从砌体的震害看抗震设计观念中存在的问题

以云南省破坏性地震中砌体结构房屋的典型震害实例,分析、总结了影响砌体结构抗震性能的措施和经验。针对按现行抗震规范设防后仍要遭受巨大经济损失这一事实,作试图从抗震设计规范的基本理念上分析引起破坏的原因,从而指出研究结构性能设计理论的必要性。     

A RATE-DEPENDENT ISOTROPIC DAMAGE MODEL FOR THE SEISMIC ANALYSIS OF CONCRETE DAMS

In this paper a rate-dependent isotropic damage model developed for the numerical analysis of concrete dams subjected to seismic excitation is presented. The model is shown to incorporate two features essential for seismic analysis: stiffness degradation and stiffness recovery upon load reversals and strain-rate sensitivity. The issue of mesh objectivity is addressed using the concept of the ‘characteristic length’ of the fracture zone, to show that both the softening modulus and the fluidity parameter must depend on it to provide consistent results as the computational mesh is refined. Some aspects of the numerical implementation of the model are also treated, to show that the model can be easily incorporated in any standard non-linear finite element code. The application of the proposed model to the seismic analysis of a large gravity concrete dam shows that the structural response may vary significantly in terms of the development of damage. The inclusion of rate sensitivity is able to reproduce the experimental observation that the tensile peak strength of concrete can be increased up to 50 percent for the range of strain rates that appear in a structural safety analysis of a dam subjected to severe seismic actions.     

建筑物震害直接经济损失评定的误差分析

本文概述了引起震害损失评定误差的主要因素。通过实际震害评定资料，定量分析了震害损失评估中各因素形成误差数值的大小。采用以采样平均相对误差或采样均方误差及损失值相对误差来评估震害评定质量的方法，并通过分析给出综合衡量评定精度的量化指标，对震害经济损失评定准确度进行评估。     

矩形钢筋混凝土蓄水池震害预测方法及分析程序简介

本给出了一种矩形有疬钢筋混凝土蓄水池的震害预测方法和计算分析程序，并对两蓄水池进行了震害预测分析，得出震害经验相符合的结论－地下式水池比地上水池的抗震能力强，从而证明了本方法的实用性。     

2013年西藏左贡与芒康交界6.1级地震的房屋震害特征

2013年8月12日在西藏自治区左贡与芒康交界发生6.1级地震,该地震宏观震中位于左贡县田妥镇嘎益村-仁果乡吞永村一带,最大烈度Ⅷ度,但不构成Ⅷ度区.根据现场工作队所收集的资料,分析了震区各类房屋建筑的震害特征及其破坏原因,并根据此次地震对该地区房屋所造成的破坏程度提出了防震减灾研究建议,并强调了此类民居需要加强抗震设计.     

