PSI - Issue 29

Volume 2 9 • 2020

ISSN 2452-3216

ELSEVIER

Art Collections 2020, Safety Issue (ARCO 2020, SAFETY)

Guest Editors: Marco T anganelli Stefania Viti

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Art Collections 2020, Safety Issue (ARCO 2020, SAFETY) An experimental methodological approach aimed to preventive conservation and sustainable adaptive use of the cultural heritage rt ll ti , f t I ( , )

Carla Balocco a , Margherita Vicario b, *, Maurizio De Vita b a Department of Industrial Engineering University of Florence, via S. Marta 3, Florence 50139, Italy b Department of Architecture University of Florence, via della Mattonaia 14, Florence 50121, Italy Ca l l a , it i i b, , i i it b a epart ent of Industrial ngineering niversity of lorence, via S. arta 3, lorence 50139, Italy b epart ent of rchitecture niversity of lorence, via della attonaia 14, lorence 50121, Italy

Abstract str ct

© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti Microclimatic conditions play a key role in the conservation of art collections and architecture, results obtained by monitoring campaign are essential to define preventive conservation strategies. An experimental methodological approach was identified to analyze the microclimatic conditions, to evaluate environmental damage and decay phenomena and support the conservation of artworks. Results obtained from experimental measurements performed inside a historical Dominican convent , which is now the San Marco museum in Florence (Italy), were compared and discussed. The detailed investigation of thermo -physical and thermo hygrometric behavior of building in response to internal and external stress, allows to define preventive conservation strategies and plant solutions in a perspective of its acclimatization and adaptive reuse of internal ambient. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti Keywords: microclimate monitoring; non-invasive measurements; cultural heritage; adaptive reuse; sustainability; acclimatization solutions 1. Introduction The goods that make up the cultural heritage are very varied and complex, so much so that the research activity currently carried out on deteriorationprocesses has not yet led to univocal and conclusive results. Today, there is no single and unique protocol internationally accepted: there are guidelines and recommendations (UNI 10829 (1999); MiBAC (2001); EN15757 (2010);ASHRAE (2011)) a imed at establishing the basic criteria and providing indications icr cli atic c iti s la a e r le i t e c ser ati f art c llecti s a arc itect re, res lts tai e it ri ca ai are esse tial t efi e re e ti e c ser ati strate ies. e eri e tal et l ical a r ac as i e tifie t a al ze t e icr cli atic c iti s, t e al ate e ir e tal a a e a eca e e a a s rt t e c ser ati f art r s. es lts tai e fr e eri e tal eas re e ts erf r e i si e a ist rical i ica c e t , ic is t e a arc se i l re ce (Ital ), ere c are a isc sse . e etaile i esti ati f t er - sical a t er - r etric e a i r f il i i res se t i ter al a e ter al stress, all s t efi e re e ti e c ser ati strate ies a la t s l ti s i a ers ecti e f its accli atizati a a a ti e re se f i ter al a ie t. 2020 e t rs. lis e lse ier . . This is an open access article un er t e - - license (http://creativecommons. r /lice ses/ - c- / . /) eer-re ie er res si ilit f arc a a elli a tefa ia iti ey ords: icrocli ate onitoring; non-invasive easure ents; cultural heritage; adaptive reuse; sustainability; accli atization solutions . I t ti s t t t lt r l rit r r ri l , s s t t t r s r ti it rr tl rri t t ri r ti r ss s s t t l t i l l si r s lts. , t r is si l i r t l i t r ti ll t : t r r i li s r ti s ( I ( ); i ( ); ( ); ( )) i t st lis i t si rit ri r i i i i ti s

* Corresponding author. Tel.: +39 055 2758739 ; fax: +39 055 2758755. E-mail address: margherita.vicario@unifi.it * orresponding author. el.: 39 055 2758739 ; fax: 39 055 2758755. - ail address: argherita.vicario unifi.it

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2452-3216

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti is is a e access article er t e - - lice se ( tt ://creati ec s. r /lice ses/ - c- / . /) eer-re ie er res si ilit f arc a a elli a tefa ia iti

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti 10.1016/j.prostr.2020.11.135

