8.Mauro Dolce Vulnerability x
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Vulnera bility evaluations for seismic risk assessment (Mauro Dolce, Dipartimen to della Protezione Civile) Seismic risk is a public sa fe ty issue that req uires ap pr opriate risk management measures and means to protect citizens, properties, infrastructures and the built cultural heritage. The aim of a seismic risk analysis is to estimate the consequences of seismic events on a geographical area (a city, a region, a state or a nation in a certain period of time. The e!ect to be predicted is the physical damage to buildings and other facilities, together "ith the consequences of the physical damage# the number and type of casualties, the potential economic losses, due to the direct cost of damage and to indirect economic impacts (loss of the productive capac ity and business int err upt ion, the loss of function in lif elines and critical facilities (such as hospital, $r e stations, communication system, transportation net"orks, "ater supply, etc. and also social, organizational and institutional impact. The results provided by seismic risk analysis are used in all the phases of the emergency cycle# before, during and after the event. %ne of the main factors in loss assessment is the seismic vulnerability of buildings, i.e. the susceptibili ty of buildi ngs to su!er a certain damage level if sub& ected to an earthquake. Since the building behaviour is not deterministic, the su!ered damage is to be considered as a random variable. 'ence building vulnerability is epressed as the probability of reaching or eceeding a speci$ed damage level, given an intensity measure of the earthquake. )ntuitively, the more the building is vulnerable, the higher "ill be the su!ered damage, given the same seismic intensity. )n operative terms a vulnerability method should correlate the seismic intensity to the physical damage su!ered by the building, depending on the structural, geometric, and technological building features. Despite the simple and st raight for"ar d de$nition, several methods for vulnerabil ity assessment have been develo ped and pr opo sed in recent yea rs. *onsequently, several have been the attempts to provide classi$cation criteria for them +-D/-)D%, 0123, *orsanego and etrini, 01145 Dolce et al. 01145 Dolce, 0116, Di asquale et al., 7880, *alvi et al., 78869. :lmost all the classi$cation criteria agree on the distinction bet"een three types of vulnerability approaches, "hen reference is made to the genesis of the methods# ; empirical vulnerability methods, based on post;earthquake damage observations or laboratory tests5 ; mechanical vulnerability methods, based on structural mechanical models5 ; method based on epert &udgment or Delphi methods. <ach one of these approaches is di!erently characterized by positive features and limitations. %bserved vulnerability methods are based on statistics of past earthquake damage data and usually lead to the de$nition of DM=s, i.e. Damage robability Matrices +>ithman, 01?@5 Ara ga et al., 01275 Bossetto and <lnashai, 788@9, or direct ly to frag ilit y curves +*oburn and Sp enc e, 01179. %ne dra"back of the approach is that data are often limited to the building typologies and to the felt
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seismic intensities in the a!ected area. %n the contrary mechanical models may beused to analyse any type of building for anyseismic intensity. 'o"ever they reCect the building response according to the modelor to the seismic code and not to the real seismic behaviour, and "ithoutdi!erentiating bet"een partial and total collapses.
The $rst systematic attempt to codify the seismic vulnerability of buildings
completely from epert &udgment "as made by the :pplied Technology *ouncil,providing DM for ?2 engineering facility classes, 48 of "hich "ere relevant tobuildings (:T*0@, 012?. )n this case dra"backs arise from the lack of any directcheck or derivation "ith reality, apart from the eperience cumulated by the epert.'ence recent approaches have also considered the possibility of hybrid techniques,"hen empirical observations are used to condition mechanical vulnerabilityevaluations +appos et al. 01169.
