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1.
Aman Mwafy 《地震工程与工程振动(英文版)》2011,10(1):115-127
To verify the seismic design response factors of high-rise buildings, five reference structures, varying in height from 20- to 60-stories, were selected and designed according to modern design codes to represent a wide range of concrete wall structures. Verified fiber-based analytical models for inelastic simulation were developed, considering the geometric nonlinearity and material inelasticity of the structural members. The ground motion uncertainty was accounted for by employing 20 earthquake records representing two seismic scenarios, consistent with the latest understanding of the tectonic setting and seismicity of the selected reference region (UAE). A large number of Inelastic Pushover Analyses (IPAs) and Incremental Dynamic Collapse Analyses (IDCAs) were deployed for the reference structures to estimate the seismic design response factors. It is concluded that the factors adopted by the design code are adequately conservative. The results of this systematic assessment of seismic design response factors apply to a wide variety of contemporary concrete wall buildings with various characteristics. 相似文献
2.
In recent years, several research groups have studied a new generation of analysis methods for seismic response assessment of existing buildings. Nevertheless, many important developments are still needed in order to define more reliable and effective assessment procedures. Moreover, regarding existing buildings, it should be highlighted that due to the low knowledge level, the linear elastic analysis is the only analysis method allowed. The same codes (such as NTC2008, EC8) consider the linear dynamic analysis with behavior factor as the reference method for the evaluation of seismic demand. This type of analysis is based on a linear-elastic structural model subject to a design spectrum, obtained by reducing the elastic spectrum through a behavior factor. The behavior factor (reduction factor or q factor in some codes) is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural capacities. The behavior factors should be defined based on several parameters that influence the seismic nonlinear capacity, such as mechanical materials characteristics, structural system, irregularity and design procedures. In practical applications, there is still an evident lack of detailed rules and accurate behavior factor values adequate for existing buildings. In this work, some investigations of the seismic capacity of the main existing RC-MRF building types have been carried out. In order to make a correct evaluation of the seismic force demand, actual behavior factor values coherent with force based seismic safety assessment procedure have been proposed and compared with the values reported in the Italian seismic code, NTC08. 相似文献
3.
Seismic safety of low ductility structures used in Spain 总被引：1，自引：0，他引：1
The most important aspects of the design, seismic damage evaluation and safety assessment of structures with low ductility
like waffle slabs buildings or flat beams framed buildings are examined in this work. These reinforced concrete structural
typologies are the most used in Spain for new buildings but many seismic codes do not recommend them in seismic areas. Their
expected seismic performance and safety are evaluated herein by means of incremental non linear structural analysis (pushover
analysis) and incremental dynamic analysis which provides capacity curves allowing evaluating their seismic behavior. The
seismic hazard is described by means of the reduced 5% damped elastic response spectrum of the Spanish seismic design code.
The most important results of the study are the fragility curves calculated for the mentioned building types, which allow
obtaining the probability of different damage states of the structures as well as damage probability matrices. The results,
which show high vulnerability of the studied low ductility building classes, are compared with those corresponding to ductile
framed structures. 相似文献
4.
Nikos D Lagaros 《地震工程与工程振动(英文版)》2008,7(1):45-56
5.
Performance-Based Seismic Design is now widely recognized as the pre-eminent seismic design and assessment methodology for
building structures. In recognition of this, seismic codes may require that buildings achieve multiple performance objectives
such as withstanding moderate, yet frequently occurring earthquakes with minimal structural and non-structural damage, while
withstanding severe, but rare earthquakes without collapse and loss of life. These objectives are presumed to be satisfied
by some codes if the force-based design procedures are followed. This paper investigates the efficacy of the Eurocode 8 force-based
design provisions with respect to RC frame building design and expected seismic performance. Four, eight, and 16-storey moment
frame buildings were designed and analyzed using the code modal response spectrum analysis provisions. Non-linear time-history
analyses were subsequently performed to determine the simulated seismic response of the structures and to validate the Eurocode
8 force-based designs. The results indicate the design of flexural members in medium-to-long period structures is not significantly
influenced by the choice of effective member stiffness; however, calculated interstorey drift demands are significantly affected.
This finding was primarily attributed to the code’s enforcement of a minimum spectral ordinate on the design spectrum. Furthermore,
design storey forces and interstorey drift demand estimates (and therefore damage), obtained by application of the code force-based
design procedure varied substantially from those found through non-linear time-history analysis. Overall, the results suggest
that though the Eurocode 8 may yield life-safe designs, the seismic performance of frame buildings of the same type and ductility
class can be highly non-uniform. 相似文献
6.