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on the recommended threshold levels for the ma in environmental parameters for conservation. Moreover the complexity of the involved factors and actors in the museum system, the need to arrange the people reception, who ask for different levels of cultural offer and services, the development of studies and research, having to cope with different legisla tions adopted in different Countries, thecosts reduction, energy consumption reduction and energy use ra tionalization, areneeds that require strong skills and specializations but, above all, interdisciplinarity, transversality, coordinationandcooperation betweendifferent professionals and experts. In particular, as regards the decay prevention of museum collections connected to microclimate, there are fundamental references as Thomson (1986) and Camuffo (1998), but only in recent years monitoring campaigns, carried out a imed at microclimatic, thermo-hygrometric and luminous control, as well as a ir qua lity control, became increasingly common (Corgnati et a l. (2009); D’Agostino et al. (2015) ; Ferdyn-Grygierek (2016)). Experimental measurement campaigns are rea lly a complex task, when the museum is housed in an historical building tha t usually requires conservation parameter va lues very different from those of works of art therein contained. The difficulty of defining an experimental set -up and a methodological approach connected to a specific measurement protocol is even more complex when the historical building has changed its functions and uses over time. Furthermore, the indoor microclimate study would be an essential tool for preventive conservation strategies, susta inable management of both artworks and historical building, and definition of reversible, sustainable, efficient and effective, minimally invasive and adaptive plant system solutions. The plant system placement in historical buildings is a lways a delicateandcomplex issue, because the environments havegenerally been thought anddesigned without any plant system, oftenbasedon natural ventila tionandpassivecooling stra tegies (Camuffoet a l. (2004); La Gennusa et a l. (2005); Sciurpi et a l. (2015); Litti and Audenaert (2018)). The ma in a im of our present research concerns the study of the microclimate of museum environment, for guaranteeing CH preventive conservation, based on the systemic analysis of the interrela tion effects due to thermodynamics of building system and operationandcontrol conditions of the plant system. The proposed methodological a pproachwas based on crucial levels of investiga tion: litera ture search and archive research aimed a t retrace the history of the building both in geometrical and materia l characteristics and change in use; geometrical and material survey and thermo-physical characterization; information and technical data on plant system (i.e. HVAC, lighting) and building management and usage profile; identification of timing and different periods of theyear formicroclimatic monitoringperforming; experimental data recordingandpost processing; results analysis and comparisons. The environment monitoring was based on stratigraphic and a ltimetric continuous measurements of the a ir temperature (T) and relative humidity (RH). The a ir velocityand meandifferential pressure varia tions in specific zones (i.e. grids placed on the base of thewa lls separat ing the cells and the access doors to these la tter) were a lso evaluated by spot measurements using a hot wire anemometer. Da ta were acquired every minute, using T and RH sensors and processed every 15 minutes. Some spot measurement performed by an infra -red FLIR thermo-camera (FLIR T600)with a da ta matrix of 480 ×360 pixels, an accuracy of ±2% or ±2 °C reading; thermal sensitivity 0.04 °C a t 30 °C; temperature range−40 °C to 650 °C, provided information on thesurface temperatureof the various buildingmateria ls, objects andcomponents. 2.2. Setting The monumental sectionof the Dominican convent, currently SanMarco Museum, in Florence, is the case study. The origina l structure of the convent dates back to the 13th Century and it was built by the Sylvestrian monks, while the present shape of the monumental complex dates back to the 15th Century when Cosimo de' Medici financed building renovation and extension, which was planned and executedby the architect Michelozzo. Between1437and 1442 the works were completed and in 1443 the convent was officially consecrated. After centuries, due to the 2. Methods andmaterials 2.1. Experimental set-up

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suppressionof religious orders, in the 19thCentury theconvent was expropriate and in 1869after some renovations, the monumental part of the complex was opened to public as the RoyalMuseumof SanMarco.

Fig. 1. (a) Photo: an external view of the San Marco Museum with the dormitory highlighted ; (b) Museum plan with the dormitory highlighted; (c) Photo: a view of the dormitory; (d) Photo: a view of the cell; (e) Photo: a view of the plant above the cells; (f) Photo: a view of the fan coil in the corridor Our experimental investiga tions were carried out in the area located on thefirst floor that surrounds the Cloister of San’Antoninoand which was the dormitories of the friars. The roomstill reta ins its origina l shape, is structured into three corridors onwhich are placed43 cells andholds oneof the most important cycles of renaissance frescoes byFra Angelico between 1438 and 1445 (Fig. 1a -1d). The historical buildingconversion into a Museum, which tookplace in 1869, hadgiven rise to several interventions for functional adaptation of the rooms. The roomwas never equipped with hea ting ventilation a ir conditioning (HVAC) system until the ‘90s when some fan coils were loca ted in the corridors. Since 2013 theDormitorywasequippedby a variable refrigerant volume system (VRF). At the extrados of the vault at 3 m from thefloor, eighteen indoor units are locatedand areequipped by a temperature control unit through a centralized system, but without humiditycontrol (Fig. 1e-1f). 3. Microclimatic monitoring The experimentalmonitoringcampaign was performed from31 July 2019 and is still in progress. The a im of the experimental investigation was the comprehension of the influence of external and internalmicroclimatic effects on the interna l thermo-hygrometric conditions to guarantee the suggested va lues by UNI 10829 (1999) and MiBAC (2001) for CH preventive conservation. The cross-checkingof information obtained with preliminary investigations, (i.e. bibliographic andarchival study, surveyandanalysis of the existing status) allowed the identificationof themost significant zones reducing costs and time of the experimental setup. The cell 26 and its surrounding ambient were chosen because of its central loca tion and for its proximity to the Madonna delle Ombre by Fra Angelico, one of the three wa ll pa intings located in the corridors. The second corridor is 45,5 m length, 2,50 m wide, the pitched roof is 6,97 m high a t the ridge; the cells placed onboth sides of the corridor are 3,70 m length, 2,75 m wide and the barrel vault is 3,35 m a t the apex (Fig. 2). Technical data of the used instruments are provided in Table 1. They were located in compliance with the least visibility and invasiveness. The sensor location is provided in Fig. 2. PT01 inside the cell 26 a t 2,80 m from the ground; PT02 inside the cell 25 a t 3,00m from the ground; PT03 on the ledge in the corridor near thewa ll pa intingat

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3,65 m from the ground; PT04 on the ledge on the other side of the corridor a t 3,65 m from theground; PT05 in the corridor a t floor level. The correspondingexternalmicroclimatic data provided by “ Consorzio LAMMA. Laboratory for Meteorology and Environmental Modelling ” (located 6,4 km far from San Marco Museum) were analysed and used.

