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Proceedings of the International ConferencePreventive and Planned Conservation
Monza, Mantova - 5-9 May 2014
Protezione dal rischio sismico
Proceedings of the International ConferencePreventive and Planned Conservation
Monza, Mantova - 5-9 May 2014
Comitato scientificoCarlo Blasi, Universita di Parma, ItalyFederico Bucci, Politecnico di Milano, ItalyFausto Cardoso Martinez, University of Cuenca, EcuadorAngelo Ciribini, Universita di Brescia, ItalyNigel Dann, University of the West of England, United KingdomStefano Della Torre, Politecnico di Milano, ItalySasa Dobricic, University of Nova Gorica, SloveniaXavier Greffe, Universite Paris 1 Pantheon-Sorbonne, FranceMassimo Montella, Universita di Macerata, ItalyElena Mussinelli, Politecnico di Milano, ItalyChristian Ost, ICHEC Brussels Management School, BelgiumAna Pereira Roders, University of Eindhoven, HollandPietro Petraroia, Eupolis Lombardia, ItalyMario Santana Quintero, Carleton University, CanadaKoenraad Van Balen, UNESCO Chair for PRECOMOS, KU Leuven, Belgium Minja Yang, RLICC, KU Leuven, BelgiumRossella Moioli, Distretto Culturale Monza e Brianza, Italy (coordinamento)
Segreteria scientifica del convegno:Maria Paola Borgarino, Stefania BossiPolitecnico di Milano, Dipartimento ABC - Architecture, Built Environment and Construction Engineering
Atti a cura di Stefano Della TorreCuratela editoriale: Maria Paola BorgarinoImpaginazione e collaborazione alla revisione dei testi: Cristina Boniotti
Politecnico di Milano - Dipartimento ABC - Architecture, Built Environment and Construction EngineeringFondazione Cariplo, progetto Distretti CulturaliDistretto Culturale Evoluto di Monza e Brianza - Provincia di Monza e della BrianzaDistretto Culturale Le Regge dei Gonzaga
Con il patrocinio della
@ 2014 Politecnico di Milano e Nardini EditoreTutti i diritti sono riservati
Copertina Ennio Bazzoni
Stampato per Nardini Editore
Le immagini contenute in questo volume sono fornite dagli autori alPolitecnico di Milano e all’editore sotto la propria esclusiva responsabilitàe sono state utilizzate per scopo didattico e per divulgazione.L’editore è disponibile a riconoscere la paternità delle immagini ad altriche la dimostrino, e a citare gli aventi diritto nelle successive edizioni.
NARDINI EDITORE
Proceedings of the International ConferencePreventive and Planned Conservation
Monza, Mantova - 5-9 May 2014
A cura di Stefano Della TorreCuratela editoriale Maria Paola Borgarino
3
Protezione
dal rischio sismico
Indice
LA PROTEZIONE DAL RISCHIO SISMICO A LIVELLO TERRITORIALE: UNA STRATEGIADI PREVENZIONE POSSIBILE, TRA ECONOMIA E RESPONSABILITÀCarlo Blasi, Federica Ottoni, Eva Coisson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pag. 1
CRITICITÀ DEL PATRIMONIO STORICO NELLE ZONE A BASSA SISMICITÀ - IL CASODI UNA VILLA VENETA SETTECENTESCAMarco Boscolo Bielo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 13
PRESIDI STATICI ED OPERE DI MESSA IN SICUREZZA NEI SITI ARCHEOLOGICI:CONFINI E LIMITI DEL PIANO DI MANUTENZIONE PROGRAMMATANicola Santopuoli, Miriam Vitale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 27
RETROFITTING OF MASONRY STRUCTURES WITH COMPOSITE MATERIALS.EXPERIMENTAL AND NUMERICAL RESULTSGaia Barbieri, Massimiliano Bocciarelli, Lorenzo Borrello, Sara Cattaneo . . . . . . . . . . . . . . . . . . . . . . . . ” 37
KNOWLEDGE LEVELS AND CONFIDENCE FACTORS: CONSIDERATIONS ON THEIREFFECTIVENESSMarco Magnani . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 49
PER UNA CONSERVAZIONE PREVENTIVA. LA CHIESA DELL’IMMACOLATAA PIZZOFALCONE A NAPOLI TRA ISTANZE DI CONSERVAZIONE E PROTEZIONEDAL RISCHIO SISMICORenata Picone, Andrea Prota, Arianna Spinosa, Luigi Veronese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 61
POST SEISMIC STRATEGIES AFTER 2012 EARTHQUAKES ON MILITARY ARCHITECTUREIN MANTUA AREA Antonella Saisi, Stefania Terenzoni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 73
RISK ASSESSMENT AND PREVENTION PRIORITIES IN CULTURAL HERITAGE PRESERVATIONAndrea Dall’Asta, Manuela Battipaglia, Federico Bellini, Tamara Carducci, Graziano Leoni,Giuseppe Losco, Alessandra Meschini, Enrica Petrucci, Quintilio Piattoni, Daniele Rossi,Filippo Sicuranza, Horst Thaler, Enrico Tubaldi, Alessandro Zona . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 85
DURABILITY OF FIBER REINFORCED SYSTEMS FOR SEISMIC RETROFITTINGOF MASONRY STRUCTURESElisa Bertolesi, Francesca Giulia Carozzi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 97
