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SWrucWural Analysis of HisWorical ConsWrucWions – Jerzy Jasieńko (ed) © 2012 DPNH ProcławH PolandH ISSN 0860-2395H ISBN 978-83-7125-216-7

Teb efpTlofCAi CbNTob lc mlddfl mfCbNZb AcTbo i’AnrfiA bAoTenrAhbW BbeAsflro ANa pTobNdTebNfNd lc MAplNoY AddobdATb tAiip cormisano AntonioNI conti oobertaOI Mazzolani cederico MKP ABpToACT moggio micenze EAbruzzi regionI ftalyF was one of the most damaged small towns during i’Aquila earthquake. fn particularI its historical centre was strongly hit by this catastrophic event due to different seismic vulnerabilities which have been investigated and discussed in the current paper. fn the framework of this activity some case studies were carefully chosen and examined in relation to several chief featuresI such as soilI exposure and masonry setting. qhe main aim of the study was to both identify and assess old masonry morphological characteristicsI by comparing them with literature referencesI aiming at both fully understanding their response and implementing an effective and sustainable strategy of retrofitting interventions. aetected masonry features made difficult the damage analysis and the subsequent consolidation approaches to be used. fn factI no ordinary settingI small size stones having irregular shape and assembled with large parts of mortarI no regular flatten stone alignment and no transversal connection elements were recognised. After thatI different masonry failures due to three main seismic vulnerabilities of buildings placed in the moggio micenze were illustrated. After the identification of these collapsesI the singular weak elements of damaged block masonry units were exhaustively identified and analysed with the final aim to design a useful retrofitting intervention. heywordsW eistorical centresI Building aggregatesI Masonry apparatusI eeadersI

ooof maintenance and state NK fNTolarCTflN qhe urban tissue of moggio micenze is composed of old masonry constructionsI which represent the major part of the builtJup. qhey were erected in aggregate condition following two different joint methodsW the oldest constructions are placed around the peak of the hillI following the territory topographyI whereas the youngest ones are located on both sides of the main street Epee cig NF. As a consequenceI the wide spread housing typology is a construction composed by two differ levels in sequence overlapping a basement. qhis schemeI which is helpful for drop overcomingI is really vulnerable towards seismic actionsI with often produce outJofJplane collapse mechanisms Esee cig. OF.

N aepartment of ptructural bngineeringI rniversity of kaples “cederico ff”I antoform]unina.it O aepartment of ptructural bngineeringI rniversity of kaples “cederico ff”I roberta.fonti]unina.it P aepartment of ptructural bngineeringI rniversity of kaples “cederico ff”I fmm]unina.it

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cigK N qhe Abruzzo region Ein green on the leftF within the ftalian meninsula and the moggio micenze map Ethe historical centre placed on the peak is marked in redF

cigK O A typical housingJtypology scheme belonging to the historical peak area of moggio micenze after i’Aquila earthquake

OK Teb pbfpMfC sriNboABfTfbp

OKNK denerality tith reference to the moggio micenze builtJup like representative case of the constructive practice of the Abruzzo townsI three primary seismic vulnerabilities have been detectedW

– the ground response; – structural alteration and maintenanceI with particular attention to roof changing in terms of both

geometrical scheme and materials; – masonry apparatus.

fn this paper the last two vulnerabilities have been considered and discussed. OKOK ptatic problemsW roof alteration and maintenance After the earthquake it was noticed that constructions often failed due to either lack in maintenance of roofs or change of the coverage layers. fn particularI information deriving from the knowledge of the original roof configuration showed that timber ties are generally hooked up by anchors to top panels outside Ecig. PF.

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cigK P i’Aquila old buildingsW ooofJtypology scheme xNz

qhis valuable roof scheme was often replaced by dissimilar coveringsI no effective during earthquake. As a consequenceI four different roof conditions were noticed within the investigated cityI they being classified into the following four categoriesW

AF lriginal roof scheme with no maintenance operations. ioosing of the original static capacity. BF ooof structural configuration change. jaterials and pitches slope are similar to the existing ones

but different engineering details Eabsence of anchorsF are noticed. CF ooof alteration with material variation. aF ooof pitch slope changing or roof scheme totally divergent from the original one.

qhese roof typologies are shown in cigures from Q to TI where a case study representative of each of the four categories is illustrated.

cigK Q bxample of original roof configuration with no effective restraint capacity Ecategory AF

EaF EbF

cigK R jasonry construction suffering outJofJplane collapse due to the top anchors absenceW frontal EaF and back EbF views Ecategory BF

qimber anchor

qie rod

qimber corbel murlin

jasonry top panel

mlanking

ooof tile ptrut

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cigK S qhe roof material changeW no collaboration between masonry walls and rigid coverage Ecategory CF

cigK T Changing of the roof pitch slope and type is responsible of the upper masonry wall collapse Ecategory aF

OKPK The masonry apparatus qhe collapse mechanism derived from alteration of the original roof scheme Ecategory aF is directly related to the masonry apparatus quality. fn i’Aquila area the main masonry typologies are subdivided in two categories xOzW NF qhe first masonry type is widespread within i’Aquila city and no in the neighborhood. qhe

constructive scheme is based on stones having small size and irregular shape and assembled with no ordinary setting. As a direct consequenceI total absence of headers is noticed and lack among either stones or within thickness mortar joints can be pointed out. pometimes the stone irregularity is filled up by wedges elements. oegular flatten made in bricks and stretcher elements are present. qhis masonry typeI which experienced a local mechanism under form of outJofJplane rigid block behaviourI is shown in cigure U.

