Performance-based methodology for assessing seismic vulnerability and capacity of buildings

This paper presents a performance-based methodology for the assessment of seismic vulnerability and capacity of buildings. The vulnerability assessment methodology is based on the HAZUS methodology and the improved capacity- demand-diagram method. The spectral displacement (Sd) of performance points on a capacity curve is used to estimate the damage level of a building. The relationship between Sd and peak ground acceleration (PGA) is established, and then a new vulnerability function is expressed in terms of PGA. Furthermore, the expected value of the seismic capacity index (SCev) is provided to estimate the seismic capacity of buildings based on the probability distribution of damage levels and the corresponding seismic capacity index. The results indicate that the proposed vulnerability methodology is able to assess seismic damage of a large number of building stock directly and quickly following an earthquake. The SCev provides an effective index to measure the seismic capacity of buildings and illustrate the relationship between the seismic capacity of buildings and seismic action. The estimated result is compared with damage surveys of the cities of Dujiangyan and Jiangyou in the M8.0 Wenchuan earthquake, revealing that the methodology is acceptable for seismic risk assessment and decision making. The primary reasons for discrepancies between the estimated results and the damage surveys are discussed.     

四川荣县MS4.7、MS4.3、MS4.9地震房屋震害特征和人员伤亡分析

根据四川荣县M_S4.7、M_S4.3、M_S4.9地震现场灾害调查资料,分析房屋震害特征和人员伤亡情况,结果表明震区房屋破坏类型主要为砖混结构、砖木结构和土木结构,其中砖木结构和土木结构受损比较严重,人员伤亡主要由房屋损坏导致;造成此现象的原因主要是该地区房屋建造年代久远,房屋结构不合理、抗震性能差,短时间地震频发造成震害累积,再加上民众防震减灾意识薄弱等。     

Seismic vulnerability assessment to slight damage based on experimental modal parameters

The aim of this paper is to adjust behaviour models for each class of structure for vulnerability assessment by using ambient vibration. A simple model based on frequencies, mode shapes and damping, taken from ambient vibrations, allows computation of the response of the structures and comparison of inter‐storey drifts with the limits found in the literature for the slight damage grade, considered here as the limit of elastic behaviour. Two complete methodologies for building fragility curves are proposed: (1) using a multi‐degree of freedom system including higher modes and full seismic ground‐motion and (2) using a single‐degree of freedom model considering the fundamental mode f₀ of the structure and ground‐motion displacement response spectra S_D(f₀). These two methods were applied to the city of Grenoble, where 60 buildings were studied. Fragility curves for slight damage were derived for the various masonry and reinforced concrete classes of buildings. A site‐specific earthquake scenario, taking into account local site conditions, was considered, corresponding to an M_L = 5.5 earthquake at a distance of 15 km. The results show the benefits of using experimental models to reduce variability of the slight damage fragility curve. Moreover, by introducing the experimental modal model of the buildings, it is possible to improve seismic risk assessment at an overall scale (the city) or a local scale (the building) for the first damage grade (slight damage). This level of damage, of great interest for moderate seismic‐prone regions, may contribute to the seismic loss assessment. Copyright © 2011 John Wiley & Sons, Ltd.     

Classification of Structure Vulnerability and Evaluation of Earthquake Damage From Future Earthquakes

In this paper,three problems are studied and their results are presented as follows:(1)classification of seismic vulnerability for existing buildings,(2)dynamic earthquake damage matrix analysis method of buildings,and(3)earthquake damage matrix of building in the year 2000.     

Description and analysis of building damage due to Pyrgos, Greece earthquake

On March 1993 an earthquake of magnitude M_s = 5·5 shook Pyrgos, a town in Western Peloponnissos, one of the most seismic prone areas in Greece. The damage induced to modern reinforced concrete buildings was rather light in contrast to the damage induced to historic and traditional buildings of adobe, stone or brick masonry which was severe. In order to study the causes of structural damage, detailed data are collected from a rather large statistical sample of 1023 masonry buildings and 22 reinforced concrete framed buildings with visible damage. For each building the number of storeys, the material of construction, as well as the type and the degree of damage are recorded. In addition, consideration is given to the site of the building within the town and the corresponding soil conditions. For reinforced concrete buildings, damage occured mostly in areas with relatively high estimated spectral accelerations and fundamental soil periods of vibration close to those of the buildings. Nevertheless, further analysis is required to explain the selective damage of a very small number of buildings. For masonry houses, the effect of soil conditions is more systematic. Moreover, the effects of the number of storeys as well as the age and material of construction appear to be dominant.     