超高层建筑设计地震动参数的研究

本文以沈阳市世纪华丰文化广场工程场地为例,在地震危险性分析的基础上,进行土层地震反应分析,对超高层建筑设计地震动参数的确定进行研究,为抗震设计提供可靠依据。     

STUDY ON THE MRF-BASED METHOD FOR DAMAGED BUILDINGS EXTRACTION FROM THE SINGLE-PHASE SEISMIC IMAGE

Earthquake events are one of the most extraordinarily serious natural calamities, which not only cause heavy casualties and economic losses, but also various secondary disasters. Such events are devastating, and have far-reaching influences. As the main disaster bearing body in earthquake, buildings are often seriously damaged, thus it can be used as an important reference for earthquake damage assessment. Identifying damaged buildings from post-earthquake images quickly and accurately is of real importance, which has guidance meaning to rescue and emergency response. At present, the assessment of earthquake damage is mainly through artificial field investigation, which is time-consuming and cannot meet the urgent requirements of rapid emergency response. Markov Random Field(MRF)combines the neighborhood system of pixels with the prior distribution model to effectively describe the dependence between spatial pixels and pixels, so as to obtain more accurate segmentation results. The support vector machine(SVM)model is a simple and clear mathematical model which has a solid theoretical basis; in addition, it also has unique advantages in solving small sample, nonlinear and high-dimensional pattern recognition problems. Thus, in this paper, a Markov random field-based method for damaged buildings extraction from the single-phase seismic image is proposed. The framework of the proposed method has three components. Firstly, Markov Random Field was used to segment the image; then, the spectral and texture features of the post-earthquake damaged building area are extracted. After that, Support Vector Machine was used to extract the damaged buildings according to the extracted features. In order to evaluate the proposed method, 5 areas in ADS40 earthquake remote sensing image were selected as experimental data, this image covers parts of Wenchuan City, Sichuan Province, where an earthquake had struck in 2008. And in order to verify the applicability of this method to different resolution images, an experimental area was selected from different resolution images obtained by the same equipment. The experimental results show that the proposed method has good performance and could effectively identify the damaged buildings after the earthquake. The average overall accuracy of the selected experimental areas is 93.02%. Compared with the result extracted by the widely used eCognition software, the proposed method is simpler in operation and can improve the extraction accuracy and running time significantly. Therefore, it has significant meaning for both emergency rescue work and accurate disaster information providing after earthquake.     

AN ANALYSIS OF THE SEISMIC CHARACTERISTICS OF STEEL-JACKETED CIRCULAR BRIDGE COLUMNS

The current approach for seismic retrofit of deficient bridge columns in California involves extensive use of steel jacketing. In this paper, the influence of steel jacketing on the lateral response of circular bridge columns is studied; particularly, the enhancement of the ultimate compressive strain of concrete, the increase in curvature ductility capacity and the increase in lateral stiffness are investigated. The current steel jacket thickness used in California is shown to enhance the ultimate compressive strain of concrete by 4–9 times the spalling strain of unconfined concrete. For larger steel jacket thickness, the ultimate limit state of steel-jacketed columns may be governed by the low-cycle fatigue fracture of the longitudinal reinforcement instead of the ultimate compressive strain of concrete. Steel jacketing is also expected to increase significantly the lateral stiffness of columns if full-height steel jackets are used. The increase in lateral stiffness of flexural columns (3⩽L/D⩽9) is estimated to be 35–60 per cent using current jacket thickness. Inelastic dynamic analyses of steel-jacketed columns using ground motions recorded during the 1989 Loma Prieta earthquake indicated that the current steel jacket thickness provides adequate protection against the damage potential of the ground motions with comparable spectral acceleration as that specified in current design spectra, and the damage sustained by the steel-jacketed column is likely to be repairable.     

辽西地震重点监视区桥梁震害预测

采用统计回归方法，对辽西地震重点监视防御区内４条国家级公路的桥梁１３３座、４次国有铁路的桥梁３３１座，以桥梁震害等级划分原则，求取其震害指数、判定震害等级。     

山东潍坊地区多层砖房震害预测

利用多层砌体房屋震害预测专家系统,对山东潍坊地区１８２栋多层砖房逐栋进行了单体房屋的震害预测,在此基础上,统计分析了该地区多层砖房的地震易损性特征,并进行了初步震害预测研究,给出了该类房屋的易损性矩阵,各破坏等级的损失参数矩阵和对应不同地震烈度的相对损失预测,为进一步开展震害预测和采取地对性的防震减灾对策提供了科学依据。     

江苏省农村民居集中住宅区房屋抗震性能探讨

本文通过对常熟市、扬州市、姜堰市部分村镇的农村民居集中住宅区房屋建设进行调查和分析,阐述了江苏省农村民居集中住宅区房屋抗震性能的新型结构类型、斜坡屋面结构、内部结构等典型问题,探讨了改善农村民居集中住宅区房屋抗震性能的政策保证、技术支持、资金来源以及其他方面的途径和建议,对农村民居集中住宅区防震减灾及抗震实用化技术的研究与开发具有重要应用价值,为农村民居集中住宅区建设中改善房屋抗震性能提供参考和依据。     

