This paper presents damage fragility curves derived through an analytical approach for reinforced concrete building classes representative of the existing Italian building stock. Fragility curves are generated by adopting a fully probabilistic framework that relies on a cloud-based approach employing real ground motion records and allows accounting and propagating the main sources of uncertainty. The seismic performance of masonry-infilled reinforced concrete frames is estimated via nonlinear time-history analyses performed via a simplified multi-degree-of-freedom model named STICK, in which the behavior of the frame is concentrated at the storey level. Thanks to the versatility of the adopted analytical model and its reduced computational burden, the effect of the main uncertainties that are typically neglected or only partially considered during the generation of analytical fragility curves is accounted for within the framework. Specifically, the inter-building, intra-building, and record-to-record variabilities, as well as variability related to the definition of the building damage level are explicitly considered. Fragility curves are developed for Damage States compatible with the EMS98 scale as a function of the peak ground acceleration for building classes defined adopting as main attributes the number of storeys, the age of construction, the design level, and the typology of infill panels. The proposed fragility curves are also compared with existing empirical ones showing a good agreement that confirms the validity of the proposed framework.

The development of building inventory is a fundamental step for the evaluation of the seismic risk at territorial scale. Census data are usually employed for building inventory in large scale application and their use requires suitable rules to assign buildings typologies to vulnerability classes, that is an exposure model specific for the considered vulnerability model. Several exposure models are developed proposing class assignment rules that are calibrated on building typological data available from post-earthquake survey data. However, this approach has the drawback of being based on data from specific geographic areas that have been hit by damaging earthquakes. Indeed, the distribution of building typologies can vary greatly for different areas of a country and the diffusion of one building’s typology rather than another one may depend on the availability of construction material in the area, the evolution of construction techniques and the codes in force at the time of construction. This paper aims to improve the exposure modelling at regional scale, investigating the variability of masonry building typologies distribution. It proposes a methodology to recalibrate the exposure models at regional scale and evaluates the influence of the improved characterization of regional vulnerability on damage and risk assessment. The study shows that the analysis of local building typologies may strongly impact on the evaluation of the seismic risk at territorial scale.

The prediction of seismic performances of buildings in terms of engineering demand parameters EDP, such as interstorey drift ratios IDR and peak floor accelerations PFA, represents a fundamental step towards the assessment of potential direct economic losses. This paper proposes a simplified model for the rapid assessment of EDPs in infilled moment resisting frames subjected to seismic loadings suitable for large scale assessment studies. The proposed model, named Stick-I (Stick model for Infilled frames), is a mull-degree of freedom MDOF system consisting of a series of lumped masses connected by means of nonlinear shear link elements. The shear link behavior is suitably calibrated adopting a multi-objective Genetic Algorithm procedure that employs the results of nonlinear cyclic pushover analyses performed on refined nonlinear FEM. Based on the regression study performed on a suitably generated Stick-I model database, a more general Stick-IT model, representative of RC Infilled frame Typologies of assigned storey number and dimensions in plan, is introduced. Simplified formulas for the definition of Stick-IT model are proposed depending on low-level information data that can be easily retrieved from rapid on-site surveys or remote sensing techniques. Both Stick-I and Stick-IT models are validated comparing the results of NRHA performed on refined FEMs with the results obtained adopting the simplified models and good agreement in terms of maximum EDP values and distribution along the building height is obtained. The typological Stick-IT model, which is defined as a function of few geometric and mechanical parameters, can be easily applied for simplified evaluation of expected response for building typologies. Hence, it can also be usefully employed for assessment of direct losses at the large scale, with a significant reduction in computational burden with respect to more refined methods.

