Design energy input spectra for moderate‐seismicity regions

This paper proposes energy input spectra applicable to seismic design of structures located in low‐to‐moderate‐seismicity regions. These spectra represent the load effect, in terms of input energy, of the most severe earthquake that the construction might encounter during its lifetime. The spectra have been derived through dynamic response analyses of over 100 ground motion records obtained from 48 earthquakes that have occurred in Spain. An empirical equation for estimating the energy input contributable to damage from the total input energy is also suggested. This equation takes into account both the damping and the degree of plastification of the structure. Finally, the proposed design energy input spectra are compared with the provisions of the current Spanish Seismic Code and with the response spectra of recent earthquakes that have occurred in Turkey and Taiwan. Copyright © 2002 John Wiley & Sons, Ltd.     

Design energy input spectra for high seismicity regions based on Turkish registers

This work proposes design energy spectra in terms of an equivalent velocity, intended for regions with design peak acceleration 0.3 g or higher. These spectra were derived through linear and nonlinear dynamic analyses on a number of selected Turkish strong ground motion records. In the long and mid period ranges the analyses are linear, given the relative insensitivity of the spectra to structural parameters other than the fundamental period; conversely, in the short period range, the spectra are more sensitive to the structural parameters and, hence, nonlinear analyses are required. The selected records are classified in eight groups with respect to soil type (stiff or soft soil), the severity of the earthquake in terms of surface magnitude $M _\mathrm{s} (M_\mathrm{s} \le $ 5.5 and $M _\mathrm{s} >$ 5.5) and the relevance of the near-source effects (impulsive or vibratory). For each of these groups, median and characteristic spectra are proposed; such levels would respectively correspond to 50 and 95 % percentiles. These spectra have an initial linear growing branch in the short period range, a horizontal branch in the mid period range and a descending branch in the long period range. Empirical criteria for estimating the hysteretic energy from the input energy are suggested. The proposed design spectra are compared with those obtained from other studies.     

Formulation of elastic earthquake input energy spectra

The object of this paper is to introduce a procedure for the determination of elastic design earthquake input energy spectra taking into account the influence of magnitude, soil type and distance from the surface projection of the fault. Firstly, an accurate selection of a large set of representative records has been realized. Secondly, the construction of the design input energy spectra has required determining the spectral shapes and a normalization factor which measures seismic hazard in terms of energy. This factor, denoted as the seismic hazard energy factor, has been defined as the area under the earthquake input energy spectrum in the period interval between 0·05 and 4·0 s. Finally, due to the importance of the source-to-site distance in the evaluation of the input energy, an investigation into the attenuation of the seismic hazard energy factor has been carried out. © 1998 John Wiley & Sons, Ltd.     

地震总输入能量与瞬时输入能量谱的研究

现有的抗震设计理论大多是基于承载力或强度的设计方法,与其相应的反应谱理论最大的缺陷是无法反映地震动持时的影响,而以地震动能量作为设计参数时就能弥补现有抗震理论的不足。本文按照反应谱理论的思路建立了线性单自由度体系的地震动总输入能量谱和瞬时输入能量谱。研究发现,阻尼比为5%时的地震动总输入能量谱和最大瞬时输入能量谱的等价速度谱可以分别用阻尼比为0.5%和10%下的拟速度谱来近似获得;地震波的V/A值大于0.15时,总输入能量谱的Δt谱峰值与地震波的强震持时呈线性增长关系,V/A值小于0.15时,两者间的关系无规律性。最大瞬时输入能量谱的Δt谱峰值基本不受地震波的V/A值与强震持时的影响;输入能量谱(总输入能量谱与最大瞬时输入能量谱)的特征周期随地震波V/A值的增大而增大,根据分析结果本文提出了线性单自由度体系输入能量谱的简化计算方法,方法简便,计算结果偏安全。     

单自由度自复位体系设计能量谱研究

本文对具有旗帜型滞回模型的单自由度自复位体系提出了设计能量谱的构造方法,包括设计输入能量谱和设计滞回耗能比谱。首先按中国规范场地类别选取360条实际强震记录进行时程分析,对影响单自由度自复位体系输入能量谱和滞回耗能比谱的参数,包括地震波类型、滞回模型、阻尼比、延性系数等进行研究。在此基础上分别建议了设计输入能量谱和设计滞回耗能比谱及其曲线参数的确定方法,并与实际强震记录计算结果进行比较。结果表明结构滞回模型对能量谱影响明显;阻尼比和延性系数对输入能量谱的影响在整个周期范围内有显著差异,但均有明显的削峰作用。建议的两种设计能量谱综合考虑了结构参数、地震波参数和中国场地类别的影响,可以较好的拟合实际情况,并对弹塑性单自由度自复位体系在地震作用下的耗能需求做出较准确的估计。     