黄土生土建筑震害预测研究

通过对黄土地区生土建筑民房的现场调查和测试，分析了各种类型生土建筑的结构特点和自振特性，归纳总结了影响生土建筑震害的主要因素和目前存在的主要问题，在此基础上提出了生土建筑震害预测方法，并给出了初步预测结果。     

A METHOD OF ESTIMATING THE PARAMETERS OF TUNED MASS DAMPERS FOR SEISMIC APPLICATIONS

The optimum parameters of tuned mass dampers (TMD) that result in considerable reduction in the response of structures to seismic loading are presented. The criterion used to obtain the optimum parameters is to select, for a given mass ratio, the frequency (tuning) and damping ratios that would result in equal and large modal damping in the first two modes of vibration. The parameters are used to compute the response of several single and multi-degree-of-freedom structures with TMDs to different earthquake excitations. The results indicate that the use of the proposed parameters reduces the displacement and acceleration responses significantly. The method can also be used in vibration control of tall buildings using the so-called ‘mega-substructure configuration’, where substructures serve as vibration absorbers for the main structure. It is shown that by selecting the optimum TMD parameters as proposed in this paper, significant reduction in the response of tall buildings can be achieved. © 1997 John Wiley & Sons, Ltd.     

On the evaluation of seismic response of structures by nonlinear static methods

In the most recent seismic codes, the assessment of the seismic response of structures may be carried out by comparing the displacement capacity, provided by nonlinear static analysis, with the displacement demand. In many cases the code approach is based on the N2 method proposed by Fajfar, which evaluates the displacement demand by defining, as an intermediate step, a single degree‐of‐freedom (SDOF) system equivalent to the examined structure. Other codes suggest simpler approaches, which do not require equivalent SDOF systems, but they give slightly different estimation of the seismic displacement demand. The paper points out the differences between the methods and suggests an operative approach that provides the same accuracy as the N2 method without requiring the evaluation of an equivalent SDOF system. A wide parametric investigation allows an accurate comparison of the different methods and demonstrates the effectiveness of the proposed operative approach. Copyright © 2009 John Wiley & Sons, Ltd.     

改进的钢筋混凝土结构双参数地震破坏模型

本文在分析现有结构地震破坏模型的基础下，提出了一种改进掇参数地震破坏模型。文中采用三线退化型恢复力模型对实际钢筋混凝土结构在实际地震作用下的变形与累积耗能，极限变形与极限滞回耗能进行了分析，通过模型计算的破损结果与实际在结果的对比，研究了模型参数，从而建立了钢筋混凝土结构的双参数地震破坏模型。     

Estimation of inelastic deformation demands in multistorey RC frame buildings

Estimation of peak inelastic deformation demands is a key component of any displacement-based procedure for earthquake-resistant design of new structures or for seismic evaluation of existing structures. On the basis of the results of over a thousand non-linear dynamic analyses, rules are developed for the estimation of mean and upper-characteristic peak inelastic interstorey drifts and member chord rotations in multistorey RC frame buildings, either bare or infilled in all storeys but the first. For bare frame structures, mean inelastic deformation demands can be estimated from a linear, equivalent static, or preferably multimodal response spectrum analysis with 5 per cent damping and with the RC members considered with their secant stiffness at yielding. 95 per cent characteristic values can be estimated as multiples of the mean deformations. For open-first-storey buildings, the linear analysis can be equivalent static, with the infills modelled as rigid bidiagonal struts and all RC members considered with their secant stiffness to yielding. Copyright © 1999 John Wiley & Sons, Ltd.     