:nother important di!erence among methods is the number of buildings themodel refers to. This is strictly related to the accuracy of the building informationrequired in the model. )t is possible to epressvulnerability &ust for one building. )n this case a detailed building representation isrequired and an accurate prediction is epected. The data collection is quite
cumbersome since the eact geometry andmost of the structural details, as "ell as the material properties, are required to bekno"n. Eor instance inB* buildings the size and position of beams and columns, reinforcement details,concrete and steelstrengths are required to make reliable models. This procedure is not obviouslyapplicable "hen theresponse of a huge number of buildings is to be predicted. )n this case, according tohuman resources, onlythe most important parameters can be collected. 'ence models have to be,necessarily, more simpli$edand, consequently, less accurate. )n this case similar buildings are often grouped in
classes of buildings and the same model refers to all the buildings belonging to thesame class. 'ence "ithin the same class, one building is not distinguishable fromanother.
This means that "hen performing loss analysis at di!erent scale of analysis(single building, local or territorial scale it is not possible to operate "ith the samevulnerability method. %n the other hand,usually, a multi;level approach is introduced, "here progressively more accuratemethods are used as thenumber of buildings to be investigated decreases. :s an eample in Bisk;< pro&ect+Fagomarsino andGiovinazzi, 78869 t"o di!erent approaches have been proposed# a ) level approachto be used "ith macroseismic intensity hazard scenarios and a )) level approach,
mechanical;based, for G: and responsespectra hazard scenarios. %ther eamples may be found in +Goretti et al., 788?5Grant et al., 788?, *osenza et al., 78839. )n the distinction bet"een model accuracyand data required, the problem of uncertainty of the model has seldom beaddressed. )n other "ords, in practice models have been selected and data havebeen collected based on personal eperience, "ithout any study on the bene$t of introducing or removing several parameters in the model "ith respect to the desiredaccuracy of the prediction.
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:nother important distinction has to be made bet"een primary and secondaryvulnerability +Di asquale and Goretti, 78809. >hile primary vulnerability providesthe probability of su!ering a physical damage conditional to building type andseismic intensity, secondary vulnerability provides the probability of losses(economic, functional, etc given the building type and the su!ered damage. Theconvolution of the primary and the secondary vulnerability provides the total
vulnerability that is the building susceptibility to su!er losses from earthquakes.Some models provide the only primary vulnerability, some others provide the totalvulnerability. )t is the case, for eample, of the etrini model +Guagenti and etrini01219, that provides the mean relative economic loss due to the earthquake.
Sometimes in loss assessment the model used for the primary and secondaryvulnerability are provided by di!erent authors. )n this case it is important to checkthe internal consistency of the model. )thas been sho"n +Di asquale and Goretti, 78809 that the secondary vulnerabilitymay signi$cantly di!ers"hen di!erent measures of physical damage are considered# the mean damage tovertical bearing structures, the maimum damage to vertical bearing structures or amean structural damage that takes into
account a "eighted sum of the damage su!ered by each building structuralcomponent. 'ence it happensthat it is not possible to couple a primary vulnerability model "ith a secondaryvulnerability model, if thedamage measures are not the same. 'o"ever, this simple and quite obviousconcept has been oftendisregarded in applications.
Several other important di!erences among eisting models regard thedamage variable and theintensity variable. Aoth can be discrete or continuous. <ample of discrete damage;discrete intensitymodels are the so;called DMs +Araga et al., 01279, "here damage ranges usually
bet"een 8 (no damageto 3 (the total collapse, and intensity is epressed in terms of macroseismicintensity ranging fro H to I)).
The numerous di!erent macroseismic scales that have been used in the pastto assess vulnerability (M*S, MM, MS, <MS12 further complicate a comparisonbet"een di!erent methods. :n eample of discrete damage;continuous intensitymodel is the one presented in +Bota et al., 78869 "here the intensity measure isepressed in terms of G:. : continuous damage;continuous intensity model is theetrini model, "here G: is correlated "ith the relative economic cost, ranging fro 8to 0. %ther eamples of intensity measures used in vulnerability models are GH,:rias intensity +Sabetta et al., 01129, spectral accelerations +Goretti et al., 78869,spectral displacements +*alvi, 0111, *ro"ley et al., 78849, etc.