近断层区的输入能量设计谱及其在基于能量抗震设计中的应用

研究并确定输入能量设计谱是建立基于性能抗震设计和评估能量方法的必要基础。选取断层15km投影距离内的224条强震记录讨论场地类型和断层距等因素的影响,建议了近场地震的输入能量设计谱(EIDS),在与实际记录及日本等国已有抗震规范比较后表明,所建议的设计能量谱能较好地反映近断层区潜在能量需求,在此基础上形成了基于能量的桥梁结构抗震评估设计方法,并用3座实际RC桥墩进行算例验证证明了所建议方法的可行性,表明基于既有抗震规范设计的桥梁结构仍有必要进行考虑近断层效应的耗能能力验算。     

Probabilistic versus deterministic seismic hazard analysis: an integrated approach for siting problems

A methodology is proposed to determine design earthquakes for site-specific studies such as the siting of critical structures (power plants, waste disposals, large dams, etc.), strategic structures (fire stations, military commands, hospitals, etc.), or for seismic microzoning studies, matching the results of probabilistic seismic hazard analyses. This goal is achieved by calculating the source contribution to hazard and the magnitude–distance deaggregation, showing that, varying the selected frequency and the level of hazard, the reference earthquakes are changed as a result. A procedure is then adopted to minimize the residuals between the uniform hazard spectrum (target motion) and the design earthquake spectrum, to provide a specific earthquake scenario encompassing all the frequencies of the target motion. Finally, some considerations on the use and the influence exerted by ground motion uncertainty (σ) on hazard deaggregation are outlined.     

Study on comparison between absolute and relative input energy spectra and effects of ductility factor

Introduction Estimation of an attenuation relationship for strong ground motion parameters has been an interesting research subject in the field of engineering seismology and has played a very important role in seismic safety evaluation, seismic zoning, seismic hazard evaluation of major constructions, etc. At present, the generally used parameters include peak acceleration, peak velocity and elastic response spectrum. Such parameters mentioned above are essentially independent of the duration…     

Estimate of input energy for elasto‐plastic SDOF systems during earthquakes based on discrete wavelet coefficients

The response of an elasto‐plastic single degree of freedom (SDOF) system to ground motion is estimated based on wavelet coefficients calculated by discrete wavelet transform. Wavelet coefficients represent both the time and frequency characteristics of input ground motion, and thus can be considered to be directly related to the dynamic response of a non‐linear system. This relationship between the energy input into an elastic SDOF system and wavelet coefficients is derived based on the assumption that wavelets deliver energy to the structure instantaneously and the quantity of energy is constant regardless of yielding. These assumptions are shown to be valid when the natural period of the system is in the predominant period range of the wavelet, the most common scenario for real structures, through dynamic response analysis of a single wavelet. The wavelet‐based estimation of elastic and plastic energy transferred by earthquake ground motion is thus shown to be in good agreement with the dynamic response analysis when the natural period is in the predominant range of the input. Copyright © 2005 John Wiley & Sons, Ltd.     

An alternative construction of normalized seismic design spectra for near-fault regions

This paper presents a methodology for constructing seismic design spectra in near-fault regions.By analyzing the characteristics of near-fault pulse-type ground motions,an equivalent pulse model is proposed,which can well represent the characteristics of the near-fault forward-directivity and fling-step pulse-type ground motions.The normalized horizontal seismic design spectra for near-fault regions are presented using recorded near-fault pulse-type ground motions and equivalent pulse-type ground motions,which are derived based on the equivalent pulse model coupled with ground motion parameter attenuation relations.The normalized vertical seismic design spectra for near-fault regions are obtained by scaling the corresponding horizontal spectra with the vertical-to-horizontal acceleration spectral ratios of near-fault pulse-type ground motions.The proposed seismic design spectra appear to have relatively small dispersion in a statistical sense.The seismic design spectra for both horizontal and vertical directions can provide alternative spectral shapes for seismic design codes.     