Fig. 2. (a) Dormitory plan and localization of sensors (b) Photo: localization of sensors in the corridor

Table 1. Main characteristics of the sensors.

Tinytag Plus 2 TGP-4500

Extech RHT10

Dimensions

34x51x80 mm - 25 to + 85 °C

Dimensions

130 x 30 x 25mm - 40 °C to +70 °C ± 1 °C (-10 to 40°C)

Temperature Range Temperature Accuracy Temperature Resolution

Temperature Range Temperature Accuracy Temperature Resolution

±0.5 °C (0 to 40°C)

0.01 °C

0.1 °C

RH Range

0 % to 100%

RH Range

0 % to 100%

RHAccuracy RH Resolution

± 3 % 0.3 %

RHAccuracy RH Resolution

± 3 % 0.1 %

4. Results anddiscussion In this present section, experimental da ta analysis and post processing for the period from 31 July 2019 to 28 October 2019 are presented and discussed. In this period the centralized cooling system was on from 31 July to 17 Octoberwith a temperature set point of 23°C, without anyhumiditycontrol. From 18 t o 28October the plant was off. The sta tistical data analysis anddata error evaluation for thewhole periodare provided in Table 2. The mean standard devia tion for T and RH is respectively 0,93and 2,84. The mean chi-squared error is 1,45% for T and 2,55%for RH. The results showed the reliability andvalidityof the measurement method and obtained results.

Table 2. Statistical data analysis and error evaluation.

Mean T (°C)

Median T (°C)

Maximum

Minimum

Standard Deviation

Chi-squared %

RH (%)

RH (%)

T (°C)

RH (%)

T (°C)

RH (%)

T (°C)

RH (%)

T (°C)

RH (%)

PT01 PT02 PT03 PT04 PT05

24,2 23,1 23,1 23,4 22,9

55,1 57,1 57,2 57,6 58,1

24,2 23,1 23,2 23,6 23,0

55,3 57,2 57,5 57,6 58,2

28,1 25,6 25,1 25,2 24,2

64,9 63,4 63,9 64,8 65,3

21,2 20,9 21,1 21,5 21,0

40,0 47,1 48,3 49,0 45,3

1,57 0,88 0,71 0,79 0,70

4,01 2,60 2,41 2,47 2,72

1,90 1,43 1,28 1,36 1,28

3,05 2,45 2,36 2,39 2,51

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T and RHtrends for eachmeasurement point during the entire monitoredperiod are shown in Fig. 3. It canbenoted the stability of the indoormicroclimate parameters: the maximumdaily range of T is 3,4°C andof RHis 16% in PT01 inside the cell, and 1,6°C and 10,3% in PT03 in the corridor. T and RH range values during the entire monitoring campaign, calculated both for the period with plant on (from 31 July 2019 to 17 October 2019) and with plant off (from 18 October to 28 October 2019), are a lways low due to thermo-physical behavior of the building (i.e. high thermal inertia and capacity). In particular, the mean daily T range in the period with the plant on is lower than that one of the period with plant off, while the da ily RH range in the period with t he systemon is grea ter than that one of the period with the plant off. This is due to temperaturecontrol system that does not provide thecontemporary relative humidity regula tion. The experimental da ta were analysed and discussed referring to the UNI 10829 (1999) and MiBAC (2001) recommendations. The cycle of painting inside the cell and the Annunciazione in the first corridor were pa intedwith the frescos technique, while the Madonna delle Ombre in the secondcorridorwas paintedby“dry”, a rare techni que in the Fra Angelico’ art. Restoration works and investigations carried out before the installation of the HVAC system show that the decorative and structural elements of great value did not have serious decay and instability phenomenadue to the indoor environment. Thefamous restorerDino Dini, who restored the wall pa intings between 1975and1983 reportedas primarycauses of the decayphenomena on the frescoes thepassage of time, dirt, scra tches, abrasions, blackening of candle fumes, damage due to the many repainting that were cause of the bad readability of the frescoes and of the proliferationof mould.