CENTRI STORICI, VULNERABILITÁ, RISCHIO E GESTIONE DELLA CONSERVAZIONE.UNA PROPOSTA D’IMPLEMENTAZIONE DELLO STRUMENTO ‘CARTA DEL RISCHIO’Carlo Cacace, Donatella Fiorani . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 107
CARTA DEL RISCHIO DEL PATRIMONIO CULTURALE: STUDIO SULLA VULNERABILITÀE PERICOLOSITÀ SISMICA DEL PATRIMONIO CULTURALE IN SICILIA E CALABRIACarlo Cacace, Adalgisa Donatelli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 119
PROTEZIONE SISMICA PREVENTIVA. DALLA STORIA AL RESTAURO SISMICOATTRAVERSO L’ISOLAMENTO SISMICO ALLA BASEAbdul Kader Moussalli, Francesco Amendolagine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 129
STRATEGIES FOR SEISMIC RISK PROTECTION. A MULTI-DISCIPLINARYMETHODOLOGICAL APPROACH FOR HISTORICAL CITY PATTERNSCristina Boido, Monica Naretto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 143
PROCEDURE PER LA MESSA IN SICUREZZA DEL PATRIMONIO MOBILE IN CASODI CALAMITÀ NATURALI. DA CELANO A SASSUOLO, DA MODELLO A STANDARDFrancesca Capanna, Paolo Scarpitti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 153
SEISMIC PROTECTION OF EXISTING BUILDINGS IN THE ITALIAN EXPERIENCEMaria Adelaide Parisi, Chiara Tardini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ” 165
segue Indice
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DURABILITY OF FIBER REINFORCED SYSTEMS FOR SEISMIC RETROFITTING OF MASONRY STRUCTURES
Elisa Bertolesi, Francesca Giulia Carozzi
Politecnico di Milano, Department of Architecture, Built Environment and Construction
Engineering
Abstract
Last seismic events showed the necessity to develop activities of protection
of the cultural and architectural heritage, with a complete evaluation of the
seismic vulnerability, comprising a deep knowledge of architecture and retrofit-
ting techniques.
“La strada da percorrere è presto indicata: bisogna innanzitutto conoscere
«cosa» conservare, e da tale conoscenza far scaturire il «come» conservare con
sicurezza” (Giuffrè, 1993). The aim is to choose the best solutions in order to
propose a not invasive intervention, with a correct equilibrium between the
necessity of structural retrofitting and the conservation of architectural heritage.
An important item is the use of composite materials, that showed good
structural characteristics but that were often applied without pay attention to
the specific characteristics of each historical building. An example can be the
retrofitting with fiber composite materials (FRP), that in the last years were
often applied on historical masonry architectures. The aim of this work is to
study an alternative retrofitting system that involves the use of fiber reinforced
materials applied with an inorganic matrix (FRCM). A critical comparison be-
tween these two techniques is proposed, the suggested system showed good
compatibility with the existing structures, a better reversibility and durability,
and it ensured the necessary mechanical properties.
The built heritage in Italy and Europe mainly consist of masonry structures.
Most of the historic constructions suffer a lack of adequacy from a structural
point of view. The preservation of the architectural heritage presents one of the
most important challenges in civil engineering due to the complexity of the
geometry of the structures, the variability of the materials used and the loading
history of the buildings. In Italy, this objective has increased for existing con-
structions due to high seismic risk (Fig. 1 shows a failure mode of a masonry
walls after the seismic event of L’Aquila in 2009). The great variety of the mate-
rials and the building techniques used make the study of masonry a very com-
plex field that require more detailed experimental and numerical investigations,
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concerning the behavior of masonry structure but also referred to the mechani-
cal characterization of materials used. As Anzani et al. (Anzani et al., 2009)
remarked on one hand the conservation of the pre-existing heritage gains an
increasing relevance toward the safeguard of the memory and the complex
relationship that the architectural culture has to carry out with its past. The
masonry substrate, despite concrete ones, became very interesting for engineer-
ing study in Italy after the recent earthquake disasters (Brandonisio et al., 2013).
