Development of damage probability matrices based on Greek earthquake damage data

A comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The observational database was obtained from post-earthquake surveys carried out in the area struck by the September 7, 1999 Athens earthquake. After analysis of the collected observational data, a unified damage database has been created which comprises 180,945 damaged buildings from/after the near-field area of the earthquake. The damaged buildings are classified in specific structural types, according to the materials, seismic codes and construction techniques in Southern Europe. The seismic demand is described in terms of both the regional macroseismic intensity and the ratio αg/ao, where αg is the maximum peak ground acceleration (PGA) of the earthquake event and ao is the unique value PGA that characterizes each municipality shown on the Greek hazard map. The relative and cumulative frequencies of the different damage states for each structural type and each intensity level are computed in terms of damage ratio. Damage probability matrices (DPMs) and vulnerability curves are obtained for specific structural types. A comparison analysis is fulfilled between the produced and the existing vulnerability models.     

Empirical seismic vulnerability analysis for masonry buildings based on school buildings survey in Iran

School facilities in Iran, in particular masonry schools, have shown poor performance during past earthquakes and can be identified as one of the parts of the country’s infrastructure that is most vulnerable to earthquakes. Hence, in this paper a method to perform index-based damage assessment for brick masonry schools located in the province of Yazd, the central region of Iran, using a comprehensive database of school buildings, is proposed. The database was obtained from the field survey forms applied for each observed school to collect the features of and damage to the structure. The results of a vulnerability index method developed in Iran are employed as input data to obtain empirical fragility curves for the school inventory. The Macroseismic model and GNDT II level method are two empirical methods combined in this procedure. Finally, the procedure is verified using damage survey data obtained after recent earthquakes (1990 Manjil–Rudbar earthquake and 2003 Bam earthquake) that occurred in Iran.     

Vulnerability and risk analysis of monuments in Málaga city’s historical centre (Southern Spain)

A vulnerability analysis of some historical and monumental buildings in the city of Málaga is presented in this paper. More than twenty of these monuments were severely damaged or completely destroyed due to the large earthquake (I _max = VIII–IX) occurred in the Málaga region in October 1680. The vulnerability index methodology has been used in this paper. This technique is based on statistical data from seismic damage caused to Italian monuments for the past 30?years. For each building, vulnerability curves have been obtained and damage grades have been estimated. A comparison has been carried out between the expected damage grades and the damage observed from past earthquakes, in order to check the feasibility of applying this methodology to Spanish monuments. This comparison has been possible due to the fact that detailed seismic damage information exists for monuments in the city of Málaga that still exist today, which is a very uncommon case in Spain. Results show a good consistency between expected and observed damage, especially for the churches type. Two seismic scenarios have been proposed for the city centre, one deterministic and one probabilistic, where 54 historical and modern buildings have been analyzed. Both scenarios show worrying results, especially for the types of churches, chapels and towers, where expected high probabilities of suffering very heavy damage or even collapse have been obtained. It is highly recommended to take the necessary measures, in the hope of trying to avoid the possible damage that can be expected from future earthquakes.     

Seismic vulnerability and risk evaluation for old urban nuclei

The evaluation of the seismic damageability of existing buildings is a primary element in the planning for mitigation of earthquake effects. To this purpose, the use of the vulnerability index has been recently proposed and adopted in various surveys in Italy. The index results from grading the status of various structural and non-structural components exposed to damage in a seismic event. The effectiveness of the vulnerability index as a measure of the health status of buildings is discussed on the basis of regional surveys of vulnerability index versus reported damage, carried out in various Italian areas such as Friuli and the city of Gubbio. Also, investigation of the items most effective in describing damageability among those contributing to the index is performed, in view of formulating a reduced survey procedure. A damage versus vulnerability index database collected in these surveys is presented as well. Finally, a vulnerability index based procedure to evaluate the expected damage in a territory is proposed.     

Observational fragility functions for residential stone masonry buildings in Nepal

This paper outlines the seismic vulnerability of rural stone masonry buildings affected by the 2015 Gorkha earthquake sequence. Summary of field observation is presented first and empirical fragility curves are developed from the detailed damage assessment data from 603 villages in central, eastern and western Nepal. Fragility curves are developed on the basis of 665,515 building damage cases collected during the post-earthquake detailed damage assessment campaign conducted by Government of Nepal. Two sets of fragility functions are derived using peak ground acceleration and spectral acceleration at 0.3 s as the intensity measures. The sum of the results highlights that stone masonry buildings in Nepal are highly vulnerable even in the case of low to moderate ground shaking. The results further indicate that in the case of strong to major earthquakes, most of the stone masonry buildings in Nepal would sustain severe damage or collapse.     