Fig. 3. (a) Air Temperature trend and (b) Relative Humidity trend for the entire period

The EN1575 (2010) standard introducesthe concept of “historical climate” and defines as suitable for conservation those va lues rela ted to the environmental history of the object. Unless there are no degradation phenomena, the standard suggests not toa lter this climatic condition. Inour case due to the introduction of theHVAC systemwas not possible to trace themicroclimatic conditions in which the artworks acclimatizedand preserved for centuries before, so we referred to the ranges of T andRH as suggested in UNI 10829 (1999) and to MiBAC (2001). These limits are given in Table 3. Table 3. Limits suggested by the current standards for wall paintings conservation. UR (%) D (UR)max (%) T (°C) D (T)max (°C) UNI 10829: 1999 55-65 - 10-24 MiBAC 2001 45-60 - 6 -25 ± 1,5/h

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Experimental da ta were ana lyzed according to UNI 10829 (1999). This standard provides for each climatic parameters thecalculationmethod of the deviation index, defined as the percentage of time in which theparameter is found to beoutside therange of values suggested for the conservation of a categoryof artwork. Cumulative frequency was plotted to ca lculate the Performance Index (PI) as an indica tor of the conservation quality of the indoor environment in rela tion to the type of goods preserved. PI represents the percentage of time in which the parameter rema ins within the range suggested. The calculation of cumulative frequency and PI of T and RH given in Table 4, a llowed the assessment of the suitability of the va lues for the preservation of wa ll pa in tings. Fig. 4 shows the comparison of the limits suggested by UNI 10829 (1999) and MiBAC (2001) and the T and RH values distribution during the entire monitoringcampaign. Even if the individual values of PI are good, Fig. 4 shows howthe values are not contemporarily verified for T and RH. In particular, the PI for the measuring point PT01 inside the cell is very low due to the significant influence of the lighting system whoaffects the indoor environment conditions.

Table 4. Performance Index (PI) values for T and RH.

Performance Index (PI)

Position of the sensors

UNI 10829: 1999

MiBAC 2001

UNI 10829: 1999 e MiBACT 2001

T (°C) 43,89% 86,78% 93,06% 78,43% 99,79%

RH (%) 55,79% 78,63% 82,15% 83,29% 87,80%

T (°C) 69,28% 99,61% 99,95% 99,35% 100,00%

RH (%) 88,87% 85,95% 87,82% 83,24% 72,78%

T (°C) 43,89% 86,78% 93,06% 78,43% 99,79%

RH (%) 55,32% 72,94% 78,47% 75,58% 66,06%

PT01 PT02 PT03 PT04 PT05

After checking T and RH va lues stability for the artworks conservation, potential variations in the interaction between buildingandenvironment were assessed. The impact of the outdoor and indoor environmental variables (e.g. HVAC plant, lighting system, visitor and staff) were analyzed and discussed. Comparison of outdoor and indoor T trend in the period with plant off, from18 to28of October, shows howthe thermal inertia andcapacityof thebuilding significantly reduce fluctuations. E.g., Fig. 5 shows the outdoor and indoor T trend in PT04, the meanvalue of T is 22,2 °C, the maximum is 23,3 °C and minimum is 21,5 °C with a meandaily rangeof 0,8 °C. In particular, the phase shift of thermalwave is evident: e.g. a t 6:00 of the 18 ofOctober the external T is 11,4 °C and the internal T is 21,8

Fig. 4. Distribution of T and RH for the entire monitored period compared with the limits suggested by UNI 10829 (1999) e MIBAC (2001) in (a) PT01 e PT02 in the cells and (b) PT03, PT04 and PT05 in the corridor.

°C and at 21:00 the externalT is 17,1 °C and the internalT is 22,3 °C. This is due to the thermophysical behavior of

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massive building. It can be noted that the plant working conditions produce a damping effect on the outdoor environmental load, combinedwith the appreciable thermal properties of thebuilding. Results showthe plant system efficacy for guaranteeingpreventive conservationconditions but also it important adaptivity and acclimatizationdue to its thermal peaks dampingeffect, and microclimatic extreme variations reduction, tha t are the most damaging for artworks and building. Building thermo-physics combined with plant working conditions, assure stability requirements of microclimate that play a key role in the deterioration processes. Varia tions in thermo -physical parameters that ate as damaging as their absolute values, are reduced. The humidity ratio (x; i.e. the ra tio between mass of wa ter vapour and dry air, g r /kg)was ca lcula tedusing the sa turation pressure evaluatedas function of T and RH.

Fig. 5. Air Temperature trend for the period with plant off (from 18 October to 28 October 2019)

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Fig. 6. Mean hourly value of T, RH an x during closing and opening hours of the museum for the entire period in (a) PT01 and (b) PT04

The influenceof indoor thermal loadswas identified bycalculation ofmeanhourly valueof the thermo-hygrometric parameters referring to three user profiles: closingdays, openingdays from8:00 to14:00 and openingdaysfrom8:00 to 17:00. E.g., graphs for T, RH andx in PT01andPT03 are shown in Fig. 6. It canbe observed that during the closing days, thevalues of T, RH andx remain stable with minimal variations, while during the closingdays there is a rise in T and a decrease in RH during the openinghours. The switchingon the ligh ting system is the main cause of theT rise in PT01. This rise is a lso in PT03 a lthough lower. Ana lyzing the x value variations during the entire monitored period for both indoor and outdoor environment, it can be noted that theamount of internal vapor andconsequently the la tent heat loads are not very appreciable because are only due to the lowvisitors presence. Therefore the efficacy of VRF system for the control of the microclimatic conditions stability is guaranteed. As a matter of fact, the VRF solution is the best formuseums and exhibitions inside massive historic buildings, characterized by large volumes, without appreciable and impulsive latent loads. Only in the farther zones from the HVAC units and luminaires (i.e. PT04, PT05) and where the highest concentration of visitors was checked. It canbenoteda rise in T andRH with a x value increase. Fromdata analysis it canbe observed a non-homogeneous distributionof temperaturevalues with a vertical gradient of about 1°C between thePT05 located on the floor, and thePT04 located on the ledge, andwith a horizontal gradient of about 1°Cbetweenpoints PT03 and PT04 both located on the ledge, PT03 located closer to the indoor a ir units.