More detailed experimental investigations are required to fill the lack of
knowledge referring to their mechanical behavior and concerning the influence
of retrofitting strengthening in the behavior of masonry. In the recent years a
lot of experimental tests on some retrofitting techniques were performed to
verify the efficiency of these repairs on new and existing structures.
This work analyses the characteristic of two alternative types of reinforced
composite materials. In particular the problems of durability and reversibility is
investigated with a literature review and an experimental experience developed
at the Politecnico di Milano.
Fiber reinforced systems: FRP and FRCM
One of the most attractive type of strengthening is the use of Fiber Rein-
forced Polymer material (FRP), which are made up of fibers embedded with
epoxy resins. Such materials become very popular in the last decade due to
their advantages: reduced mass, durability, ability to mould complex forms but
also their high mechanical characteristic such as elastic modulus and strength.
Their advantages were also referred to their lightweight that permit, unlike
other traditional strengthening techniques, not to increase the self-weight of the
element strengthened. This advance means that the seismic response of the
reinforced structure remain unchanged (Saileysh Sivaraja et al., 2013). The
lightweight of the FRP make this strengthening faster, easier and not dangerous
for the operator. On the other hand FRP materials are affected of some draw-
backs, for instance low vapour permeability, poor behavior at elevated tempera-
tures, incompatibility of resins on different substrate materials, relative high
cost of epoxy resins, no reversibility of the installation.
Before to study a retrofitting intervention it’s important take into account
many parameters such as different materials, textures, environmental conditions
and mechanical behavior of the substrate. One of the most important topics
developed in these years were the compatibility of strengthening techniques
with the cultural and historical buildings, in particular with the nature and the
peculiarities of the materials used, the aim is to prefer high efficient strengthen-
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ing techniques but low invasive. An important subject, still object of study, is
the compatibility and reversibility of FRP material with masonry substrate. The
interest on these themes is referred to the main failure mode that is experienced
with FRP strengthening, it is called “debonding failure” and it is due to a loss
of bond between the substrate and the FRP reinforcement. Since the substrate
is usually weaker, the reinforcement failure is normally associated with the
removal of a thin material layer (Fig. 2 shows an experimental experience of a
collapse of FRP retrofitting system). A wide range of experimental results and
also numerical modelling are avaible in literature for concrete substrate, despite
masonry ones. Some investigations were conducted on the bond developed
between FRP and different masonry substrate (Carrara et al., 2013).
An alternative to these techniques were the Fabric Reinforcement
Cementitious Matrix materials (FRCM). These type of retrofitting substituted
the epoxy resins with an inorganic matrix, mainly a cement based mortar with
short fiber inside. In recent years the attention to these type of innovative ma-
terials grow, a lot of different reinforcement techniques were created: short
fibers (FRC, Fiber Reinforced Concrete) and continuous fibers in a fabric form
(TRC, Textile Reinforced Concrete) were used mainly to produced cladding
panels, exterior sidings, shells, roofing or flooring tiles. FRCM are a particular
type of TRC in which the fibers used are non-impregnated and the matrix is
inorganic.
FRCM materials are used as alternative of FRPs in the strengthening of ex-
isting structure, mainly masonry, because of their compatibility with traditional
materials. Other important advantages of FRCM materials are: water vapour
permeability which makes it compatible to be applied on masonry, no special
equipment specialised operator are required, easy to manipulate, it is applicable
over irregular surfaces without the need of a specific treatment, it is fire re-
sistant. On the other hand, FRCM composites have some drawbacks, as for
instance the lower levels of adhesion between the yarns and the matrix. The
bond influenced the behavior of the reinforcement, also referring to the adhe-
sion between different type of rovings and the cementitious matrix. The typical
stress-strain behavior of a FRCM is a tri-linear curve, with a first elastic phase, a
second phase where the cracks in the mortar start to grow, and a last phase in
which the mortar is fully cracked and the textile were subjected to the tensile
load (Hartig et al., 2008). The failure mode is characterised a by a cracking of
the matrix and collapse of the textile without the removal of a layer of the sub-
strate (Fig.3 shows a experimental experience of a collapse of FRCM retrofit-
ting system).
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The paper presented a comparison between FRP and FRCM materials. A
state of the art of some FRP structural applications and drawbacks of these
materials is proposed, with particular attention on their application on monu-
mental heritage. The theme of durability is also investigated with attention on
different types of environmental conditions. A comparison between the behav-
ior of treated specimens reinforced with FRP and FRCM is presented.