NUMBER OF MODES FOR THE SEISMIC DESIGN OF BUILDINGS

The effect of higher modes on the maximum response of buildings subjected to one horizontal component of earthquake ground motion is discussed with the objective of developing better design formulas for use in building design. Ideal buildings of different numbers of storeys and structural systems are defined; their dynamic properties that define higher mode contribution are identified and are shown to be representative of real buildings. Design formulas that give the required number of modes to be used in a dynamic analysis are developed from parametric studies as a function of the admissible error, the number of storeys and the relation between the fundamental period and the corner spectrum period. The recommendations are simple to use and more rational and accurate than the ones actually in use in most seismic design codes.     

SIMPLE PUSH-OVER ANALYSIS OF ASYMMETRIC BUILDINGS

A simple method for the non-linear static analysis of complex building structures subjected to monotonically increasing horizontal loading (push-over analysis) is presented. The method is designed to be a part of new methodologies for the seismic design and evaluation of structures. It is based on the extension of a pseudo-three-dimensional mathematical model of a building structure into the non-linear range. The structure consists of planar macroelements. For each planar macroelement, a simple bilinear or multilinear base shear–top displacement relationship is assumed. By a step-by-step analysis an approximate relationship between the global base shear and top displacement is computed. During the analysis the development of plastic hinges throughout the building can be monitored. The method has been implemented into a prototype computer program. In the paper the mathematical model, the base shear–top displacement relationships for different types of macroelements, and the step-by-step computational procedure are described. The method has been applied for the analysis of a symmetric and an asymmetric variant of a seven-storey reinforced concrete frame–wall building, as well as for the analysis of a complex asymmetric 21-storey reinforced concrete wall building. The influence of torsion on structural behaviour is discussed. © 1997 by John Wiley & Sons, Ltd.     

EFFECT OF MODELLING ASSUMPTIONS AND INPUT MOTION CHARACTERISTICS ON SEISMIC DESIGN PARAMETERS OF RC BRIDGE PIERS

Modelling assumptions, boundary and loading conditions have a significant effect on analytical assessment of ductility supply and demand measures for RC bridges, a structural form which had suffered extensively in recent earthquakes. In recognition of the important role played by analysis in advancing seismic design of bridges, this paper is concerned with assessing the effect of model characteristics and earthquake strong-motion selection on analytical action and deformation seismic design parameters. This is of particular significance when viewed in the light of the large capital investment and problems with the satisfaction of dynamic similitude encountered in physical testing of piers and pier-deck assemblies. The models studied range between simple fixed-base cantilever and inclusion of both soil and deck effects, represented by assemblies of springs in translational and rotational degrees of freedom. Moreover, two sets of earthquake records are used in dynamic analysis, each comprising six records covering low, intermediate and high a/v, where a and v are the peak ground acceleration and velocity, respectively. The two sets differ in the scaling procedure employed to bring them to a common level of severity; the first set is obtained by direct acceleration scaling whilst the second utilizes the concept of velocity spectral intensity. The results from static and dynamic analysis, using advanced material characterization and solution procedures, are assessed and discussed. Subject to the limitations of the study, outlined in the paper, the results indicate that the inclusion of deck stiffness and/or soil representation is essential to avail of accurate seismic response parameters. However, the effect of variations in soil stiffness and/or deck torsional rigidity applied in the analysis is rather small, compared to the inclusion/exclusion of the model feature. Moreover, it is also observed that using acceleration scaling leads to much larger scatter in the results than when velocity spectral intensity scaling is used. Finally, the results from two particular earthquakes, Friuli and El Centro, highlight the peril of using a small number of records selected without due consideration to the relationship between their wave form, predominant periods and spectral shapes on the one hand and the response periods of the structure on the other.     

新疆巴楚-伽师6.8级地震房屋建筑震害原因浅析

介绍了巴楚—伽师6．8级地震灾区的主要房屋建筑结构类型以及地震中房屋的震害现象和破坏特点，分析了引起房屋破坏的原因，总结了房屋建筑抗震工作中的经验与教训。