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5. Conclusions Results showed that the proposed experimental approach can be a useful tool for a methodological study of CH sustainable adaptive reuse with a viewto conservationand preventive protection, based on a deepknowledge of the buildingphysics and its indoor environment connected to plant system thermodynamicsandcontrol/regulation system presence. It canbe extended, by means of specific adjustment, to a ll similar cases, but a lso non -listed buildings and current designs. The proposedmethod is a lso an operative andpractical tool for assessing the sustainability, feasibility and effectiveness of non-invasive, reversible systemsolutions based on theconcept of plants acclimatization . It allows sustainable , a daptive and acclimatization concepts quantificationaimedat identifying thedegradation risk. It provides a lso the fundamental approach for the analysis of the plant systemworkingby a viewof its slowly andprogressively adaptation to thermo-physical building behaviour. Only in the long term, it should lead to the internal microclimate and a ir quality for the optimal conditions of artwork andbuildingconservationandpeople healthandwell-being. The practical applica tion of the method can provide a useful support in decision making about the choice of the most compatible and sustainable environmental control strategies such as passive control, ventilation solutions, movable and reversible local plant equipment. Acknowledgements The authors thank: Dr. Stefano Casciu, Director of the Polo Museale della Toscana ; Dr. Marilena Tamassia, Director of the Museo di San Marco ; Ms. Stefania and the staff of the Museum; Dr. Luca Fibbi of the Consorzio LAMMA ; the TechnicalDirector and the staff of TecnoengineeringS.r.l.; Luigi Puglioli of the Agenzia Benvenuti . References ASHRAE 2011. HVAC Applications. ASHRAE Handbook, ISBN 9781936504077. Camuffo D., 1998. Microclimate for cultural heritage. Elsevier, Amsterdam, ISBN: 9780444829252. Camuffo D., Pagan E., Bernardi A., Becherini F., 2004. The impact of heating, lighting and people in re-using historical buildings: a case study, Journal of Cultural Heritage 5, 409 – 416, doi:10.1016/j.culher.2004.01.005. Corgnati S., Fabi V., Filippi M., 2009. Amethodology for microclimatic quality evaluation in museums: application to a temporary exhibit, Building and Environment 44, 1253-1260, doi:10.1016/j.buildenv.2008.09.012. D’Agostino V., D’ambrosio Alfano F.R., Palella B., Riccio G., 2015, The Museum Environment: A Protocol for Evaluation of Micr oclimatic Conditions, Energy and Buildings 95 pp. 124-129, doi: 10.1016/j.enbuild.2014.11.009. EN 15757 2010. Conservation of Cultural Property - Specifications for temperature and relative humidity to limit climate-induced mechanical damage in organic hygroscopic materials. Ferdyn-Grygierek J. 2016. Monitoring of indoor air parameters in large museum exhibition halls with and without air-conditioning systems. Building and Environment 107, 113-126, doi: 10.1016/j.buildenv.2016.07.024. La Gennusa M., Rizzo G., Scaccianoce G., Nicoletti F., 2005. Control of indoor environments in heritage buildings: experimental measurement s in an old Italian museum and proposal of a methodology. Journal of Cultural Heritage 6, 147 – 55, doi:10.1016/j.culher.2005.03.001. Litti G., Audenaert A., 2018. An integrated approach for indoor microclimate diagnosis of heritage and museum buildings: The main exhibition hall of Vleeshuismuseum in Antwerp. Energy and Buildings 162, 91 – 108, doi: 10.1016/j.enbuild.2017.12.014. MiBAC D.M. 10 maggio 2001 (2001). Atto di indirizzo sui criteri tecnico-scientifici e sugli standard di funzionamento e sviluppo dei musei, Italian Standard. Sciurpi F., Carletti C., Cellai G., Pierangioli L., 2015. Environmental monitoring and microclimatic c ontrol strategies in ‘La Specola’ museum of Florence. Energy and Buildings 95, 190-201, doi: 10.1016/j.enbuild.2014.10.061. Thomson G,. 1986. The Museum Environment. Butterworths, London, ISBN: 9780750612661. UNI 10829 1999. Works of art of historical importance. Ambient conditions for the conservation. Measurement and analysis,. Italian Standard.