Earthquake Damage Scenarios of the Building Stock of Potenza (Southern Italy) Including Site Effects

Damage scenarios relevant to the building stock of the town of Potenza, Southern Italy, are presented. A procedure for the preparation of scenarios has been purposely set up. In the first step, the inventory of the building stock has been made. Location and characteristics of buildings have been obtained from a survey carried out after the 1990 Potenza earthquake and further updated in 1999. In the second step, the absolute vulnerability of the buildings has been evaluated. A hybrid technique has been used, where typological analyses and expert judgement are combined together. Beyond the classes of vulnerability A, B and C of the MSK scale, the class D of EMS98 scale, for the less vulnerable buildings, has been considered. The third step has been the selection of the reference earthquakes by including also local amplification effects. Two events with 50 and 475 years return periods have been chosen as representative, respectively, of a damaging and of a destructive seismic event expected in Potenza. The sites that may exhibit important amplification effects have been identified using the first level method of the TC4 Manual. Damage scenarios of dwelling buildings have been prepared in the fourth step and reported in a GIS. They are relevant to the selected reference earthquakes, taking into account or not site effects. The generally low vulnerability of buildings results in a limited number of damaged buildings for the lower intensity earthquake, and of collapsed buildings, for the higher intensity earthquake. The influence of site effects on the damage distribution is significant. This revised version was published online in July 2006 with corrections to the Cover Date.     

Damage‐dependent vulnerability curves for existing buildings

Seismic behavior of damaged buildings may be expressed as a function of their REsidual Capacity (REC), which is a measure of seismic capacity, reduced by damage. REC can be interpreted as the median value of collapse vulnerability curves. Its variation owing to damage is a useful indication of increased building vulnerability. REC reduction, indicating the lowering of seismic safety after an earthquake (performance loss, PL), represents an effective index for assessing the need of seismic repair/strengthening after earthquakes. The study investigates the applicability of a pushover‐based method in the analysis of damaged structures for the case of existing under‐designed RC buildings. The paper presents a systematization of the procedure in an assessment framework that applies the capacity spectrum method based on inelastic demand spectra; furthermore, the vulnerability variation of a real building is investigated with a detailed case study. The behavior of damaged buildings is simulated with pushover analysis through suitable modification of plastic hinges (in terms of stiffness, strength and residual drift) for damaged elements. The modification of plastic hinges has been calibrated in tests on nonconforming columns. The case study analysis evidenced that, for minor or moderate damages, the original structural displacement capacity was only slightly influenced, but the ductility capacity was significantly reduced (up to 40%) because of the increased structure deformability. This implied performance loss in the range 10%–20%. For severe damages the PL ranged between 41% and 56%. Local mechanism types exhibit PL nearly double with respect to global mechanism types. Copyright © 2012 John Wiley & Sons, Ltd.     

结构易损性分类和未来地震灾害估计

本文研究了下列３个问题：１）对我国现有的建筑进行了易损性分类，并定义了一个区分易损性类别的定理指标；２）建立了未来的建筑震害矩阵与目前现有建筑震者的关系；（３）分析了到２０００年时我国４类易性建筑的震害矩阵。     

无人机摄影技术在精河地震房屋震害定量评估中的应用

利用2017年8月9日精河6.6级地震后获取的高分辨率无人机影像，对叶里斯南也肯村153栋房屋进行结构分类和震害解译，获取研究区内土木结构、砖木结构、砖混结构、框架结构4种类型房屋数量及震害特征，并依据解译结果计算每种结构房屋平均震害指数。由于研究区内砖木结构、砖混结构、框架结构房屋数量偏少，房屋内部的震害难以用无人机影像识别，这3类房屋的震害解译结果与现场调查结果相比差别较大，而土木结构房屋平均震害指数及所对应的地震烈度结果与现场调查结果基本一致，表明无人机影像可为房屋震害定量评估提供重要参考。     