Damage is usual considered as a scalar quantity (that is damage to the "holestructure, damage tothe vertical bearing structure, etc.. )n some analysis the damage is considered avectorial quantity (damage to structural components and damage to non structuralcomponents. )n this case, each quantity is usually derived independently from theother. )n some cases, a &oint probability function has been proposed to represent thebuilding vulnerability, although this complicates considerably the analysis. )n somecases even the secondary vulnerability has been epressed in term of a damage
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vector, providing the building unusability probability given the su!ered structuraland non structural damage +Di asquale and Goretti, 78809.
Becently a Macroseismic method has been derived +Fagomarsino andGiovinazzi, 78869 from the de$nitions provided by the <MS;12 macroseismic scale.
The method provides DM=s for building types, translating the de$nitions providedby the <MS;12 scale to identify the intensity degree from the damage su!ered by
buildings. This has been done by the use of the Euzzy Set Theory and of therobability Theory. The model has the positive feature of providing a uniqueapproach suitable for all <uropean regions, ho"ever it enforces the building types tobehave according to the <MS12 scale and often this has been proved not to be thecase +Ma!ei et al., 78869.
)n conclusion since vulnerability deals "ith the problem of predicting the realdamage to structural and non structural components in many building types "hena!ected by an increasing intensity measures, it is inevitably an argument still openfor research. >hat is reputed necessary in applications is that the parameters usedto epress hazard should be suitable for an eJcient building responserepresentation and that the number of the building type information should beconsistent "ith the model accuracy and "ith the resources needed to collect data.
References
:T*, 0123 <arthquake Damage <valuation Data for *alifornia :pplied Technology*ouncil report :T*;0@ Bed"ood (*:
Araga, E., Dolce, M. and Fiberatore, D., (0127, : statistical Study on DamagedAuildings and <nsuingBe;vie" of the MS;?6 Scale, roc. H))) <uropean *onference on <arthquake<ngineering, :thens,September 0127.
*alvi, G.M. (0111, : displacement;based approach for vulnerability evaluation of classes of buildings,
Kournal of <arthquake <ngineering, Hol. @, -o. @, pp. 400;4@2.
*alvi, G.M., inho, B., Magenes, G.,Aomber, K. K., Bestrepo;Helez, F.E. and *ro"ley, '.,(7886, TheDevelopment of Seismic Hulnerability :ssessment Methodologies %ver the ast @8
Lears, )S<T Kournal of <arthquake Technology, Hol. 4@, -o. @.
*oburn, :. and Spence, B., (7887, <arthquake rotection (Second <dition, Kohn>iley and Sons Ftd.,*hichester, <ngland.
*orsanego, :. and etrini, H., (0114, <valuation criteria of seismic vulnerability of the eisting buildingpatrimony on the national territory, )ngegneria Sismica, atron ed., Hol. 0, pp. 06;74.
*osenza, <., Manfredi, G., olese, M. and Herderame, G.M., (7883, : multi;levelapproach to the
8/9/2019 8.Mauro Dolce Vulnerability x
http://slidepdf.com/reader/full/8mauro-dolce-vulnerability-x 5/6
capacity assessment of eisting B* buildings, Kournal of <arthquake <ngineering, Hol.1, -o.0, pp. 0;77.
*ro"ley, '., inho, B. and Aommer, K.K., (7884, : probabilistic displacement;basedvulnerability
assessment procedure for earthquake loss estimation, Aulletin of <arthquake<ngineering, Hol. 7,-o.7, 0?@;701.
Di asquale, G. and Goretti, :., (7880, HulnerabilitN <conomica e Eunzionale degli<di$ci Besidenziali*olpiti dai Becenti <venti Sismici )talianiO, I *ongresso -azionale OFP)ngegneriaSismica in )taliaO,otenza;Matera, 1;0@ September.