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Procedia Structural Integrity 29 (2020) 157–164

Art Collections 2020, Safety Issue (ARCO 2020, SAFETY) Code-compliant structural design for site specific works of art: a case-study Leonardo Zaffi a *, Antonio Capestro a , Stefania Viti a a Dipartimento di Architettura (DIDA), Università di Firenze, via della Mattonaia 14, 50121 Firenze Abstract The multi-cultural metropolis presents a large number of spontaneous art endeavours. The street-art and site specific contemporary art earned a special role in the urban renewal; they can be considered as a potential source of urban regeneration, becoming a possible catalyst of the needs of the community, involving the inhabitants in a new vision of urban space and inducing a crea tive change of the cities (Zaffi 2017). These interventions, sometimes, are difficult to classify under a structural point of view: indeed, they are temporary art works, whose dimensions and properties confer them a structural role in the urban scenario. In this paper an experience made in Florence is presented, erasing from the cooperation between the University of Florence and the artist Clet. The intervention consists of creating a big temporary three-dimensional nose-shaped staging which should change the façade of a forsaken industrial building, currently located in a modern residential area. The purpose of the staging was to enhance the area, underlining the role plaid by the building, which is the symbol of the industrial identity of the town in the first half of the XX century. The experience, part of a research funded by a local real estate company, involved the students of the School of Architecture of Florence in a whole project experience from the design phase to the building site where they, practising themselves i n self build techniques, and together with the artist, realized the work of art. A multidisciplinary team, coordinated by the authors, lead the activities from the image promotion to the final construction of a big wooden structure of over than 12-meters length. A big nose called “Maso” would have to turn the façade of the old power plant in a friendly face. The placement of the artwork on the façade has been a crucial step. Indeed, at the time, there were no specific requirement to comply for the structura l safety of the artwork. Nevertheless, the dimension and the location of the object leaded to face the structural issue; the building company, which had the technical responsibility of the staging, decided to hang the wood structure through a couple of heavy hooking plates to fix at the façade walls. The plates, however, increased very much the global weight of the artwork, and – consequently - the structural complexity of the staging. Therefore, a special structural investigation was made, without following the usual procedures, to check the safety of the staging. In these last months, the Regional Government of Tuscany introduced a technical requirement for temporary constructions and art works, which, anyway, only partially helps the safety assessment of the case-study.

* Corresponding author. Tel.: +39 055-2755447 E-mail address: Leonardo.zaffi@unifi.it

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti 10.1016/j.prostr.2020.11.152

Leonardo Zaffi et al. / Procedia Structural Integrity 29 (2020) 157–164 Zaffi, Capestro and Viti / Structural Integrity Procedia 00 (2019) 000 – 000

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© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti Keywords: Artifacts; safety of artifacts; blast hazard; vulnerability of case-studies; FE analysis. 1. Introduction The paper describes an experience made within the School of Architecture of the University of Florence together with Clet (Abraham2016, https://it.wikipedia .org/wiki/Clet_Abraham), a well-known representative of the street art, and a loca l rea l estate company. The experience consisted in the creation of a big temporary three-dimensiona l nose shaped staging which should change the façade of the Power Station, a forsaken industria l building, currently loca ted in Novoli, a modern residential area of Florence. Clet has a lready made severa l urban site-specific interventions in the town (see Figure 1), having different dimensions and duration. One of these interventions (Figure 1a) consisted of a wood-made nose-shaped sculpture which was located on the vertica l wa ll of the San Niccolò tower, in Florence. The sculpture was very light, and it was fixed a t the wall through some chords, without followingany specific technical requirement. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of Marco Tanganelli and Stefania Viti

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Fig. 1. Some urban interventions made by Clet: a. temporary art installations at the San Niccolò tower (Florence), b and c. “Eyes” of Prato Project” a temporary staging of the gates in the walls of the ancient city of Prato, d. Examples of art bombing on road signs: maybe the most famous Clet’s art works. (photo credits a,b,c by Clet) The current intervention had the purpose to enhance the area, underlining the role pla id by the Power Station, which is the symbol of the industria l identity of the town in the first ha lf of the XX century. The experience consisted of both the design and the rea lization of the intervention, and it involved a multidisciplina ry team, coordinated by the authors. The sculptu re consisted in a big nose ca lled “Maso”, having a light wood truss structure; it had to stand on the building façade for some months, before the beginning of a renewa l intervention on the building. Despite its temporary dura tion, the intervention had to face the possible cha llenge of the weather (ra in, wind etc.), since the

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assembly was planned for December (wintertime in Ita ly). The possible loading conditions related to the weather have required to put a specia l attention to the stability of the intervention; furthermore, the intervention was planned together with the municipa l administra tion . In this case, therefore, it was not an “underground” and spontaneous initia tive, but it had to be doneaccordingwith the existing roles for temporary structures. The need to comply specific technica l requirements evidenced a serious lack of roles for these cases; in fact, there were not ava ilable instructions for procedures compatible to the case-study. The requirements provided by the Tuscan Government, i ndeed, were not suitable to be adopted. As a result, a further “actor” was involved in the process, i.e. an engineer specifica lly skilled in temporary insta llations. Despite his intervention, however, there has not been a positivesolution of the problem, and the intervention has never beencompleted. This experience has evidenced a lack of opera tive roles to perform non-conventiona l interventions in the respect of the lega lity; in the following this experience has been described, and the inconsistencies of the technica l legisla tion in this ma tter have been evidenced. 2. Planning anddesign 2.1. The old industrial center in Novoli Novoli is a district of Florence which developed in the middle of the XX Century (Biagi 2008). At the end of the 30s, an important industria l building was made in this area for the FIAT company, according to the project made by the architect Vittorio Bonadé Bottino (Signorelli 1988). Few years after the beginning of its construction, the company moved its headquarters from Florence to Turin, which became its officia l location. The industria l complex, anyway, was constructed (see Figure 2a) , thanks to a specia l agreement with the “ Società Anonima ” of Florence. With the urban development occurred after the WWII , the industria l complex represented a barrier for the expansion of the town. The most part of the buildings constituting the industria l complex have been demolished in the last decades of XX century, whilst the power station (shown in Figure 2 b,c) has been left as a symbol of the former arrangement of the quarter. In these last years, the quarter has been largely developed, becoming the most modern pole of the town. The building is surrounded by modern devices, such as the metro -line, inaugurated in December 2018, a shopping center and an urbanpark.

