On the vulnerability assessment of monumental buildings

In all European countries the will to conserve the building heritage is very strong. Unfortunately, large areas in Europe are characterised by a high level of seismic hazard and the vulnerability of ancient masonry structures is often relevant. The large number of monumental buildings in urban areas requires facing the problem with a methodology that can be applied at territorial scale, with simplified models which need little easily obtainable, data. Within the Risk-UE project, a new methodology has been stated for the seismic vulnerability assessment of monumental buildings, which considers two different approaches: a macroseismic model, to be used with macroseismic intensity hazard maps, and a mechanical based model, to be applied when the hazard is provided in terms of peak ground accelerations and spectral values. Both models can be used with data of different reliability and depth. This paper illustrates the theoretical basis and defines the parameters of the two models. An application to an important church is presented.     

改进TOPSIS模型在城市地震脆弱性评估中的应用

针对目前仅以城市单体为对象研究城市地震灾害脆弱性,而忽视城市内部不同区域间存在特征差异的问题,选择威海市区作为研究对象,将研究范围细化至22个街道(镇),建立城市小区域地震灾害脆弱性评价模型。从人口、经济、建筑物和生命线系统4个方面选取17个指标构建城市地震脆弱性评价指标体系,应用主客观结合的三角模糊熵法和改进TOPSIS模型,计算出研究区域的相对贴近程度并进行排序,将威海市区划分为4个不同脆弱性等级。结果表明:改进TOPSIS模型能够从整体上对城市地震灾害脆弱性进行评级分区,为城市内部有针对性的制定防震减灾策略提供一个全新的思路。     

基于震害预测的动态震害矩阵方法研究

基于时间因素(材料内部作用、荷载作用和环境影响)和事件因素中的地震因素和抗震加固,通过结构可靠度理论研究和结构材料与构件的试验分析,结合现有的结构动态抗力函数以及不同极限破坏状态和结构抗力之间的对应关系,建立结构的动态易损性。研究事件因素中的拆迁和新建对城市建筑结构数量和类型的影响,以及未来城市不同结构类型的变化特点,给出未来城市的动态震害矩阵;研究群体震害矩阵的异地应用和事件因素中拆迁和新建建筑对震害矩阵的影响,在已有震害预测城市的建筑结构基础资料上,应用模糊数学中可信度方法,形成目标城市的动态震害矩阵,有利于进行结构的抗震设防和地震风险分析。     

城市典型建筑的地震损失预测方法Ⅰ: 结构易损性分析

地震作用下结构的易损性分析是地震灾害损失预测方法的重要组成部分。本文针对多层砌体房屋结构、排架结构和多层钢筋混凝土结构等3种城市典型建筑,首先给出了该类单体建筑的地震结构易损性分析方法,然后对群体建筑的地震易损性分析方法,以及群体建筑的易损性分类方法进行了探讨,为城市典型建筑的地震灾害损失预测和评估提供参考,并为宁波市抗震防灾规划的地震损失预测提供基础。     

城市典型建筑的地震损失预测方法I：结构易损性分析

地震作用下结构的易损性分析是地震灾害损失预测方法的重要组成部分。本文针对多层砌体房屋结构、排架结构和多层钢筋混凝土结构等3种城市典型建筑，首先给出了该类单体建筑的地震结构易损性分析方法，然后对群体建筑的地震易损性分析方法，以及群体建筑的易损性分类方法进行了探讨，为城市典型建筑的地震灾害损失预测和评估提供参考，并为宁波市抗震防灾规划的地震损失预测提供基础。     

四川省城市地震灾害脆弱性综合评价研究

城市化进程的不断推进使得城市的地震灾害脆弱性日益加剧,而城市承灾体的脆弱性受复杂因素影响。本文针对评价指标受主观性影响较大的问题,基于人口、工程、经济及社会4个方面,构建了城市震害综合脆弱性评价指标体系;并构建基于实码加速遗传算法优化投影寻踪（RAGA-PP）的城市震害脆弱性评价模型;最后,对四川省21个市、州进行了震害脆弱性评价。结果表明:巴中、南充等地脆弱性较高,成都、攀枝花等地脆弱性较低;经济因素对城市震害脆弱性影响较大;该评价模型能够克服人为主观性,有效可行。     