Di asquale, G., Goretti, :., Dolce, M. and Martinelli :., (7880, *onfronto fradi!erenti modelli di
vulnerabilitN degli edi$ci, I *ongresso -azionale QF=ingegneria Sismica in )talia,otenza;Matera,1;0@ September.
Dolce, M., Ruccaro, G., appos, :. and *oburn, :., (0114, Beport of the <:<<>orking Group @#Hulnerability and risk analysis, roc. I <uropean *onference on <arthquake<ngineering, Hienna,Hol. 4, pp. @841;@8??.
Dolce, M., (0116, Seismic vulnerability evaluation and damage scenarios, S;)talian>orkshop on
Seismic <valuation and Betro$t, December 07;0@, 0116 *olumbia niversity, -e" Lork *ity.
Goretti, :., Di asquale, G. and Giordano, E., (7886, Fa HulnerabilitN Sismica degli<di$ci Besidenziali#Becenti roposte del SS-, rogetto Beluis Finea 08, >orkshop su HulnerabilitNdell=<dilizia%rdinaria, Genoa, 00 Kuly
Goretti, :., -aso, G., Giordano, E., Hulcano, :. and Mazza, E., (788?, Scenari Sismicia Scala rbana. )rimi Bisultati del rogetto *rotone, I)) *ongresso -azionale QF=ingegneria Sismica in
)talia, isa,08;04 Kune.
Grant, D., Aomber, K.K., inho, K., *alvi G.M., Goretti, :. and Meroni, E., (788?, :rioritization Schemefor Seismic )ntervention in School Auildings in )taly, <arthquake Spectra, Holume 7@,)ssue 7, pp.710;@04
8/9/2019 8.Mauro Dolce Vulnerability x
http://slidepdf.com/reader/full/8mauro-dolce-vulnerability-x 6/6
Guagenti, <. and etrini, H., (0121, )l caso delle vecchie costruzioni#verso una nuovalegge danniintensitN, )H *onvegno -azionale QFP )ngegneria Sismica in )talia, Milano.
appos, :.K., itilakis, . and Stylianidis, .*., (0116, *ost;bene$t analysis for theseismic rehabilitation of buildings in Thessaloniki, based on a hybrid method of
vulnerability assessment, roc. of the 3th )nternational *onference on SeismicRonation, -ice, Erance, Hol. 0, pp. 486;40@.
Fagomarsino, S. and Giovinazzi, S., (7886, Macroseismic and Mechanical Models forthe Hulnerability:ssessment of *urrent Auildings, Aulletin of <arthquake <ngineering, Holume 4,-umber 4,-ovember 7886, Special )ssue QBisk < ro&ect Guest <ditors# B.Spence and A.FeArun
Ma!ei, K., Aazzurro, ., Marro", K. and Goretti, :., (7886, Becent )talian earthquakes#eamination of
structural vulnerability, damage and post;earthquake practices case studies andcomparisons to .S.practice, <arthquake <ngineering Besearch )nstitute.
Bossetto, T. and <lnashai, :., (788@, Derivation of vulnerability functions for<uropean;type B*structures based on observational data, <ngineering Structures, Hol. 73, pp. 0740;076@.
Bota, M., enna, :. and Strobbia, :., (7886, Typological fragility curves from )talianearthquake damagedata, roc. of the 0st <uropean *onference on <arthquake <ngineering and
Seismology, Geneva,paper no. @26.
Sabetta, E., Goretti, :. and Fucantoni, :., (0112, <mpirical fragility curves fromdamage surveys andestimated strong ground motion, roc. of the <leventh <uropean *onference on<arthquake<ngineering, aris.
-D/-)D%, (0123, ro&ect B<B/?1/803, ost;earthquake damage evaluation andStrength :ssessment of Auildings under Seismic *ondition, -D, Hienna, Hol. 4
>hitman, B. H., (01?@, Damage robability Matrices for rototype Auildings,Massachusetts )nstitute of
Technology, Department of *ivil <ngineering Besearch, Beport B?@;3?, *ambridge,Massachusetts.