a c Fig. 2. a. The old industrial complex in Novoli. b,c. External and internal views of the Power Station. b

2.2. The Power Station The Power Sta tion is a tower-building; it has a squared plan with the sides of about 20m, and a globa l height equa l to 31 m, besides a chimney 50-meters ta ll. It has two interna l floors only, respectively at the levels of 5m and 22m. There is another open floor, a perimeter ga llery, a t the height of 27m, 4 meters belowtheplane roof.

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The design of the Power Station goes back to 1938-1940, and its construction has been made between 1939 and 1945. It has a RC structure, made of column and beams, whose design has been made according to the technica l regula tions of the time (R.D.1981-4/09/1927; R.D.2229-16/11/1939), which, of course, differ very much form the current standards and do not include any specification regarding the seismic hazard. The curta in wa lls consist of two different layers of masonry wa lls, respectively made of an externa l layer of masonry bricks and an interna l a ir bricks one. In 2019, within a restoration program, a careful survey has been made on the structure, in order to check its structura l capacity and degradation level. A Knowledge Level equa l to 2 (NTC 2018) has been achieved, after the performing of an extensive number of in-situ tests, including 26 core crushing ana lysis on both beams and columns (the structura l investigation was made by Ing. M. Micheloni), and a dynamic identification ana lysis has been made, in order to set the structura l model. The assessment of the safety level of the structure is still in progress; the building, however, will be recovered and addressed to catering and public functions, respectively. In this scenario, the “Maso”projectwas aimeda t collecting thea ttentionof thepopulation on the bu ildingand the rela tedprojects. 2.3. The project: teamorganizationandmaincontents The experience has been promoted by Clet; he was required to develop the project by “Immobiliare Novoli” , a private Rea l Estate company which wanted to promote urban interventions to improve the interest of the area . Despite he used to work by himself, in this occasion Clet decided to involve the Department of Architecture of the University of Florence, to change his approach to design, and share this experience with the students. After the agreement between Clet, Prof. Zaffi and Prof. Capestro, a specia l class has been started a imed at working at this project. The students have been involved in the experience starting for the very first step, i.e. the choice of the shape and the dimensions togive to the sculpture, the material to use for its construction, and the structuralmodel to adopt. The meeting of the class with professors and Clet, as well as the design and the construction of the nose -shaped sculpture, took place in a specia l University-room dedica ted to carpentry and hand-made activities, equipped with tools and power tools for shaping and wood working, whose dimensions played a role in the construction organization.

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Fig. 3. Sketch (a) and models (b,c) of the project.

The proposed intervention , named “Maso” (a Tuscan traditiona l name chosen to give a sense of friendliness to this art work), consisted in the creation of a three- dimensiona l “nose” to stand on the façade of the Power Station, in

Leonardo Zaffi et al. / Procedia Structural Integrity 29 (2020) 157–164 Zaffi, Capestro and Viti / Structural Integrity Procedia 00 (2019) 000 – 000 5 order to give to the façade the appearance of a human face. The project, planned by Clet, has been initia lly defined through sketches (Figure 3a) and models (Figure 3b, c). When the sculpture has been defined in its shape and dimensions, the constructive phase has been planned. A wood frame has been chosen for the structure, due to its light weight and to the constructive simplicity, compatible with the skills and the operative background of the students. The external skin, instead, was planned to be made by wood sheets. 3. The “Maso” p roduction The construction of the sculpture has been made by Clet, together with the students, inside the specia l University room dedicated to carpentry works (Capestro and Zaffi 2018). The room is placed at the ground floor of the University complex, it is very large for Ita lian standards, and it has a large externa l door, suitable for moving the sculpture from the room to the outside courtyard. Nevertheless, the length of the room was shorter (about 1/3) of the tota l length of the sculpture; moreover, the sculpture had to be moved from the University to the Power Station through a simple van. As a consequence, the sculpture had to be made in three pieces each time, and each of them had to be completely disassembled just after its first construction. In this section the construction phases have been described. 3.1. The construction in the University room The carpentry room (Figure 4a) has a plan of 6.15 x17.10 x m, and a height equa l to 4.50 m. The sculpture consisted of a frame of paulownia wood, fixed by glue and na ils. The dimension of the sculpture was 12,50x4.00x3,70m; therefore, it had to be divided in five parts (three for the ma in septum and two for the “nostrils” of the nose), eachof whichhad to bemade separately. 161