以徐州为例初探城市社会因素地震易损性分析

徐州是我国震害预测试点城市之一。影响城市震害的主要因素是城市所处的地质背景——地质因素和城市现状——社会因素。本文以现场调查资料为基础,以宏观震害经验为依据,考虑建筑物结构类型、建筑质量、建筑密度、人口、空旷场地、道路和危险工业等社会因素,运用多因素易损性(vulnerabiliy)分析法,完成了徐州市社会因素地震易损性分析,指出了该市抗震的薄弱环节和薄弱地区,为抗震防灾提供了依据。 地震易损性分析的结果是地震易损性分析图,总的易损性指数M是编制易损性分析图的依据。在总的易损性指数M中,建筑物易损性指数b占60—70%,其为建筑物易损性趋势矩阵A乘以建筑物组成矩阵B的转置阵矩阵B^T所得矩阵C的迹。     

Seismic risk in historical centers

In the first part the paper outlines the current conceptions relevant to seismic risk for constructions in urban centres analysing seismic hazard, vulnerability and exposure. In the second part there are some details about the vulnerability assessment of ordinary buildings, and about the differences that arise when monumental or historical buildings are in question. Then the concept of seismic scenario is given (third part), so that the specific question of seismic vulnerability of historical centres may be treated (part four), presenting an appropriate methodology recently proposed by the author. Finally part five presents an introduction to the theme of risk mitigation for historical centres and monuments, a very difficult question, where the two aspects of preservation and seismic safety must be considered together.     

地震和风耦合作用下上海中心大厦结构易损性研究

随着城市人口的增加,越来越多的超高层建筑在中国各大城市涌现,在其全寿命周期内不可避免的会遭受风甚至地震等多灾害的作用。以上海中心大厦为分析模型,根据其场地条件,采用Benowitez在2015年提出的1种基于随机波的模型方法模拟不同高度处具有空间相关性的脉动风荷载时程。通过对Perform 3D有限元软件建立的上海中心大厦模型进行非线性动力时程分析,研究地震和风耦合作用下对于结构性能的影响,并基于多灾害需求生成结构在地震和风耦合作用下的易损性曲面来研究结构的抗振可靠度。结果表明:结构的响应和易损性随着风速和PGA的增大而显著增大;随着风速的增大结构的响应和易损性均有增大的趋势,但随着地震动的增大,风荷载对结构响应和易损性影响逐步减小。     

The road map for seismic risk analysis in a Mediterranean city

The seismic risk analysis evaluation in the Mediterranean area is one of the main tasks for the preservation of Cultural Heritage and for the sustainable development of Mediterranean cities. The Mediterranean area is characterised by a medium–high level of seismic risk, so that earthquakes are the major cause for the destruction of monuments, residential and industrial buildings. A case history regarding the seismic risk analysis for the city of Catania (Italy) is presented, since the city has been heavy damaged in the past by strong earthquakes such as the 1169 earthquake (XI MCS), the 1542 earthquake (IX MCS), the 1693 earthquake (XI MCS) and the 1818 earthquake (VIII MCS) etc., which caused several thousands of deaths. Fault modelling, attenuation laws, synthetic accelerograms, recorded accelerograms and site effects are considered for the evaluation of the seismic action. Vulnerability of physical environment, related to the presence of cavities and to seismic-induced landslides and liquefaction has been analysed, with special reference to the new modelling of such phenomena and to the application of models to given areas. Soil–structure Interaction has been analysed for some geotechnical works, such as shallow foundation and retaining wall, by means of physical and numerical modelling. The paper deals with the vulnerability of physical environment (landslides, liquefaction, etc.), while the road map continues with the analysis of vulnerability of monuments and buildings, with the aim of the estimation of the seismic resistance required to defend against the seismic action given by the scenario earthquake. For the mitigation of seismic risk, structural improvements of R.C. buildings with different methodology and techniques have been analysed, as well as the guideline for the strengthening of buildings. The work shows that the seismic risk of the city is not a summation of the seismic risk of each building, because the vulnerability of the urban system plays an important role on the seismic risk evaluation of a given city. To this aim the vulnerability of the road infrastructures, lifelines, and urban framework have been also analysed in the project.     