结合天然地震推导水库地震的建筑物易损性

通过类比的方法,选择有现场调查资料并有建筑物破坏比结果的天然地震,基于地震中建筑物震害表现的一致性,以震级、震源深度和极震区烈度为标准,聚类得到与水库地震震害相似的天然地震震例。考虑到宏观经济水平与地震经济损失已有的统计模型,采用了人口密度、人均GDP和三产比例等3个宏观经济指标来反映不同地区的建筑物总体抗震水平,以加权海明(Hamming)距离来定义已知矩阵与目标矩阵的近似度,最终的加权结果即为待求地区的易损性矩阵。通过实际检验,所得的建筑物易损性关系能够反映水库地震的破坏特点,较中强天然地震的易损性要高。这种工作思路也可以用于水库地震其它方面的研究中     

汶川地震中都江堰市的房屋震害

对汶川地震中都江堰市1 005栋房屋的现场震害调查资料进行了统计分析。分析表明,经抗震设计的房屋的震害明显低于未经抗震设计的房屋,前者实现了预期的抗震设防目标;在经抗震设计房屋中,钢筋混凝土框架结构房屋的震害相对较轻,底框架砌体结构房屋和砌体结构房屋次之;中高层建筑和低层建筑的震害比多层建筑轻;学校、医院等公用建筑的损坏与住宅建筑相比较重。     

Characteristics of Seismic Damage of Buildings: Constraints from Tilt Photography Technology

In this paper, the tilt photography data acquisition and three-dimensional modeling of the Tashkurgan M_S5.5 earthquake in Xinjiang are conducted using the tilt photography system of the Rotor UAV. The three-dimensional model is used to interpret the earthquake damage on buildings in the mega-earthquake area in order to acquire different-level house damage in the Kuzirun village disaster area. In addition, the characteristics of seismic damage on typical buildings are analyzed. The results show that the main collapsed houses in the mega-earthquake area are sand-stone buildings, of which about 39% are sand-stone buildings. Several brick-wood buildings and brick-concrete buildings are seriously damaged, while the buildings with frame structures are mainly slightly damaged, and the houses near the macro-epicenter of the earthquake are all in good conditions. Three-dimensional tilt photography technology can vividly display the scene of earthquake disaster, and can provide significant demonstration in building damage degree together with detailed analysis of disaster situation.     

汶川地震中极震区砌体结构教学楼典型震害分析

汶川8.0级大地震造成了巨大的损失,大量学校建筑遭受严重破坏,其中大部分是砌体结构教学楼。在此次地震中,极震区北川县擂鼓镇城区内的初中、小学和幼儿园等砌体结构教学楼的破坏极其严重,结构特征和震害现象十分典型。本文详细地介绍了擂鼓镇城区内5栋砌体结构教学楼的结构构造特点和震害现象特征,同时,总结归纳了砌体结构教学楼的典型震害并分析了震害原因;讨论并分析了建筑含墙率、开间大小、高宽比等因素对建筑的抗震能力的影响;通过结构易损性分析方法对教学楼在不同烈度下的破坏状态进行了计算,并与实际震害进行了对比分析;最后,为灾后教学楼的重建工作提出了建议。     

汶川地震区砖砌体住宅房屋易损性研究

砖砌体住宅房屋占城乡建筑的80%以上,它的易损性分析是进行地震灾害损失预测的重要组成部分。文中介绍了砖砌体住宅房屋易损性的分析方法及存在的问题,充分利用汶川地震区砖砌体住宅房屋的震害调查数据,考虑到建筑物数据的离散性,分别给出了城区砖砌体住宅房屋、农村砖砌体住宅房屋两类建筑物群体的破坏状态易损性曲线包络(最大、平均、最小值),从而给出了其破坏概率矩阵,并给出了每个破坏概率的偏差值。     

Observations of damage due to the Kashmir earthquake of October 8, 2005 and study of current seismic provisions for buildings in Pakistan

On October 8, 2005 an earthquake of magnitude 7.6 (M _w) struck the Kashmir region of Pakistan causing widespread damage to buildings and infrastructure. This paper summarizes field observations of building damage made by the Earthquake Engineering Field Investigation Team (EEFIT) after the event, where the performance of residential, commercial and government buildings was investigated. A study of the seismic design provisions currently in place in Pakistan is presented and compared with seismic provisions of EC8 (1998) and UBC (1997). Several problems are identified for the implementation of the Pakistan seismic code in its current form and recommendations are made for its improvement in order to be used for the reconstruction of affected areas.     