Durability of FRP systems
Effectiveness of composite materials as FRP used in architectural and engi-
neering works is strongly dependent on bond in the interface with the support.
The most common environmental factors which a structure is exposed to dur-
ing its service life are moisture and temperature variation (Colombi, 2010), and
alkaline and acidic environments. It is well known that salt crystallization is one
of the most frequent causes of surface damage of masonry in aggressive envi-
ronments. Binda et al (Binda et al., 2011) developed an experimental analysis in
order to study the durability of brick masonry reinforced by CFRP to salt crys-
tallization. FRP strips were applied on masonry elements and tested in presence
of a sodium sulphate solution. The tests simulated an aggressive environment
in which salts can arrive into the masonry by capillary rise. The experimental
campaign included the crystallization tests on masonry assemblages, the damage
measurement with a laser profilometer, the bond investigation by thermogra-
phy which allows to check the connection between the FRP and the substrate.
The damage caused by the salts seem to be higher on the masonry when re-
paired with this technique than on the blank specimens, due to higher accumu-
lation of humidity and salts around the strips and within them; the salts crystal-
lize as cryptoflorescence underneath the depth of penetration of the primal and
within the strip itself causing delamination and detachment of the strip.
Briccoli Bati and Rotunno (Briccoli Bati et al., 2001) studied the environ-
mental resistance and durability of the bond between the masonry substrate
and the CFRP composite. They subjected a lot of specimens on alternating
cycles of wet-dry and freeze-thaw, and then carried out mechanical shear tests.
They could observed that exposure to alternating wet-dry has proved to have
only a light effect on the mechanical behaviour of the specimens tested; instead
the cyclic of freezing-thawing brought a detachment of the composite CFRP
material form the masonry, completely nullifying the reinforcement operation.
Also Valluzzi et al. (Valluzzi et al., 2011) carried out tests on masonry brick
and CFRP subjected to thermal cycle of freezing and thawing. They could ob-
served a clear penetration of the primer into the brick (1-2 mm), instead the
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deeper part not impregnated remained porous and weak, and here the delami-
nation occurred. The reason could be connected to the fusion temperature of
the epoxy resin or to the differential deformation of the epoxy penetrated into
the brick. Ghiassi et al. (Ghiassi et al., 2013) investigated the effect of water on
the bond behavior in FRP-strengthened masonry elements. Clay bricks were
strengthened with FRP and immersed in water for 24 weeks after complete
curing. The bond degradation due to moisture exposure is investigated by per-
forming pull-off and shear tests. The results show a significant reduction of
mechanical characteristics of epoxy resin (young’s modulus and tensile
strength), the pull-off bond strength has been reduced 56% after 24 weeks of
immersion, however the failure mode remained cohesive in all immersion peri-
ods, with a reduction of the thickness of the detached brick layer. Most im-
portant results of shear bond tests is the increase of effective bond length. The
effective bond length is defined as the minimum length along which the strains
and stresses are transferred to the substrate, changes in effective bond length
due to water immersion can cause unsatisfactory failure modes in the strength-
ened specimens.
Durability of FRCM systems
The substitution of FRP with fibre-reinforced mortars would be inhibited
by the relatively poor bond conditions in the resulting cementitious composite
as, due to the granularity of the mortar, penetration and impregnation of fibres
textile is very difficult to achieve. The external filaments are in direct contact
with matrix and tightly bonded, instead the filaments in the core presents a
poor contact with matrix, and easily slip at low friction.
In order to ensure a good application of the FRCM, the following require-
ments should be met: no shrinkage; high workability; high viscosity (application
should not be problematic on vertical or overhead surfaces); low rate of worka-
bility loss (application of each mortar layer should be possible while the previ-
ous one is still in a fresh state). In case glass fibers grid or textile are used, the
cement-based matrix should be of low alkalinity.
Possible negative alterations must be known in order to be considered in
the design of retrofitting with FRCM materials. Changes in the mechanical
performance of the composite can basically result from deterioration of the
fibres, alterations in the matrix itself, and changes in the bond between matrix
and fibres.
The ageing of FRCM made of alkali-resistant glass yarns or textile and of a
cement-based matrix could be subjected to the following degradation process
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(Butler et al., 2010): corrosion of the filaments made of glass caused by alkaline
attack of OH-ions in the pore solution; delayed failure of the AR glass fila-
ments under sustained load in the highly alkaline concrete due to under critical
growth of surface flaws; and enhancement of the bond between filaments and
matrix with continued hydration and precipitation of hydration products in the
interface between filaments and matrix as well as in empty spaces between the
filaments of multi-filament yarn. Furthermore, the resistance of the concrete
matrix itself to environmental stresses such as frost or chemical attack can
affect the composite durability in similar fashion.