选取按照现行规范设计的既有建筑进行有限元建模,考虑地震动的不确定性对其进行大量增量动力分析(IDA),得到模型的IDA曲线簇。在此基础上对其进行地震需求概率分析和概率抗震能力分析,拟合得到结构的易损性曲线,据此对结构的倒塌概率进行定量评估,并比较基于非线性分析与性能评估软件PERFORM-3D的纤维模型和塑性铰模型的分析结果。结果表明:按照我国现行规范设计的钢筋混凝土(RC)框架结构,在预期的罕遇地震作用下倒塌概率较小,可满足"大震不倒"的要求;基于PERFORM-3D的截面纤维模型所得的RC框架结构,经非线性分析所得的倒塌概率相对保守,安全储备更高。 相似文献
7.
首先输入多条实际竖向地震记录,用时程分析考察了塔楼高度和连体跨度不同的多个算例。然后将其抽象成塔楼和连体桁架组成的双自由度体系,运用频域分析方法,得到竖向地震作用的变化规律：11随着桁架对塔楼频率比增加,连体地震放大作用越明显;2）当连体对塔楼质量比较小且两者频率比相近1,连体地震反应进一步加强。现行抗震规范的重力系数法提出的大跨度结构竖向地震的实用计算公式对于本文研究结构并不完全适用。提出考虑塔楼和桁架协同地震作用的实用算式,并对一个超高层工程实例进行竖向地震作用分析,与时程分析结果吻合较好。 相似文献
8.
Angelo Masi 《Bulletin of Earthquake Engineering》2003,1(3):371-395
The seismic vulnerability of some frame structures, typical of existing Reinforced Concrete buildings designed only to vertical
loads, has been evaluated. They are representative of building types widely present in the Italian building stock of the last
30 years. A simulated design of the structures has been made with reference to the codes in force, the available handbooks
and the current practice at the time of construction. The seismic response is calculated through non linear dynamic analyses
with artificial and natural accelerograms. Three main types have been examined: bare frames, regularly infilled frames and
pilotis frames. The results show a high vulnerability for the pilotis buildings: they can be assigned to the class B of the
European Macroseismic Scale of 1998 (EMS98). On the contrary, a low vulnerability (class D of EMS98) can be attributed to
the regularly infilled buildings: in this case collapse can be considered unlikely also with strong earthquakes. An intermediate
seismic behavior is shown by buildings without infills, whose vulnerability can be placed between the classes B and C of EMS98.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
A study is made of the dynamic torsional response of a single mass partially symmetric system to ground excitation. Using the response spectrum technique, the torsional response and dynamic eccentricity are determined as functions of the eccentricity of the system and its uncoupled frequency ratio. It is shown that the dynamic eccentricity can best be expressed as a bilinear function of eccentricity. For the critical condition which occurs when the uncoupled frequency ratio is unity, a comparison is made with the torsional provisions of five seismic codes (Canada, Mexico, New Zealand, ATC3 and Germany). It is shown that the first four codes underestimate the torsional moment, and also the edge displacement of the system, significantly when the eccentricity is small and the uncouped torsional and lateral frequencies are close. 相似文献
10.
Gerardo M. Verderame Iunio Iervolino Gaetano Manfredi 《Bulletin of Earthquake Engineering》2010,8(4):955-972
The fundamental period has a primary role in seismic design and assessment as it is the main feature of the structure that allows one to determine the elastic demand and, indirectly, the required inelastic performance in static procedures. In fact, the definition of easy to manage relationships for the assessment of the elastic period has been the subject of a significant deal of both experimental and numerical/analytical studies, some of which have been acknowledged by codes and guidelines worldwide. Moreover, this kind of information is useful for territorial-scale seismic loss assessment methodologies. In the majority of cases, the assessment of the period is considered as function of the structural system classification and number of storeys or height. Reinforced concrete structures, comprising most of the building stock in Italy and in seismic prone areas in Europe and in the Mediterranean region, were built after the Second World War and are designed with obsolete seismic codes, if not for gravity loads only. Therefore, a class of buildings featuring the same height and/or number of storeys may show a significant variability of the structural system. This, along with the contribution of the stair module, may affect the elastic periods in the two main directions of a three-dimensional building. In the study presented these issues are investigated with reference to a population of existing RC structures designed acknowledging the practice at the time of supposed construction (e.g., simulated design) and with reference to the relative enforced code. The elastic period is evaluated for both main directions of the buildings of the considered sample, and regression analysis is employed to capture the dependency of the elastic dynamic properties of the structures as a function of mass and stiffness. 相似文献
11.