基于时变地震损伤模型的多龄期钢框架结构易损性分析

基于时变地震损伤模型提出酸性大气环境作用下多龄期钢框架结构概率地震易损性分析的方法及步骤;考虑服役龄期对钢框架结构抗震性能的影响,分别建立时变概率地震需求模型、时变概率抗震能力模型及时变易损性模型;在概率地震需求分析及概率抗震能力分析的基础上,得到多龄期(20年、30年、40年、50年)钢框架结构的易损性模型及易损性曲线。     

A hybrid method for the vulnerability assessment of R/C and URM buildings

The methodology followed by the Aristotle University (AUTh) team for the vulnerability assessment of reinforced concrete (R/C) and unreinforced masonry (URM) structures is presented. The paper focuses on the derivation of vulnerability (fragility) curves in terms of peak ground acceleration (PGA), as well as spectral displacement (s _d), and also includes the estimation of capacity curves, for several R/C and URM building types. The vulnerability assessment methodology is based on the hybrid approach developed at AUTh, which combines statistical data with appropriately processed (utilising repair cost models) results from nonlinear dynamic or static analyses, that permit extrapolation of statistical data to PGA’s and/or spectral displacements for which no data are available. The statistical data used herein are from earthquake-damaged greek buildings. An extensive numerical study is carried out, wherein a large number of building types (representing most of the common typologies in S. Europe) are modelled and analysed. Vulnerability curves for several damage states are then derived using the aforementioned hybrid approach. These curves are subsequently used in combination with the mean spectrum of the Microzonation study of Thessaloniki as the basis for the derivation of new vulnerability curves involving spectral quantities. Pushover curves are derived for all building types, then reduced to standard capacity curves, and can easily be used together with the S _d fragility curves as an alternative for developing seismic risk scenarios.     

Sand blows as a potential tool for magnitude estimation of pre-instrumental earthquakes

A worldwide database of liquefaction-induced sand blows has been compiled to generate empirical relationships between earthquake parameters and sand blow geometries. Curves resulting from these empirical relationships can be used afterwards for the study of historic and pre-historic earthquakes that formed sand blows. This database only incorporates instrumental earthquakes inducing sand blows, characterised in terms of magnitude (Mw), hypocentral location and focal mechanism solution. Two relationships are herein presented. The first curve, minimum likelihood of liquefaction occurrence (magnitude/epicentral distance), displays a logarithmic behaviour, as others already proposed. The second curve of sand-blow diameter vs epicentral distance is the first proposal of this kind, whose shape follows a negative power-law. Magnitude estimations of (pre-)historic earthquakes then may be attempted through these empirical relationships. Resulting magnitudes derived from these curves should be mostly considered as underestimated. The curves will reflect actual magnitudes only if, correspondingly, the farthest and largest blow has ever been reported during the after-earthquake survey. Following the same principle, a magnitude estimation resulting from the measuring of a sand blow can only be considered as minimal because it is almost impossible to ascertain that the measured feature is the biggest one produced by the earthquake under evaluation. Finally, these results call for thorough surveys of induced effects after every future moderate-to-large earthquake, as any empirical relationship simply improves by incorporating new data.     

Building vulnerability assessment and damage scenarios in Celano (Italy) using a quick survey data-based methodology

A procedure for assessing the seismic vulnerability of residential buildings is presented along with the results of its application in an Italian town in Abruzzo (Celano Aq). This procedure is part of a methodological proposal which includes specific studies on expected seismic inputs and site effects analyses. The procedure is based on a simplified collection of data, such as typological features and factors concerning the seismic behaviour of buildings, and provides an estimate of seismic vulnerability and an expected damage forecast using fragility curves. The instruments and methods used for the Celano project are an updated and improved version of those applied to previous vulnerability investigations. This paper demonstrates how this procedure can meet the objectives of the integrated methodology proposed. In fact, the information that can be obtained using this procedure—state of vulnerability, risk analyses and GIS presentations of damage scenarios—could be used in urban planning to reduce seismical risk.     