Micro surface defects caused by the glass filament spinning process or by
chemical attack reduce significantly the strenght of glass filaments.
Barhum et al. (Barhum et al., 2009) studied the transport of water and gases
in TRC made with different types of biaxial textile of AR glass and a
cementitious mortar. In order to measure water absorption, the lower surface
of each specimen was immersed in water for 72 hours, the tests were per-
formed on two types of specimens, one with and one without textile rein-
forcement. The results of the tests showed that due to the capillary action of
the multifilament yarns, the specimens with layers of textile absorbed water
much fast than the specimens without textile reinforcement.
Durability of FRP and FRCM systems: experimental experience de-
veloped at the Politecnico di Milano
In literature there are some works that analyzed the durability of single el-
ements that compose an FRCM material, but there aren’t a lot of studies that
investigated the durability of those materials applied on a masonry substrate. A
first approach could be represented by a series of experimental tests developed
by the authors.
Experimental pull-off and shear push-pull double lap tests were performed
on specimens realized with different types of reinforcement bonded to the two
sides of a single clay brick. Three different types of reinforcement were investi-
gated: two types of FRCM with a glass fiber grid (one with base cementitious
mortar and one with lime based mortar) and a FRP with carbon textile and an
epoxy resin. The specimens were subjected to alternating cycles of freeze and
thaw (21 cold cycles of 20 °C 90% UR for 30 min _ -20 °C for 1h _ 20 °C 90%
UR for 30 min; 21 hot cycles of 20 °C 80% UR for 30 min _ 60 °C 80% UR
for 30 min _ 20 °C 80% UR for 30 min).
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The results showed for the FRP materials (Fig. 4a), an evident decrease of
the pull-off resistance of 25% and of the shear strength of 29%. In the pull-off
tests the failure was at the interface between carbon textile and epoxy resin.
The analysis were more complicated for the FRCM samples. The test on
specimens with lime based mortar (Fig. 4b) showed a little increase (11%) in
the pull-off resistance and an evident increase (78%) in the shear bond
strength. The causes of this behavior must be investigated more thoroughly, a
first observation could be that the samples subjected to the cycles had an age of
2 months, instead the control specimens of 28 days only.
For FRCM specimens with cementitious mortar (Fig. 4c) the analysis of the
results was more complex, in the pull-off test there was a decrease of the 57%,
instead the results of shear test show an increase of 22%.
A new experimental campaign will be developed to study these problems.
Conclusions
This work deepened the use of innovative techniques and materials to ret-
rofit masonry structures (FRP and FRCM). The strengthening techniques pro-
posed showed good structural characteristics. They were often applied without
pay attention to the specific characteristics of each historical building, to the
relation between the reinforcement and to the substrate and the influence of
the retrofitting in the conservation of the cultural heritage from an esthetical
and structural point of view. In this work an alternative retrofitting system that
could replace the use of FRP is presented. In particular the durability of two
techniques is investigated, the FRCM system shows a better reversibility and
durability and ensures the necessary mechanical properties in the retrofitting of
historical structures. FRCMs involve the use of cementitious or lime based
mortars. Obviously the first one presents better mechanical properties but the
second one shows a better compatibility with ancient masonry structures. The
best solution should be the study of an ad hoc reinforced material for each
structures. This solution shall take into account different items: the mechanical
and physical characteristics of the structures, the function, the preservation of
the structure, the materials, the shape, the changes that the passing of time had
developed on the architecture. An important limit in the use of FRCM systems
is the difficult in designing an ad hoc retrofitting intervention, and the impossi-
bility of use of these materials on brick walls without plaster or painted walls.
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Anzani A., Binda L., Garavaglia E. (2009), Long-term damage of historic
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gases in crack-free and cracked textile reinforced concrete. Concrete repair, rehabil-
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Binda L., Tedeschi T., Valluzzi M. R., Garbin E., Panizza M. (2011), Salt
crystallization tests on brick masonry reinforced by CFRP textiles. XII DBMC.
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Butler M., Machtcherine V., Hempel S., (2010), Durability of textile rein-
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Fig. 1 - A failure mode of a masonry walls after the seismic event of L’Aquila in 2009.
Fig. 2 - An experimental experience of a collapse of FRP retrofitting system.
Fig. 3 - A experimental experience of a collapse of FRCM retrofitting system.
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Fig. 4a
Fig. 4b
Fig. 4c