This study focuses on the seismic vulnerability assessment of the Italian residential building stock, by taking advantage of post-earthquake damage data collected after past Italian seismic events of the period 1980-2009. Starting from the typological classification of the existing building stock, five vulnerability classes, three for masonry (i.e. A, B, C1) and two for reinforced concrete (i.e. C2 and D) buildings, are identified, grouping buildings exhibiting similar seismic behaviour. Seismic vulnerability is described by correlating empirically-derived damage index (DI) values and the peak ground acceleration, representing the selected ground motion intensity measure. To this aim, candidate functional forms are the lognormal and the exponential models. The accuracy of pre-selected functional forms to reproduce the observed seismic DI is demonstrated via graphical diagnostic and quantified in terms of a coefficient of accuracy. Parameters defining the proposed vulnerability functions are also provided. The results presented in this paper could be used in other regions having similar seismic hazard and built environment.

This paper investigates on the effect of story lateral stiffness variation on the maximum elastic interstory drift ratio ( IDR max ) for existing reinforced concrete ( RC ) buildings. Several classes of existing gravity load designed RC buildings are obtained via a simulated design approach. The presence of infills in the perimeter frames as well as different opening percentages along the height are considered. A simplified elastic analysis is performed, adopting an equivalent multistory cantilever system to represent the stiffness variation along the buildings height. IDR max is significantly influenced by the ratio of the lateral stiffness at the second and upper stories over the lateral stiffness of the first story. Such a ratio has been found dependent on a number of geometric and configuration factors, including the variation of the opening percentage ratio. Two regression formulas are proposed to estimate, given the spectral displacement at the fundamental period T , the roof displacement and IDR max as a function of the building height and the opening percentage at first and upper stories. Suitable modification of the formulas is also introduced to account for possible cracking of RC elements and infill panels even at very low levels of lateral drift. These expressions could be used for the simplified evaluation of the expected drift demands for buildings of existing RC typologies. Finally, the proposed formulations are applied to a number of permanently monitored buildings, comparing the calculated IDR max with the one resulting from record processing, obtaining a fair good agreement.

Limitation of monetary losses due to earthquakes can improve resilience in developed countries. Computation of losses with the PEER performance-based earthquake engineering framework (Porter 2003) normally entails performing a number of Non-linear Response History analyses as a basis for assessment of expected Engineering Demand Parameters and associated losses, that is an elaborate and time-consuming task. In (ATC 2012) an alternative quicker approach relying on simplified modeling and analysis with SPO2IDA is also envisaged. This paper tests the applicability of simplified method using pushover based analysis and CSM method. In particular, it compares the losses obtained for a non-conforming reinforced concrete moment frame building starting from the classical approach, i.e. based on Non-linear Response History analyses, with the one computed with pushover-based assessment. Moreover, it evaluates the reduction of losses after building retrofit with the pushover-based analysis.

In (FEMA 308 in Repair of earthquake damaged concrete and masonry wall buildings, Prepared by ATC for the Federal Emergency Management Agency, Washington DC, 1998) a general framework facilitating decisions on appropriate course of action (accept damage, restore, or upgrade) for damaged buildings after an earthquake was presented. Such Performance-Based Policy Framework relies on performance index of the building in its intact and damaged state and on the relative performance loss as significant indicators for repair and/or upgrade decisions; however, no specific guidance for the establishment of PL and IP thresholds governing damage acceptability was given. This paper proposes an improvement of the PBPF introduced in FEMA 308 by providing it with a set of performance thresholds that can be established based on a clear quantitative approach and presents a set of tools for its practical implementation with reference to Reinforced Concrete frame buildings. In addition to the Repair and Repair and Retrofit options, also the Demolish one is introduced, because it corresponds to a not infrequent decision in case of severely damaged buildings in European-Mediterranean regions. Criteria to establish decision thresholds IP and PL are proposed that allow to clearly connect them to reconstruction costs and probability of failure of the building in the intact and damaged state. Finally, a case study demonstrates the application of the hypothesized policy framework for a Municipality in southern Italy and investigates on the effects of varying decision thresholds on the total reconstruction costs and mean safety level for the considered building stock.