模型化方法对钢筋混凝土框架地震反应的影响分析 总被引：1，自引：0，他引：1
结构非线性动力分析平台OpenSees具备丰富的材料、单元、模型化方法等分析选项和强大的求解功能。在OpenSees平台,对按我国规范设计的八度区二级和九度区一级典型钢筋混凝土框架结构进行了一系列罕遇烈度地震作用下的非线性动力反应分析。通过对分析结果的对比、判断,并结合各种模型化方法对结构地震反应的影响方式进行解释,从顶点侧移、层间侧移角、基底剪力、框架塑性铰分布等方面揭示了不同单元力学模型以及箍筋、板筋对结构整体、局部地震反应的影响规律。 相似文献
12.
抗震设计规范中的场地设计反应谱是一般工程抗震设计的依据,各国的抗震设计规范对场地设计反应谱的规定不尽相同。主要表现在反应谱的形状和谱参数的差异。本文收集了若干国家的抗震设计规范;在总结各国抗震设计规范中关于场地设计反应谱规定的基础上,对中国、美国、日本、欧洲、土耳其和智利等有代表性的国家和地区的抗震设计规范进行分析和对比研究;总结了我国抗震设计规范场地设计反应谱的演化历史和发展过程;提出了进一步开展这一领域研究工作的若干建议,本文的工作对从事场地设计反应谱研究的科技人员有重要的参考价值。 相似文献
13.
A study is made of the dynamic behaviour of multistorey steel rigid-frame buildings with set-back towers. The effects of set-backs upon the building frequencies and mode shapes are examined. Then the effects of set-backs on seismic response are investigated by analysing the response of a series of set-back building frame models to the El Centro ground motion. Finally, the computed responses to the El Centro earthquake are compared with some code provisions dealing with the seismic design of set-back buildings. The conclusions derived from the study include the following:
- 1. The higher modes of vibration of a set-back building can make a very substantial contribution to its total seismic response; this contribution increases with the slenderness of the tower.
- 2. Some of the important response parameters for the tower portion of a set-back building are substantially larger than for a related uniform building.
- 3. For very slender towers, the transition region between the tower and the base may be subjected to very large storey shears.
14.
泳池式反应堆(简称泳池堆)是环境友好型的新型供热源，不同地基条件下反应堆厂房结构的地震响应是进行抗震设计的关键技术参考。以某堆型泳池式反应堆厂房为研究对象，基于ANSYS软件及UPFs的二次开发特点，建立考虑液晃效应的泳池堆-地基三维动力相互作用模型，其中，通过创建黏弹性边界单元来考虑散射波的能量耗散，采用Housner等效力学模型模拟动液压效应，从而开展不同地基对泳池堆厂房结构地震响应的影响分析。分析结果表明：当地基土的坚硬度、刚度逐渐减小时，泳池堆的地震响应变化明显，特别是由岩性地基逐渐变为土质地基时，结构的主应力和层间位移角逐渐增大，而加速度反应谱则逐渐减小。研究成果可为不同型号泳池堆的抗震设计提供有益的参考。 相似文献
15.
Recent researches have revealed that the seismic ground response above tunnels can be different from the free-field motion during earthquakes. Nevertheless, to the best of the authors׳ knowledge, neither building codes nor seismic microzonation guidelines have yet considered this matter. In the present study, the seismic response of a linear elastic medium including a buried unlined tunnel subjected to vertically propagating incident SV and P waves are addressed. For analysis purposes, a numerical time-domain analysis is performed by utilizing a robust numerical algorithm working based on the boundary element method. It is observed that the amplification of the ground surface underlain by a tunnel is increased in long periods. The variation of the amplification factor and characteristic period of the medium versus the buried depth of the tunnel are depicted as the major results of this study. Some simple and useful relations are proposed for estimating the seismic microzonation of the areas underlain by tunnels. These relations can also be used for the preliminary seismic design of structures located on underground structures. 相似文献
16.
A risk-targeted design spectral acceleration and the corresponding seismic design action for the force-based design of structures is introduced by means of two formulations. The first one called direct formulation utilizes the seismic hazard function at the site of the structure. Because the seismic action defined in the codes is often associated with a designated return period, an indirect formulation is also introduced. It incorporates a risk-targeted safety factor that can be used to define a risk-targeted reduction factor. It is shown that the proposed formulations give analogical results and provide an insight into the concept of the reduction of seismic forces for the force-based seismic design of structures if the objective is defined by a target collapse risk. The introduced closed-form solution for the risk-targeted reduction factor can be used to investigate how the target collapse risk, the seismic hazard parameters, the randomness of the seismic action, and the conventional parameters (ie, the overstrength factor and the deformation and energy dissipation capacity) affect the seismic design forces in the case of force-based design. However, collaborative research is needed in order to develop appropriate models of these parameters. In the second part of the paper, the proposed formulations are demonstrated by estimating the risk-targeted seismic design action for a six-storey reinforced concrete building. By verifying the collapse risk of the designed structure, it is demonstrated that the risk-targeted seismic action, in conjunction with a conventional force-based design, provided structure with acceptable performance when measured in terms of collapse risk. 相似文献
17.