基于公路工程规范地震需求谱研究

从解决桥梁结构的实际问题出发,根据桥梁结构的抗震能力及计力法的需要,由于强度折减系数R与延性系数μ的关系建立弹塑性反应谱的原理,建立了基于《公路工程抗震设计规范》(JTJ 004-89)给出的弹性反应谱的非弹性地震需求谱,为桥梁结构抗震性能评价的研究提供参考意见。     

A preliminary empirical model for frequency-dependent attenuation of Fourier amplitude spectra In Serbia from the Vrancea earthquakes

We present the frequency-dependent attenuation model for Fourier amplitude spectra of strong earthquake ground motion in Serbia from intermediate depth earthquakes in the Vrancea source zone in Romania. The development of this type of scaling is the essential first step toward developing the corresponding attenuation and scaling equations for pseudo relative velocity spectra (PSV), which are necessary for seismic macro- and microzoning in the territory of Serbia. Such scaling is necessary because the Vrancea source zone produces large earthquakes with shaking that attenuates differently from the local earthquakes in Serbia. Development of such a scaling model is associated with several difficulties, the principal one being the lack of recorded strong motion accelerograms at epicentral distances exceeding 300 km. To reduce uncertainties with such scaling, we require our preliminary scaling equations to be consistent with independent estimates of seismic moment, stress drop, and radiated wave energy. In the future, when the recorded strong motion data from Vrancea earthquakes increases several-fold of what it is today, it will become possible to perform this analysis again, thus leading to more reliable and permanent scaling estimates.     

关于抗震设计规范与地震动区划图的有关探讨

本文总结了国内外桥梁抗震设计规范和建筑结构抗震设计规范的设计思想和设计方法,介绍了我国和美国地震动参数区划图的发展和现状,对比分析了抗震规范使用地震区划图的情况。针对我国抗震设计规范和地震动参数区划图的现状,提出了两条建议：（1）地震动参数区划图编制部门应直接提供多水准的地震动参数区划图;（2）抗震设计规范应彻底抛弃设防烈度概念,以地震重现期取代原地震危险程度标示方法。     

Uniform fragility spectra for the performance‐based seismic design of structures considering variabilities in structural properties

This paper presents a new methodology based on structural performance to determine uniform fragility design spectra, i.e., spectra with the same probability of exceedance of a performance level for a given seismic intensity. The design spectra calculated with this methodology provide directly the lateral strength, in terms of yield‐ pseudo‐accelerations, associated with the rate of exceedance of a specific ductility characterizing the performance level for which the structures will be designed. This procedure involves the assessment of the seismic hazard using a large enough number of seismic records of several magnitudes; these records are simulated with an improved empirical Green function method. The statistics of the performance of a single degree of freedom system are obtained using Monte Carlo simulation considering the seismic demand, the fundamental period, and the strength of the structure as uncertain variables. With these results, the conditional probability that a structure exceeds a specific performance level is obtained. The authors consider that the proposed procedure is a significant improvement to others considered in the literature and a useful research tool for the further development of uniform fragility spectra that can be used for the performance‐based seismic design and retrofit of structures.     

Highway bridge seismic design: Summary of FHWA/MCEER project on seismic vulnerability of new highway construction

The Federal Highway Administration (FHWA) sponsored a large, multi-year project conducted by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) titled “Seismic Vulnerability of New Highway Construction” (MCEER Project 112), which was completed in 1998. MCEER coordinated the work of many researchers, who performed studies on the seismic design and vulnerability analysis of highway bridges, tunnels, and retaining structures. Extensive research was conducted to provide revisions and improvements to current design and detailing approaches and national design specifications for highway bridges. The program included both analytical and experimental studies, and addressed seismic hazard exposure and ground motion input for the U.S. highway system; foundation design and soil behavior; structural importance, analysis, and response; structural design issues and details; and structural design criteria. Supported by: the Federal Highway Administration under contract number DTFH61-92-C-00112.     

Probabilistic estimation of maximum inelastic displacement demands for performance‐based design

A probabilistic approach to estimate maximum inelastic displacement demands of single‐degree‐of‐freedom (SDOF) systems is presented. By making use of the probability of exceedance of maximum inelastic displacement demands for given maximum elastic spectral displacement and the mean annual frequency of exceedance of elastic spectral ordinates, a simplified procedure is proposed to estimate mean annual frequencies of exceedance of maximum inelastic displacement demands. Simplifying assumptions are thoroughly examined and discussed. Using readily available elastic seismic hazard curves the procedure can be used to compute maximum inelastic displacement seismic hazard curves and uniform hazard spectra of maximum inelastic displacement demands. The resulting maximum inelastic displacement demand spectra provide a more rational way of establishing seismic demands for new and existing structures when performance‐based approaches are used. The proposed procedure is illustrated for elastoplastic SDOF systems having known‐lateral strength located in a region of high seismicity in California. Copyright © 2007 John Wiley & Sons, Ltd.     