基于地震动参数的建筑物震害预测

针对目前我国流行的基于地震烈度的震害预测方法中的不足,本文借助美国广泛使用的地震损失评估软件HAZUS99技术手册中房屋易损性评估方法的表达形式,结合我国的震害经验,提出了一套基于地震动参数的群体建筑物震害预测方法。依据易损性矩阵,采用遗传算法与单纯形法相结合的混合算法反演典型结构的抗力曲线和易损性曲线的参数。给定表示地震作用的需求谱,就可以方便地完成典型结构的震害预测。以两个地区的多层砌体房屋为例,说明了本文提出方法的具体步骤,诊证了可靠性。     

Processing Italian damage data to derive typological fragility curves

Typological fragility curves have been derived from post-earthquake survey data on building damage, collected in the areas affected by the most relevant Italian earthquakes of the last three decades. A complex and time consuming codification and reinterpretation work has been done on a set of about 150,000 survey building records, in order to define empirical damage probability matrices for several building typologies, characteristic of the Italian building stock. The obtained data have then been processed by advanced nonlinear regression methods in order to derive typological fragility curves. These curves, organised in five damage levels, provide useful information both for relative comparisons among typologies and for seismic risk analyses at different scales. By combining hazard definitions, fragility curves and inventory data, complete earthquake risk scenario studies can be performed, but even the single convolution of hazard and fragility allows to obtain typological risk maps, both for single damage state definitions and for concise average loss parameters. The very high potential of these results is shown by some applications reported in the paper.     

地震波斜入射输入体系下坝后式厂房易损性分析

为了考虑地震波斜入射对坝后式厂房易损性的影响,通过斜入射SV波和P波波场叠加,在地表得到与实测地震动一致的设计地震动分量。同时为了考虑坝后式厂房的动力损伤,在程序中嵌入混凝土动力损伤本构,编写了可以考虑地震波斜入射体系的结构易损性分析程序。最后从太平洋地震工程研究中心（PEER）数据库中选取26条近场地震动数据,根据峰值地面加速度（PGA）对每条地震波进行调幅,以我国西南地区某坝后式厂房为工程实例,用增量动力学分析法计算了其上下游墙体在不同强度斜入射体系地震动作用下的易损性曲线。与传统垂直入射模式下的地震易损性曲线对比发现,传统垂直入射下的破坏概率较高,两种入射模式破坏概率最大相差26%。其中,坝后式厂房下游墙的破坏概率比上游墙大,最大相差可19%。因此坝后式厂房的抗震设计需考虑地震波斜入射的影响,并重点考虑下游墙部位的抗震安全性。     

Effect of earthquake ground motions on fragility curves of highway bridge piers based on numerical simulation

Fragility curves express the probability of structural damage due to earthquakes as a function of ground motion indices, e.g., PGA, PGV. Based on the actual damage data of highway bridges from the 1995 Hyogoken‐Nanbu (Kobe) earthquake, a set of empirical fragility curves was constructed. However, the type of structure, structural performance (static and dynamic) and variation of input ground motion were not considered to construct the empirical fragility curves. In this study, an analytical approach was adopted to construct fragility curves for highway bridge piers of specific bridges. A typical bridge structure was considered and its piers were designed according to the seismic design codes in Japan. Using the strong motion records from Japan and the United States, non‐linear dynamic response analyses were performed, and the damage indices for the bridge piers were obtained. Using the damage indices and ground motion indices, fragility curves for the bridge piers were constructed assuming a lognormal distribution. The analytical fragility curves were compared with the empirical ones. The proposed approach may be used in constructing the fragility curves for highway bridge structures. Copyright © 2001 John Wiley & Sons, Ltd.     

Models for reproducing the damage scenario of the Lorca earthquake

A damage scenario modelling is developed and compared with the damage distribution observed after the 2011 Lorca earthquake. The strong ground motion models considered include five modern ground motion prediction equations (GMPEs) amply used worldwide. Capacity and fragility curves from the Risk-UE project are utilized to model building vulnerability and expected damage. Damage estimates resulting from different combinations of GMPE and capacity/fragility curves are compared with the actual damage scenario, establishing the combination that best explains the observed damage distribution. In addition, some recommendations are proposed, including correction factors in fragility curves in order to reproduce in a better way the observed damage in masonry and reinforce concrete buildings. The lessons learned would contribute to improve the simulation of expected damages due to future earthquakes in Lorca or other regions in Spain with similar characteristics regarding attenuation and vulnerability.     