EaF EbF cigK U A typical masonry panel detected in i’Aquila historical centre EaF and a first category masonry

sample ENm × NmF EbF

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OF qhe second type is instead typical of the constructions within towns surrounding i’Aquila. qhis masonry apparatus is based on small size stones with no transversal section linksI no stretcher elementsI no bricks layers and no sufficient wedges elements Esee cig. VF. qhereforeI due to the above lacksI a failure of the wall external layers occurs because of buckling phenomena.

EaF EbF

cigK V A masonry panel detected in i’Aquila surrounding area and a second category masonry sample ENm × NmF EbF

qhe masonry constructions of the urban tissue of moggio micenze match the second category Esee cig. VF; this mind that no rigid block behaviour can be expected during earthquake. fn cigure NM the failure due to buckling phenomena of the portion of a masonry panel not restrained by tie beams is shown.

cigK NM jasonry failure due to the wrong assembling of masonry stones. poI the illustrated deficiencies must be eliminated in order to guarantee a better seismic behaviour of the study masonry walls. keverthelessI the better strengthening approach detection is really difficult. fn order to define an effective and sustainable strategy of interventionI strictly connected to this masonry typologyI a destructive inJsitu experimental campaign on fullJscale structural walls belonging to an existing building was plannedI it being conducted from the rniversity of kaples “cederico ff” in collaboration with the rniversity of oeggio Calabria Ecoordinator jichele CandelaFI the rniversity of merugia Ecoordinator Antonio BorriF and the rniversity of denova Ecoordinator pergio iagomarsinoF xPJSz. qhis experimental research project was developed with the collaboration of the junicipality of i’Aquila. qhe test campaign was directed both to the identification of i’Aquila masonry panel mechanical parameters and to the behavioural assessment of panels under both dynamic and static conditions. fn particularI static tests were performed to recognise the masonry collapse behaviour Ein plane failure or outJofJplane oneF. fnsteadI outJofJplane tests were carried out under both “displacementJcontrol”I with the possibility to apply displacements having alternate directionsI and “forceJcontrol”.

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PK A pTobNdTebNfNd MbTela clo MAplNoY tAiip

PKNK The proposed idea ptarting from the identification of masonry panel failure due to two principal defectsI that is absence of transversal connection elements EheadersF and no contact among stonesI the rniversity of kaples designed a traditional reinforcement strategy based on both placement of timber headers within the masonry thickness and replacement of mortar joints with wedge elements. qhe starting point of the study was the analysis of the masonry setting and its comparison with the “rules of art” for masonry panels. iater onI the strengthening idea was born from Abruzzo local constructive practice for old masonry buildingsI where timber elements were widespread employed for connections of masonry walls. qhereforeI some timber headers were placed within the panel thickness in order to obtain the mechanical interlocks of the two panel layers. qo this purposeI the masonry setJup reading was important since the difference between the two panel faces allowed to define a unusual headers setting schemeI which is schematically illustrated in cigure NNa. qhe executive phases of the strengthening method foresaw the panel drilling with Q circular holes Ediameter of OMM mmF along the whole panel thicknessI the setting of wooden headers with the regular stress condition reJestablished by wooden wedge elements and the replacement of mortar joints with stone wedge elements Ecig. NNb and cF.

EaF EbF EcF

cigK NN mlacement scheme of timber headers within masonry panel EaFI executive phases EbF and detail of both timber header and stone wedge elements EcF

PKOK The out-of-plane test qhe panelI having width of O.NM mI height of Q.MM m and depth of M.SM mI was before cyclically tested by means of a hydraulic jack under “displacementJcontrol”I with the possibility to produce displacements in alternate directionsI and then pulled out with the same jack in the final test phase. qhe pushing action of the jackI placed at a height of O.OR mI was applied to the panel through a rigid box steel beam anchored to it by steel bars. qhe test setJup was arranged to take advantage of panel position in the building scheme Ecig. NOF.

cigK NO aetails of the test setJup

qhe data resulting from experimental testI referred to the hydraulic jack positionI are reported in qable NI where it is apparent that the maximum obtained force cmax corresponding to a displacement of M.OO m is NQSV dak. fn the table the pushing force is the load applied to the panel at the jack levelI

aisplacement transducer gack Box beam

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whereas jo is the overturning bending moment and js is the stabilizing bending moment. qhe achieved results were then compared to other results obtained from experimental tests on different panels Ewithout reinforcementI reinforced with concrete headersI reinforced with injectionsFI which presented both dissimilar geometrical dimensions and disparate jack application height. qo this purposeI the maximum forcesI and therefore the pushing actionsI attained by each panel was homogenised each other with reference to a N.MM m large masonry portion Esee cig. NPF.