Spectral analysis and design approach for high force‐to‐volume extrusion damper‐based structural energy dissipation

High force‐to‐volume extrusion damping devices can offer significant energy dissipation directly in structural connections and significantly reduce seismic response. Realistic force levels up to 400 kN have been obtained experimentally validating this overall concept. This paper develops spectral‐based design equations for their application. Response spectra analysis for multiple, probabilistically scaled earthquake suites are used to delineate the response reductions due to added extrusion damping. Representative statistics and damping reduction factors are utilized to characterize the modified response in a form suitable for current performance‐based design methods. Multiple equation regression analysis is used to characterize reduction factors in the constant acceleration, constant velocity, and constant displacement regions of the response spectra. With peak device forces of 10% of structural weight, peak damping reduction factors in the constant displacement region of the spectra are approximately 6.5 ×, 4.0 ×, and 2.8 × for the low, medium, and high suites, respectively. At T = 1 s, these values are approximately 3.6 ×, 1.8 ×, and 1.4 ×, respectively. The maximum systematic bias introduced by using empirical equations to approximate damping reduction factors in design analyses is within the range of +10 to ?20%. The seismic demand spectrum approach is shown to be conservative across a majority of the spectrum, except for large added damping between T = 0.8 and 3.5 s, where it slightly underestimates the demand up to a maximum of approximately 10%. Overall, the analysis shows that these devices have significant potential to reduce seismic response and damage at validated prototype device force levels. Copyright © 2007 John Wiley & Sons, Ltd.     

Testing the acceleration spectra given by China and USA seismic codes based on energy supply in near-fault region

For near-fault ground motion,there should be a remarkable impulsive energy supply. Therefore,it is essential to check the validity of actual seismic design codes with energy balance concept. Based on the relationship between the spectrum velocity and the input energy equivalent velocity with 5% damping ratio,the input energy spectra compatible with main China and USA seismic codes were derived,and the accuracy and applicability were veri-fied by using near-fault records. The recommended energy input design spectrum (EIDS) applicable to the distance of 0～15 km from fault was introduced to check the validity of modern seismic codes. Comparison tests show that the GB50011-2001 Code of China can just match the energy effect of near-fault ground motion to a certain extent only under seldom occurred earthquake with fortification intensity of 9 degree for site soil of Ⅲ and IV,indicating that the impact of near-fault effect has not been embodied in the current code acceleration spectrum. In order to make the design spectrum be applicable to near-fault region,it is necessary to adjust the spectrum platform pa-rameters. On the contrary,for distinct fault distance and site soil,the UBC97 Code of USA can match well with the energy supply of near-fault ground motion except for the site soil of hard rock (SA). Accordingly,correctness of the formula derivation in this paper is certified.     

中、美主要抗震设计规范加速度谱的近断层地震动能量检验.

近场地震通常有显著的脉冲型高能输入,有必要从能量角度对现行抗震规范进行有效性检验,以探讨规范加速度设计谱能否体现近断层区域地震地面运动的能量耗散需求. 基于本文作者所建议的5%阻尼比下谱速度与输入能量等效速度之间关系,推导了与当前中、美主要抗震设计规范(GB50011-2001, UBC97)加速度谱相容的输入能量谱,并对其适用范围进行了讨论. 将其与基于实际近断层记录分组所得的输入能量设计谱进行对比表明, 我国GB50011-2001规范除软土场地的9度罕遇烈度外均难以体现近场地震的能量要求,有必要对设计谱平台高度进行调整;而美国UBC97规范则在除SA类场地之外的其它条件下均能较好地与15 km范围内的近场能量需求相吻合,从而也证明了本文推导方法的正确性.      

基于特大地震发生率的川滇地区地震危险性预测新模型

川滇地区是我国地震危险性较高的地区之一.本文基于对特大强震的风险性考虑,使用全球地震模型OpenQuake软件,建立了川滇地区地震危险性预测新模型.首先根据构造特征划分多个震源分区,并整理出这些震源分区内断层活动特征与滑动速率;基于震源分区和断层模型,使用GPS应变率转换成的锥形古登堡-里克特关系作为整个区域的地震积累率,并允许超过历史最大震级的特大地震的出现,结合活动断层滑动速率所积累的地震发生率,给出震源分区内断层地震源和背景地震源的地震发生率的比率分配关系;在活动断层分段上,保留了大型断裂或其主要部分,没有根据小的阶区来对断层进行详细分段,以便分配特大地震发生率;并使用地震率平滑方法分配背景地震发生率.最后在OpenQuake中加入地震动预测方程,计算出了川滇地区的PGA分布图,为区域地震危险性提供科学依据.