。 相似文献
18.
This paper assesses the influence of cyclic and in‐cycle degradation on seismic drift demands in moment‐resisting steel frames (MRF) designed to Eurocode 8. The structural characteristics, ground motion frequency content, and level of inelasticity are the primary parameters considered. A set of single‐degree‐of‐freedom (SDOF) systems, subjected to varying levels of inelastic demands, is initially investigated followed by an extensive study on multi‐storey frames. The latter comprises a large number of incremental dynamic analyses (IDA) on 12 frames modelled with or without consideration of degradation effects. A suite of 56 far‐field ground motion records, appropriately scaled to simulate 4 levels of inelastic demand, is employed for the IDA. Characteristic results from a detailed parametric investigation show that maximum response in terms of global and inter‐storey drifts is notably affected by degradation phenomena, in addition to the earthquake frequency content and the scaled inelastic demands. Consistently, both SDOF and frame systems with fundamental periods shorter than the mean period of ground motion can experience higher lateral strength demands and seismic drifts than those of non‐degrading counterparts in the same period range. Also, degrading multi‐storey frames can exhibit distinctly different plastic mechanisms with concentration of drifts at lower levels. Importantly, degrading systems might reach a “near‐collapse” limit state at ductility demand levels comparable to or lower than the assumed design behaviour factor, a result with direct consequences on optimised design situations where over‐strength would be minimal. Finally, the implications of the findings with respect to design‐level limit states are discussed. 相似文献
19.
Probabilistically controlled design values of the nonlinear seismic response of reinforced concrete frames are obtained using a method previously proposed by the authors. The method allows to calculate conservative design values characterized by a predefined non‐exceedance probability, using a limited number of spectrum‐fitting generated accelerograms. Herein the method is applied to elastic‐strain hardening single degree of freedom systems representative of RC framed structures and is then assessed with reference to four reinforced concrete model frames designed according to EC8. The frames are characterized by different natural periods and aspect ratios. The results, compared with those obtained applying current EC8 recommendations, show the effectiveness of the proposed method. EC8 provides for design values of the seismic response of a structure with a nonlinear behavior computed as the mean value of the responses to seven accelerograms or as the maximum value of the responses to three accelerograms. These two criteria lead to design values characterized by very different and uncontrolled non‐exceedance probability levels, while the proposed method allows the analyst to directly control the non‐exceedance probability level of the calculated design values. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献