The evaluation of building reparability after damaging earthquakes is a complex issue, involving factors such as the damage state, residual capacity and post-earthquake safety, initial performance level with respect to design earthquake and repair and retrofit costs. In the post-earthquake reconstruction process after the 2009L’Aquila earthquake, the funding request had to be accompanied by a detailed assessment of repair costs, the pre-earthquake safety level with respect to new building standard (%NBS) and, if needed, by a detailed design of retrofit intervention and costs. The paper examines the database of severely damaged buildings after L’Aquila, collecting information of repair and retrofit costs as well as the final decision on reparability or demolition and reconstruction; 122 out of 472 severely damaged RC buildings were demolished. It illustrates the most important factors influencing demolition decisions for Reinforced Concrete (RC) buildings. A logistic regression is performed to estimate the probability of demolition pdem for building typologies. Considering pre-earthquake information, the construction age is the most influential parameter, with older buildings having a higher pdem. Another significant parameter is %NBS. Considering post-earthquake information, the repair cost is expectedly the most important parameter. It results that pdem can be expressed as a function of construction age, %NBS and repair costs. A case study illustrates the possible application of the results for a town district in Campania Region, southern Italy.

High Performance Scientific Computing Using Distributed Infrastructures, pp. 281-289 (2017) No AccessChapter 24: Computation of TR-Dependent Aftershock Fragility Curves for an Existing Non-Ductile R.C. BuildingM. Gaetani d'Aragona, M. Polese, A. Prota, and G. ManfrediM. Gaetani d'AragonaUniversity of Naples Federico II, Naples, Italy, M. PoleseUniversity of Naples Federico II, Naples, Italy, A. ProtaUniversity of Naples Federico II, Naples, Italy, and G. ManfrediUniversity of Naples Federico II, Naples, Italyhttps://doi.org/10.1142/9789814759717_0024Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: In the aftermath of a damaging event, the structural safety against future earthquakes may be significantly reduced. An indirect measure of building seismic safety in its intact and damaged state is represented by the Residual Capacity (REC) index that quantifies building seismic capacity at collapse. This study investigates, by means of a detailed case study, the expected variation of REC for increasing seismic demand. The response of an existing non-ductile reinforced concrete building is simulated using a multi-degree-of-freedom (MDOF) finite element model that properly accounts for brittle failures. Different definitions of building collapse are introduced and consistent assessment of building REC are performed. FiguresReferencesRelatedDetails High Performance Scientific Computing Using Distributed InfrastructuresMetrics History PDF download

When a seismic event occurs, damage may accumulate in a building affecting its capacity to withstand future earthquakes. This study investigates, by means of a detailed case study, the advantages related to the application of structural retrofit prior of earthquake events in terms of structural safety variation due to damage. The response of an existing non-ductile RC frame in California is simulated using a refined finite element model that properly accounts for possible brittle failures of structural members. Furthermore, the actual structural capacity is evaluated accounting for typical collapse modes that can affect the behavior of non-ductile buildings. Different retrofit strategies have been adopted and damaging earthquake scenarios considered. The future seismic performances of retrofitted structure before damage are compared with the case in which no mitigation strategies have been adopted showing the advantages of different categories of intervention for different earthquake scenarios.

Decisions on reparability for damaged buildings after an earthquake are often controversial, and they should properly take into account the variation of building safety level due to damage and the repair costs.A significant indicator for the appropriate course of action is the so-called Performance Loss (PL), that is a measure of seismic safety decay.PL can be determined as a function of the variation of building seismic capacity from the intact to damaged state.This study investigates, by means of a detailed case study, on the expected PL for increasing seismic demand and its relationship with varied building safety level and repair costs.We simulate the response of an existing non-ductile reinforced concrete building using a finite element model that properly accounts for both flexural, shear and axial failure of members and accounts for joints behavior.Different definitions of building collapse are introduced, and Incremental Dynamic Analyses are performed with a representative set of input ground motions both for the intact and damaged structure.In order to evaluate aftershock fragilities, multiple Mainshock-Aftershock sequences are built through suitable scaling of selected accelerograms.Fragility curves for the intact building and the aftershock fragility curves are used to evaluate PL and the variation of collapse probability for main-shocks of increasing return period TR.Also, corresponding repair costs are determined.The study shows interesting relations between damage levels and repair costs that may be simulated with detailed analyses and associated PL, representing a first insight in the establishment of relations between PL and repair and/or upgrade decisions.