Table N ptrengthened panel response compared to the rigid block behaviour

cmax EdakF

c homol EdakF

mushing force EdakF

jo EdakGmF

js EdakGmF

bfficiency compared to a rigid block response EjoLjsF

NQSV NSRP TUT NRTQ NRTM N

cigK NP Comparison among strengthened masonry panels By comparing the behaviour of the panel without reinforcement Eqable OF with the one strengthened by means of timber headersI it is possible to notice that performed intervention produces improvement in masonry mechanical interlock whichI together with the wedge elements influenceI allows to attain a total force four times more than the one of the original panel Esee cig. NPF. fn particularI the presence of stone wedge elements produce a strength increase two times than the one of the panel reinforced with headers only.

Table O rnreinforced panel response compared to the rigid block behaviour

cmax EdakF

c homol. EdakF

mushing force EdakF

jo EdakGmF

js EdakGmF

bfficiency compared to a rigid block response EjoLjsF

NTS OTT NSS OVM NPTP MKON

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QK ClNCirpflNp qhe performed study has allowed to individuate the seismic vulnerabilities affecting the behaviour of masonry constructions within the smallest historical centres in the district of i’Aquila. fn particularI the modification of building roof in terms of both constitutive materials and pitch slope and number represents one of the main failure cause. fn factI especially due to the lack of timber anchor able to make the roofJtop masonry panels connectionI many roofs collapsed under the recent i’Aquila earthquake. qhe occurred masonry wall failures has allowed to implement their strengthening strategies based on the use of both connections among masonry layers and stone wedge elements. qhese interventions are used to guarantee both vertical and horizontal mechanical interlocks of masonry according to the “rules of art”I which are not fulfilled in many cases. qhis means that for i’Aquila standard masonry there is a wall partI proportional to the gap noticed in the experimental response between the original panel and the strengthened oneI that during earthquake cannot be used to resist bending moment. ConsequentlyI the pushing action necessary for panel overturning is reducedI as confirmed by the results of the performed experimental activity. As a resultI the reinforcement intervention deleted the gap between i’Aquila strengthened masonry response and the theoretic one for rigidJblock. qhis gives us the significant information that it is really possible to reinforce into an effective way the i’Aquila old construction masonry. AChNltibadbMbNTp qhe authors acknowledge the partial financial contribution provided by ftalian ketwork of peismic iaboratories EoeirfpFI in the framework of the amC OMNMJOMNP mrojectI the i’Aquila junicipality and the following building firmsW qo.ai.ja. s.r.l.I a’Agostino Angelo Antonio Costruzioni denerali s.r.l. and deoJConsult s.r.l. obcbobNCbp xNz saragnoli C. EOMMUF ia Costruzione tradizionale in AbruzzoK conti materiali e tecniche

costruttive dalla fine del Medioevo all’lttocentoK dangemi. xOz conti o.I cormisano AI jazzolani c.j EOMNNF. iDedificato storico di moggio micenze EAnFWil caso

studio di un aggregato su pendio. fnW mrocK of the N4th ftalian ConfK on barthquake bngineering Akfafp OMNNK BariI NUJOO peptember OMNN.

xPz Borri A.I Candela j.I conti o. EOMNNF. cullJscale experimental test in the historical centre of i’Aquila – differently consolidated and outJofJplane loaded masonry panelsW first results” Ein ftalianF. fnW mrocK of the N4th ftalian ConfK on barthquake bngineering Akfafp OMNNK BariI NUJOO peptember OMNN.

xQz Borri A.I Candela j.I contiI o. EOMNOF. lld masonry structures in i’Aquila historical centreW etrofitting strategies and full scale tests. qhe assessments. fnW mrocK of NRth torld Conference on barthquake bnginneringI iisbonI OQ J OU peptember OMNO.

xRz Candela jI Cattari pI iagomarsino pI oossi jI conti o.I magliuca b EOMNNF. fn situ tests for inJplane response assessment of a masonry panel into a building in i’Aquila” Ein ftalianF. fnW mrocK of the N4th ftalian ConfK on barthquake bngineering Akfafp OMNNK BariI NUJOO peptember OMNN.

xSz Candela j.I Cattari p.I iagomarsino p.I oossi j.I conti o.I magliuca b. EOMNOF. fnJsitu test for the shear strength evaluation of masonryW the case of a building hit by i’Aquila earthquake EftalyF. fnW mrocK of NRth torld Conference on barthquake bnginneringI iisbonI OQJOU peptember OMNO.