Effect of depth of soil stratum on estimated inelastic displacement of three typical structures, viz. a four storey building, a continuous bridge, and a tower, is studied and adequacy of the site amplification models of the current design codes and available empirical relationships is examined. The structures are assumed to be located on well-defined sites with varying bedrock depths, and effect of depth on elastic response spectrum, site amplification factor, displacement modification factor and inelastic displacement is studied, numerically, for two values of PGA. It is observed that soil depth has a significant effect on elastic as well as inelastic response of the structures; however, the effect of soil amplification on inelastic response is not as pronounced as in case of elastic response. Therefore, use of empirical site amplification models based on elastic response may be too conservative, for estimating inelastic response. 相似文献
18.
Based on an asymmetric multistorey frame building model, this paper investigates the influence of a building's higher vibration modes on its inelastic torsional response and evaluates the adequacy of the provisions of current seismic building codes and the modal analysis procedure in accounting for increased ductility demand in frames situated at or near the stiff edge of such buildings. It is concluded that the influence of higher vibration modes on the response of the upper-storey columns of stiff-edge frames increases significantly with the building's fundamental uncoupled lateral period and the magnitude of the stiffness eccentricity. The application of the equivalent static torsional provisions of certain building codes may lead to non-conservative estimates of the peak ductility demand, particularly for structures with large stiffness eccentricity. In these cases, the critical elements are vulnerable to excessive additional ductility demand and, hence, may be subject to significantly more severe structural damage than in corresponding symmetric buildings. It is found that regularly asymmetric buildings excited well into the inelastic range may not be conservatively designed using linear elastic modal analysis theory. Particular caution is required when applying this method to the design of stiff-edge frame elements in highly asymmetric structures. 相似文献
19.
In this paper a probabilistic approach has been adopted to study both the effects of uncertainty in earthquake frequency content and the correlation between earthquake frequency content and ground motion intensity on the response of a single-storey torsionally coupled elastic structure. The earthquake ground motion has been assumed to be a Gaussian, zero mean, stationary random process which is fully characterized by a power spectrum. The ground acceleration power spectrum is idealized as a probabilistic normalized power spectrum computed from actual earthquake records. The advantage of such an idealization is that it enables the effect of the natural frequency as a controlling structural parameter in torsional coupling to be assessed. Comparisons of the dynamic amplifications of eccentricity with those obtained from modern codes of practice and conventional response spectrum analyses have been made. The results of this study have shown that the variation in the frequency content has a significant effect on the response of low frequency structures, while the correlation between the frequency content and the intensity of seismic ground motion is insignificant for the wide range of structures considered. The structure natural frequency has been shown to be an important controlling parameter in the torsionally coupled response of structures subject to seismic loading. The frequency dependence of the dynamic amplification of eccentricity was found not to be reflected in the response spectrum analysis and the torsional provisions of modern building codes. 相似文献
20.
Comparison of DSHA-based response spectrum with design response spectrum of building code of Pakistan (BCP-SP-2007) for a site in Muzaffargarh area,Pakistan 
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下载免费PDF全文 The building code of any country is considered to be a basic technical guidance document for the seismic design of structures. However, building codes are typically developed for the whole country, without considering site specific models that incorporate detailed site-specific data. Therefore, the adequacy of the design spectrum for building codes may sometimes be questionable. To study the sufficiency of the building codes of Pakistan (BCP-SP-2007), a deterministic seismic hazard analysis (DSHA) based spectrum was developed for a site in the Muzaffargarh area, Pakistan, using an updated earthquake catalogue, seismic source model, and a next generation attenuation model (NGA-WEST-2). Further, an International Building Code (IBC-2000) spectrum was developed for the study area to compare the results. The DSHA-based response spectrum resulted in a peak ground acceleration (PGA) value of 0.21 g for the Chaudwan fault. The evaluation of BCP-SP-2007 and IBC-2000 spectra provided a critical assessment for analyzing the associated margins. A comparison with the DSHA-based response spectrum showed that the BCP-SP-2007 design spectrum mostly overlapped with the DSHA spectrum unlike IBC-2000. However, special attention is needed for designing buildings in the study area when considering earthquake periods longer than 1 s, and the BCP-SP-2007 spectrum can be enhanced when considering a period range of 0.12–0.64 s. Finally, BCP-SP-2007 is based on a probabilistic approach and its comparison with deterministic results showed the significance of both methods in terms of design. 相似文献