Seismic behavior of damaged buildings may be expressed as a function of their RE- sidual Capacity (REC). The residual capacity REC Sa is defined as the minimum spectral acce- leration (at the period T eq of the equivalent SDOF) corresponding to building collapse. When referring to peak ground acceleration a g as damaging intensity parameter, REC ag is defined as the minimum anchoring peak ground acceleration such as to determine building collapse. For a given spectral shape, REC ag corresponds to REC Sa scaled by the spectral amplification factor for T eq . REC Sa and REC ag , generally indicated as REC, lower with increasing damage level in buildings; hence REC may be very useful in estimating the post-seismic building safe- ty. In a recent work (1) it has been shown how it is possible to derive REC (REC Sa and REC ag ) through Pushover Analyses (PA), where a suitable modification of plastic hinges for damaged elements is applied. The applicability of PA for damaged structures is verified in (2) by com- parison of the PA results with those on nonlinear time-history analyses. On the other hand, it is unrealistic that in the aftermath of an earthquake, when the assessment of building safety has to be performed in an emergency situation, there would be time for the execution of de- tailed nonlinear analyses. Acknowledging the need for easier and faster evaluation tools, in (3) a simplified MEChanism based method (MEC) for evaluating the building REC was pre- liminary tested. The present work extends the comparison of the results (in terms of REC), that could be obtained by PA and MEC analyses, considering a number of Reinforced Con- crete (RC) frames building typologies. Moreover, by adopting the MEC approach, the possi- ble variation of REC as a function of seismic demand is investigated. The simplified method can be used to explore the possible ranges of REC variation for RC building classes consider- ing the anticipated mechanism formation after an earthquake; in addition, it could be used in the post-seismic phase for estimating the REC of damaged buildings having undergone identi- fiable plastic mechanisms and for fast assessment of damage-dependent collapse fragility curves.

Seismic behavior of damaged buildings may be expressed as a function of their REsidual Capacity (REC ag ), that is a measure of seismic capacity "reduced" due to damage and represented in terms of peak ground acceleration a g. REC ag may be estimated through pushover analyses. In fact, adopting a lumped plasticity model, the plastic hinges may be suitably modified to account for the damage level of the single elements (1); as shown in (2) nonlinear static analyses of the modified damaged models yield pushover curves that, depend- ing on the number of elements involved in the damaged mechanism and on their damage level, may differ significantly with respect to original ones. The applicability of Pushover Analyses (PA) has been demonstrated for regular structures (3, 4), with their significance being gener- ally supported by the comparison of the results obtained by these "simplified" analyses with Nonlinear dynamic Time-History (NTH) analyses. However, the usability of pushover analy- sis for the assessment of the behavior of damaged buildings has not been verified yet, and the study presented in this paper aims at contributing in the evaluation of this issue. The results of PA are confronted with those of NTH for Multi Degree Of Freedom (MDOF) systems rep- resentative of existing R.C. building typologies in the Mediterranean regions. In particular, the response (and damage) of each one of the original "intact" MDOF systems for earth- quakes of increasing intensity is studied with either the PA and NTH. Next, applying the methodology described in (2), damage dependent behavior is estimated for varying levels of initial seismic (damaging) intensity. The maximum inter-storey drift and shape along the height, as well as the "modified" REC ag are compared to the ones that could be obtained with NTH by subsequent application of suitably scaled pairs of accelerograms . The results of this study suggest that degree of approximation that is obtained by PA applied to damaged struc- tures with respect to NTH does not vary with respect to the approximation of standard PA compared to NTH.