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Fig. 4. The construction phase inside the carpentry room ( Laboratorio di Architettura e Autocostruzione ): (a, b) Laboratory technicians, students and Clet at work. (c) Testing the preassembly of the structure

The entire project had to be performed within the time of a semester (between September and January). Moreover, the “Maso” inaugura tion was planned for December 15 th , during the pre-Christmas activities, just after the opening of the newmetro-line of the area. As a consequence, the construction phase had to be very limited in the time; indeed, it started at November 9 th and ended on November 26 th . In order to be able to complete the construction activities in this short time, the students had to work well beyond their officia l lesson time; a proper organiza tion was made, to have different teams, made by 5-6 students each, which covered the entire opening-time of the University. A superposition of two students was made between the previous team and the following one, in order to assure continuity to the construction. In Figure 4b and 4c some images of the construction phase can be seen.

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3.2. Transfer to thePower Station e final re-assembly The transfer to the Power Station was made through a van (Figure 5a), which required the complete disassemble of the three parts of the sculpture. All the batons have been numbered, in order to help the successive re-assembled of the truss system. The re-assemble of the sculpture had to be made in the yard next to the Power Station, both for safety reasons, and for the impossibility to go through the doors with the sculptures. Therefore, a cover has been made next to the building, in order to hold the re-assembling activities (Figure 5 b,c). The fina l re-assembly was made by gluing a ll the batons according to the initia l position. After the “structure” re -assembling, the wood sheets have been put (see Figure 6), to create the externa l skin of the sculpture. The wood sheets have been fixed to the structure through na ils and finished with waterproof pa ints. The fina l step of the work should be the fixing of the sculpture to the building façade. This step, however, was never achieved, as explained in the Section4.

a c Fig. 5. a. The van used for the sculpture moving; b.working site next to the Power Station; c. Re-assembling the Maso on site. b

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b c Fig. 6. a. Completing the structural frame. b. The covering of the structure with wood sheets. c. Finally the “Maso” is finished and ready to be hung on the façade of the power station. 4. The safety matters and the (lack of)Code requirements 4.1 Structural modelingandCode requirements From the very beginning, it was clear that the choice of how to fix the “nose” to the façade would be taught. The ma in choice was between a light and a firm connection. Indeed, a very light connection, for instance made of

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chords, would have the advantage not to overload the system; in this case, however, it would be difficult to assure to the sculpture the due stability in case of strong wind. At the opposite, a strong fixing disposa l should give a higher stability to the system, but it would substantia lly change its globa l mass, requiring much more attention to the connection with the building. Moreover, it would be very different in stiffness and mass by the wood truss “nose”, presentingpossible interaction problem. Another substantia l issue was about who had to be in charge of the lega l responsibility of the system safety. Indeed, even if the entire process was developed within the University, the Rea l Esta te Company was responsible for its management. The power station, in fact, was owned by the Rea l Estate Company until it is fina lly refurbished and transferred to the Municipalityas a part for theurbanization fees of the area. Despite the hazard rela ted to the suspended sculpture was negligible, the Rea l Estate Company could not avoid to face the technica l legislation. The proper procedure to represent the structura l behavior of the sculpture was not easy to understand. Florence, like a lmost any other town in Ita ly, is subjected to a moderate seismic hazard, and a ll the architectura l interventions must be checked in order to assess their structura l and seismic safety. In this case, however, there was not a structura l project, and even the geometry of the truss system was created time-by-time, without a precise scheme. Moreover, the acceptance criteria provided by the Technica l Code refer to more conventiona l structures, and they cannot by simply extended for systems so much different to them. Therefore, the structura l problems to face would be: i) gettinga structura l scheme of the system, ii) representing the strength of the connections, iii) finding referenceresponsequantities to compare to thestructural behavior of thesystem. The representation of the structura l scheme requires a laser-scanner survey, to be done getting into the sculpture. The process followed for the construction, in fact, was only partia lly planned, and severa l changes have been made on the basis of observations rela ted to thequality of the obtained results. The modeling of the joints (see Figure 7) was a problem not easy to overcome. They have been done by not qua lified operators, without a standard qua lity-controlled process. Moreover, each connection has been de-assembly and re-assembly, as a consequence of the transportation need. The qua lity of each connection, therefore, could be different from the others, for the occurring of imperfections or the degrade of the wood subjected to the repeated works.

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Fig. 7. Connections of the wood-truss system and the steel plates for the connection to the building.

Fina lly, the verification of the safety of the structure would be easy to pursue only in terms of elastic stress; the amount of latera l displacement, indeed, would need of reference parameters which a re provided by the current Code

only for very different structures. 4.2 (Lack of) technical provisions

The need to face the Technica l Codes prevented the respect of the initia l schedules. The Company had to take some time to face these problems, and it decided to ca ll an engineer with a specific experience in checking the structura l behavior of temporary and unconventiona l structures. The procedures and the assumptions to adopt in case of new buildings and structures (NTC 2018, Circolare Ministeriale 2019) are very efficient and easy to understand.