基于新视角的震害分析——以四川长宁6.0级地震为例

四川长宁6.0级地震发生后，作者第一时间前往地震现场，获得第一手震害资料。基于“散、脆、偏、单”评估法，对当地建筑物震害特点和成灾机理进行深入剖析，并提出整治措施。实际震害显示，当前我国城乡建筑亟待解决的问题是“散”和“脆”；学校建筑和底商结构在此次地震中仍表现出诸多抗震不利问题，集中体现在因填充墙布置不合理导致的“偏”；高层建筑主体结构虽在地震后保存完好，但填充墙破坏较重，修缮费用较高。震害调查结果警醒行业人员需围绕实际震害特点精准发力，优化结构概念设计，全面提升抗震能力，推动韧性城乡建设。     

广西靖西Ms5.2级地震房屋破坏特征

近年来广西地震发生频率明显提高,陆续发生了3次5级以上中强地震,包括2016年苍梧5.4级地震、2019年北流5.2级地震和2019年靖西5.2级地震,这可能意味着广西地区进入了地震活跃期。2019年靖西5.2级地震造成较重的房屋建筑物破坏,是分析广西房屋震害很好的样本。本文对各烈度区内不同结构类型房屋的震害现象进行了整理和统计,分析了不同结构类型房屋的震害特征与震害原因。结果显示:简易房屋除年久失修的之外基本完好;砌体结构房屋因结构不规则,缺乏抗震构造措施等,破坏较重,且破坏形式多样;框架结构房屋主体完好但填充墙会出现破坏。     

Analysis of damage data of low-rise buildings subjected to a shallow Mw6.3 earthquake

In May 2008 a shallow M_w6.3 earthquake struck South Iceland with an epicentre close to two small towns. Nearly 5000 low-rise residential buildings were affected. The recorded maximum PGA was 0.88 g. A great deal of damage occurred, but there was no loss of life. In Iceland all buildings are registered in a detailed official database and insurance against natural disasters is obligatory. As the repair costs for every affected building had to be assessed for insurance purposes this provided an unusual opportunity to review structural performance across the whole population of buildings in the affected area. The estimated repair cost was classified in a number of subcategories covering structural and non-structural damage for five different residential building typologies. Study of these buildings showed that non-structural damage dominated the overall damage. The main monetary damage was cosmetic damage of partition walls and flooring. The structural systems performed quite well and no buildings collapsed.     

Seismic response estimation method for earthquake‐damaged RC buildings

This study proposes a procedure for identifying spectral response curves for earthquake‐damaged areas in developing countries without seismic records. An earthquake‐damaged reinforced concrete building located in Padang, Indonesia was selected to illustrate the identification of the maximum seismic response during the 2009 West Sumatra earthquake. This paper summarizes the damage incurred by the building; the majority of the damage was observed in the third story in the span direction. The damage was quantitatively evaluated using the damage index R according to the Japanese guidelines for post‐earthquake damage evaluation. The damage index was also applied to the proposed spectral response identification method. The seismic performance of the building was evaluated by a nonlinear static analysis. The analytical results reproduced a drift concentration in the third story. The R‐index decreased with an increase in the story drift, which provided an estimation of the maximum response of the building during the earthquake. The estimation was verified via an earthquake response analysis of the building using ground acceleration data, which were simulated based on acceleration records of engineering bedrock that considered site amplification. The maximum response estimated by the R‐index was consistent with the maximum response obtained from the earthquake response analysis. Therefore, the proposed method enables the construction of spectral response curves by integrating the identification results for the maximum responses in a number of earthquake‐damaged buildings despite a lack of seismic records. Copyright © 2016 The Authors. Earthquake Engineering & Structural Dynamics published by John Wiley & Sons Ltd.     

基于无人机影像的九寨沟地震建筑物震害定量评估

利用2017年8月8日九寨沟7.0级地震震后获取的无人机影像,结合地面震害调查资料,分析各类建筑物震害特征,建立建筑物震害无人机遥感解译标志;选取地震灾区漳扎镇(部分区域)和荷叶寨2个区域作为研究区,进行了无人机遥感建筑物震害提取,基于遥感震害指数进行了震害定量评估,并与现场建筑物震害调查统计结果进行了比较验证。结果显示,遥感解译建筑物震害与实际震害程度相吻合,表明利用震后快速获取的高分辨率无人机影像,可以较为准确地识别建筑物震害,进而为地震灾害定量评估和应急救援辅助决策提供重要参考。