Seismic fragility curves play a critical role in risk assessment because they represent the probability of attaining different damage states given the ground motion intensity. However, in case of repeated earthquakes, the seismic vulnerability of buildings varies due to damage and this shall be properly considered for the realistic estimate of evolving seismic risk during a seismic sequence. This paper presents a methodology for the assessment of damage-dependent fragility curves for existing reinforced concrete (RC) building classes. The derivation of fragility curves is based on a hybrid method that combines observational based “empirical” curves and mechanical based assessment of buildings’ residual capacity (REC), that is a measure of seismic capacity, which may be reduced due to seismic damage. A mechanism based procedure to assess building REC, and its variation for increasing ductility demand, is presented. Then, in order to be able to apply such procedure to RC building classes, a simulated design procedure is implemented that allows the automatic design of elements dimensions and reinforcement, as well as the characterization of the building nonlinear model needed for mechanism based analysis. Applying a Monte Carlo simulation procedure the geometric, structural and mechanical parameters, from which the design depends on, are varied according to representative distributions and populations of building models are generated and analyzed with mechanism based approach. The procedure is implemented for buildings that are prone to first storey mechanism and is applied for existing RC building classes in L’Aquila.

The CRISMA project (www.crismaproject.eu) is a European Union funded project focusing on the simulation of multi-sectoral large scale crisis scenarios that have multi-dimensional effects on society and people.The project aims at the development of a framework to build use case specific tools which will allow decision-makers to cross-examine dynamic crisis scenario evolutions, to set action parameters of operational and strategic activities, and to visualise impacts and crisis evolvement.This will be achieved by providing a modular and open software framework to build planning and decision support systems for modelling and simulating realistic crisis scenarios and their possible consequences.CRISMA applications simulate and analyse the development of a simulated "World" in a crisis management context.A World is defined as a coherent set of data, simulation models operating on this data and the model control parameters governing the activity of these models.A snapshot of the World, or World State, consists of all data related to a specific crisis simulation experiment.This includes a set of information to control simulation models operating on the World data as well as a set of condensed, representative and quantitative information that can be used for a qualitative assessment of a world state.The user can influence a crisis evolvement by changing control parameters of the simulation models.Every modification of a World State is considered a distinct decision point and eventually produces a new World State.This leads to a decision tree.The architectural design approach uses several concepts from previous projects focusing on reference models, reference architectures and simulation-specific standards.For the CRISMA architecture, the project adopts certain common concepts that support a systematic architectural design process.In order to demonstrate and validate the design, five pilot sites are used to provide experimentation for validation and testing of a wide range of crisis management situations (coastal floods, extreme weather conditions, geophysical hazards, multi-organisational and cross-border cooperation in crisis management, planning and training for resource management).Piloting will include multi-risk and domino effects.The paper presents the business logic and key aspects of the CRISMA architecture.The work presented is work in progress, published during the design stage of the architecture.Implementation will be under way during the MODSIM 2013 conference.

Seismic behavior of damaged buildings may be expressed as a function of their REsidual Capacity (REC), that is a measure of seismic capacity reduced due to damage; the diminishing of REC after an earthquake is representative of Performance Loss PL. This paper deals with the problem of assessing building’s REC for existing under-designed Reinforced Concrete (R.C.) buildings that are typically found in European Mediterranean regions. REC is evaluated based on pushover curves obtained for the structure in different damage state configurations, where building’s behavior is simulated with a suitable modification of plastic hinges for damaged elements. Moreover, a simplified approach for REC assessment, that may be useful for a preliminary evaluation of possible damage dependent PL, is proposed.