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.     

Multiplication factor for open ground storey buildings–a reliability based evaluation

Open Ground Storey(OGS) framed buildings where the ground storey is kept open without infill walls, mainly to facilitate parking, is increasing commonly in urban areas. However, vulnerability of this type of buildings has been exposed in past earthquakes. OGS buildings are conventionally designed by a bare frame analysis that ignores the stiffness of the infill walls present in the upper storeys, but doing so underestimates the inter-storey drift(ISD) and thereby the force demand in the ground storey columns. Therefore, a multiplication factor(MF) is introduced in various international codes to estimate the design forces(bending moments and shear forces) in the ground storey columns. This study focuses on the seismic performance of typical OGS buildings designed by means of MFs. The probabilistic seismic demand models, fragility curves, reliability and cost indices for various frame models including bare frames and fully infilled frames are developed. It is found that the MF scheme suggested by the Israel code is better than other international codes in terms of reliability and cost.     

A recursive decomposition algorithm for network seismic reliability evaluation

A new probabilistic analytical approach to evaluate seismic system reliability of large lifeline systems is presented in this paper. The algorithm takes the shortest path from the source to the terminal of a node weight or edge weight network as decomposition policy, using the Boolean laws of set operation and probabilistic operation principal, a recursive decomposition process then could be constructed. For a general weight network, the modified Torrieri method (NTR/T method) is introduced to combine with the suggested algorithm. Therefore, the recursive decomposition algorithm may be applied to evaluate the seismic reliability of general lifeline systems. A series of case studies, including a practical district electric power network system and a large urban water supply system, show that the suggested algorithm supplies a useful probabilistic analysis means for the seismic reliability evaluation of large lifeline systems. Copyright © 2002 John Wiley & Sons, Ltd.     

Seismic vulnerability and risk assessment: case study of the historic city centre of Coimbra, Portugal

Seismic risk evaluation of built-up areas involves analysis of the level of earthquake hazard of the region, building vulnerability and exposure. Within this approach that defines seismic risk, building vulnerability assessment assumes great importance, not only because of the obvious physical consequences in the eventual occurrence of a seismic event, but also because it is the one of the few potential aspects in which engineering research can intervene. In fact, rigorous vulnerability assessment of existing buildings and the implementation of appropriate retrofitting solutions can help to reduce the levels of physical damage, loss of life and the economic impact of future seismic events. Vulnerability studies of urban centres should be developed with the aim of identifying building fragilities and reducing seismic risk. As part of the rehabilitation of the historic city centre of Coimbra, a complete identification and inspection survey of old masonry buildings has been carried out. The main purpose of this research is to discuss vulnerability assessment methodologies, particularly those of the first level, through the proposal and development of a method previously used to determine the level of vulnerability, in the assessment of physical damage and its relationship with seismic intensity. Also presented and discussed are the strategy and proposed methodology adopted for the vulnerability assessment, damage and loss scenarios for the city centre of Coimbra, Portugal, using a GIS mapping application.     

Presentation of RISK-UE Project

This paper is a presentation of an European project called RISK-UE, entitled: “An advanced approach to earthquake risk scenarios with applications to different European towns”. It gives the origin, the objectives and the organisation of the project, together with the content of the different workpackages comprising methodological aspects: different features of European town, seismic hazard, urban system exposure, vulnerability of current, historical and monumental buildings, vulnerability of lifelines and essential facilities, seismic risk scenario, with an application to the seven following cities: Barcelona, Bitola, Bucharest, Catania, Nice, Sofia and Thessaloniki. These studies were realized in close relation with the decisionmakers of these cities, in order that they implement Risk Management Plans and Plans of Action to effectively reduce seismic risk.     