Empirical seismic fragility for the precast RC industrial buildings damaged by the 2012 Emilia (Italy) earthquakes

The paper analyses the seismic fragility of precast reinforced concrete buildings using observational damage data gathered after the 2012 Emilia earthquakes that struck Northern Italy. The damage level in 1890 buildings was collected, classified and examined. Damage matrices were then evaluated, and finally, empirical fragility curves were fitted using Bayesian regression. Building damage was classified using a six‐level scale derived from EMS‐98. The completeness of the database and the spatial distribution of the buildings investigated were analysed using cadastral data as a reference. The intensity of the ground motion was quantified by the maximum horizontal peak ground acceleration, which was obtained from ShakeMaps. Copyright © 2017 John Wiley & Sons, Ltd.     

Empirical seismic vulnerability assessment of Icelandic buildings affected by the 2000 sequence of earthquakes

In June 2000, two Mw6.5 earthquakes occurred within a 4-day interval in the largest agricultural region of Iceland causing substantial damage and no loss of life. The distance between the earthquake epicentres and the fault rupture was approximately 15 km. Nearly 5000 low-rise residential buildings were affected, some of which were located between the faults and exposed to strong ground motion from both events. The post-earthquakes damage and repair costs for every residential building in the epicentral region were assessed for insurance purposes. The database is detailed and complete for the whole region and represents one of the best quality post-earthquake vulnerability datasets used for seismic loss estimation. Nonetheless, the construction of vulnerability curves from this database is hampered by the fact that the loss values represent the cumulative damage from two sequential earthquakes in some areas, and single earthquakes in others. A novel methodology based on beta regression is proposed here in order to define the geographical limits on areas where buildings sustained cumulative damage and predict the seismic losses for future sequence of events in each area. The results show that the average building loss in areas affected by a single event is below 10% of the building replacement value, whilst this increases to an average of 25% in areas affected by the two earthquakes. The proposed methodology can be used to empirically assess the vulnerability in other areas which experienced sequence of events such as Emilia-Romagna (Italy) in 2012.     

Statistical procedures for developing earthquake damage fragility curves

This paper describes statistical procedures for developing earthquake damage fragility functions. Although fragility curves abound in earthquake engineering and risk assessment literature, the focus has generally been on the methods for obtaining the damage data (i.e., the analysis of structures), and little emphasis is placed on the process for fitting fragility curves to this data. This paper provides a synthesis of the most commonly used methods for fitting fragility curves and highlights some of their significant limitations. More novel methods are described for parametric fragility curve development (generalized linear models and cumulative link models) and non‐parametric curves (generalized additive model and Gaussian kernel smoothing). An extensive discussion of the advantages and disadvantages of each method is provided, as well as examples using both empirical and analytical data. The paper further proposes methods for treating the uncertainty in intensity measure, an issue common with empirical data. Finally, the paper describes approaches for choosing among various fragility models, based on an evaluation of prediction error for a user‐defined loss function. Copyright © 2015 John Wiley & Sons, Ltd.     

Seismic vulnerability assessment and characterisation of the buildings on Faial Island, Azores

The earthquake of the 9th of July 1998 that hit in the central group of the Azores archipelago greatly affected the islands of Faial, Pico and S?o Jorge, reaching a magnitude of Mw 6.2 with the epicentre located about 15km northeast of the Faial Island. This earthquake allowed the collection of an unprecedented quantity of data concerning the characterisation of the building stock and the damage suffered by construction. This is the main purpose of this research, consisting essentially of three main aspects: (i) A detailed characterisation of the building stock, assigning a five category classification, from old traditional rubble stone masonry to reinforced concrete moment framed buildings; (ii) A detailed damage grade classification based on the different damage mechanisms observed; and, (iii) A seismic vulnerability assessment of the building stock. The results of the vulnerability assessment together with the building stock database and damage classification were integrated into a GIS tool, allowing the spatial visualation of damage scenarios, which is potentially useful for the planning of emergency response strategies and retrofitting priorities to mitigate and manage seismic risk.