Seismic risk assessment on a large scale may be defined as the prediction of the fraction of buildings expected to reach a conventional limit state in the region and time period of interest. This definition is the frequentistic interpretation of the failure probability for a homogeneous class of structures. Empirical post-event survey methods for vulnerability evaluation may not fit the purpose of seismic risk analysis at class level and a pure analytical approach may be required; to this aim this paper proposes the extension of structure-specific reliability procedures. The classcapacity function is approximated by regression of significant cases analyzed by Static Push-Over (SPO); the seismic demand is obtained by Probabilistic Seismic Hazard Analysis (PSHA). The seismic risk is computed by simulation of the former being exceeded by the latter via the Capacity Spectrum Method (CSM). Explanatory application refers to six classes of Italian rectangular R.C. buildings; three classes are of pre-code constructions, designed only for gravity loads, whereas the other three consider seismic buildings designed with old codes not accounting for capacity design concepts.

This paper presents the general criteria and implementation of an automatic procedure to evaluate the seismic capacity of existing reinforced concrete (RC) regular buildings. The method represents a useful tool in the framework of mechanical based vulnerability assessment methods. In particular, the seismic capacity is retrieved via pushover analyses on a lumped plasticity model for the building. Unlike recent approaches that rely on a single representative structural model for an entire building population, the proposed method allows virtually all the buildings of the population to be analysed in an automatic loop. With the aim of expediting and automatizing the analysis process, a dedicated software was implemented, whose main functions are: identifying possible structural systems compatible with regular building shapes of assigned dimensions and designing its elements in terms of cross-section and reinforcement; constructing the related nonlinear model and performing pushover analyses in order to determine synthetic capacity parameters useful for preliminary vulnerability assessment at a large scale. The software application and potentialities are shown in an example for the generic building of a class.

大多数情况下地震风险评估被定义为对房屋破坏情况的预测,这些地区的房屋是按照一种传统极限状态的设计要求而建造的。这个定义可以解释同一等级房屋的失效概率。为评估薄弱处而做的基于经验的灾后调查方法可能并不能满足这种基于房屋等级的地震风险分析的目的,需要提出新的分析方法。为此提出了改进的结构可靠性分析方法。根据静力弹塑性分析（SPO）结果,结构中产生的一些显著事件会导致结构退化,由此可以在能力曲线中定义相应的房屋等级;地震需求从概率性地震危害分析（PSHA）中确定。通过能量谱方法（CSM）模拟结构从初始状态发展到破坏状态的过程可以计算出结构的地震风险程度。分析模型选取了6类位于意大利的钢筋混凝土矩形建筑;其中3类是按照老规范建造的,设计中只考虑了重力荷载,另外3类是按老规范设计的抗震房屋。

世界上有些火山地震位于人口密集区,因此与喷发前地震活动有关的地震危险性及其对工程结构的潜在破坏应该是危险性评估及管理的一部分。维苏威火山(意大利南部)就是如此,在那里数十万人面临火山及相关的地震危险的威胁。通过对维苏威火山地震活动相应的震级、震中及震源机制进行地震波形的大量模拟,本文研究了喷发前地震活动的影响。进行地震合成处理,以求得强地面运动特征参数,这有利于估计建筑物多的地区由期望的最大单个地震事件和大量小地震的累积效应所造成的地震破坏。选择一组所记录的地震比较合成的和观测的强地面运动参数,以证实模拟方法是否可靠。由于在维苏威地区下面的浅深度存在明显的速度不连续性,不同距离的峰值地面加速度(PGA)似乎受地震深度的影响。另一方面,滞后能量谱与结构物的塑性变化有关,它明显取决于古登堡—里克特定律(G-R)的b参数。1997年在意大利翁布里亚—马尔凯发生的地震(M5·8),虽然并未记录到很大的峰值地面加速度值,但却造成了建筑物和基础设施的严重破坏,通过在合理的期望范围内改变G-R定律参数,我们注意到累积滞后能量与在翁布里亚—马尔凯震源附近的观测值是相当的。