A simplified approach for vulnerability assessment in moderate-to-low seismic hazard regions: application to Grenoble (France)

Due to the moderate seismic risks in France, the building vulnerability assessment methods developed for high seismic risk countries could not easily be used here because of their cost and the low-risk perception among the public and officials. A light vulnerability assessment method is proposed and tested in Grenoble (France), based on classes and scores provided in the GNDT method but simplified in terms of visual screening and number of structural parameters used. Compared to the RiskUE method, the damage obtained by our approach shows that 90% of buildings have residuals smaller than 0.2, i.e. one grade of the EMS98 damage scale. A large scale survey is devised and conducted among the inhabitants of Grenoble in order to collect the main structural parameters. By comparing the results from the survey to the historical urbanization of Grenoble and to expert surveys performed in two urban districts, the information useful for the light method of vulnerability assessment can be rapidly collected by non-experts reducing substantially the estimate cost. The average damage is then computed using the GNDT formula considering the probable intensities which could be observed in Grenoble (VII and VIII). The average damage reaches 0.4 in the oldest part of Grenoble mainly made of masonry buildings and 0.2 in reinforced concrete suburbs where reinforced concrete predominates. The results are a relative vulnerability assessment that provides useful initial information for the urban zones of Grenoble where the vulnerability is higher. This method can be used to classify the seismic vulnerability in wide seismic-prone regions to a fair degree of accuracy and at low cost.     

城市抗震设防标准的优化

本文提出了城市抗震设防标准的优化方法, 该方法利用了建筑结构的易损性分析理论, 初始造价与设防烈度的关系, 地震设防时增加的经济投入与设防烈度的关系, 地震经济损失与设防烈度的关系等, 根据抗震设防增加的经济投入与地震经济损失之和最小的模型得到经济最优设防烈度, 并以按经济最优烈度设防时地震中的人员伤亡率小于社会可接受地震人员死亡率为限制条件, 求得最优设防烈度。     

基于空间分析技术的海岛地震灾害风险分析研究

我国约有1.1万个海岛,多处于地震活跃带,地震灾害特征明显,目前地震领域研究主要针对城市展开,海岛地震灾害风险的研究较少。此背景下,该研究收集了海岛地震相关的地质和地震数据,形成海岛地震灾害空间数据库;从地震危险性、承灾体易损性和防震减灾能力3个方面构建海岛地震灾害风险评价指标体系;利用ArcGIS空间分析技术,采用熵权法与AHP法相结合建立海岛地震灾害风险综合评价模型,以长岛县、洞头区和东山县为例进行分析,并将海岛地震灾害风险等级划分为4个等级。结果显示:东山县为地震灾害高风险区,洞头区和长岛县为地震灾害较低风险区。该研究对海岛工程抗震规划与设计有重要意义。     

The role of the urban system dysfunction in the assessment of seismic risk in the Mt. Etna area (Italy)

A procedure for seismic risk assessment is applied to the Mt. Etna area (eastern Sicily, Italy) through assessment of urban system dysfunction following the occurrence of an earthquake. The tool used is based on the Disruption Index as a concept implemented in Simulator QuakeIST, which defines urban disruption following a natural disaster. The first element of the procedure is the definition of the seismic input, which is based on information about historical seismicity and seismogenic faults. The second element is computation of seismic impact on the building stock and infrastructure in the area considered. Information on urban-scale vulnerability was collected and a geographic information system was used to organise the data relating to buildings and network systems (e.g., building stock, schools, strategic structures, lifelines). The central idea underlying the definition of the Disruption Index is identification and evaluation of the impact on a target community through the physical elements that most contribute to severe disruption. The procedure applied in this study (i.e., software and data) constitutes a very useful operational tool to drive the development of strategies to minimise risks from earthquakes.