buildings Article Mechanical and Typological Characterization of Traditional Stone Masonry Walls in Old Urban Centres: A Case Study in Viseu, Portugal José Carlos Domingues 1, Tiago Miguel Ferreira 2,* , Romeu Vicente 3 and João Negrão 4 1 Department of Civil Engineering, University of Coimbra, 3030-788 Coimbra, Portugal; [email protected] 2 ISISE, Institute of Science and Innovation for Bio-Sustainability (IB-S), Department of Civil Engineering, University of Minho, 4800-058 Guimarães, Portugal 3 RISCO, Department of Civil Engineering, University of Aveiro, 3810-193 Aveiro, Portugal; [email protected] 4 Department of Civil Engineering, University of Coimbra, 3030-788 Coimbra, Portugal; [email protected] * Correspondence: [email protected]; Tel.: +351-253-510-200 Received: 19 December 2018; Accepted: 4 January 2019; Published: 9 January 2019 Abstract: Essential for any intervention in existing buildings, a thorough knowledge of both structural and material characteristics is even more important in the case of traditional stone masonry buildings, due both to the variability of this technology’s properties and the degradation buildings might have sustained. In Portugal, a number of in situ and laboratory experimental campaigns has allowed us in recent years to expand the knowledge on the mechanical properties of stone masonry walls. Nevertheless, the existence of different wall typologies built with the same material necessitates that this characterization takes into account the various regional constructive cultures. This paper presents the results obtained through an in-situ characterization campaign carried out in the old urban center of Viseu, for which there is no information available in the literature. Granite stone masonry walls of two different buildings were analyzed and characterized considering their geometrical and material features, contributing to the identification of stone masonry typologies present in the city’s old urban center. Flat-jack testing yielded resistance and deformability parameters to be used both in safety evaluation and intervention design. The properties obtained can be said to be consistent with those deriving from other experimental campaigns, conducted in granite walls of different typologies, throughout the country. Simultaneously, relevant conclusions about the use of flat-jacks to characterize this type of stone masonry were drawn. Keywords: masonry characterization; mechanical properties; in situ test campaign; granite masonry; flat-jack testing; old urban center; regional constructive cultures 1. Introduction When intervening in existing buildings, and with a view to preserving historical and material authenticity, no action should be conducted without being absolutely necessary. To ensure this, a deep knowledge of structural and material characteristics, constructive technologies and techniques, changes made over time, and current state of the building is fundamental [1]. This necessity is all the more pressing when dealing with stone masonry buildings, as their structural behavior is significantly different from recent buildings (generally consisting of reticulated reinforced concrete structures), besides also presenting high typological and mechanical variability, which are quite dependent of the local material availability and constructive tradition. The characterization of the mechanical behavior of granite stone masonry, a typology common in the North and Center-North of Portugal, has already been the subject of some studies conducted Buildings 2019, 9, 18; doi:10.3390/buildings9010018 www.mdpi.com/journal/buildings Buildings 2019, 9, x FOR PEER REVIEW 2 of 20 Buildings 2019, 9, 18 2 of 20 The characterization of the mechanical behavior of granite stone masonry, a typology common in the North and Center‐North of Portugal, has already been the subject of some studies conducted both in situ [[2,3]2,3] and inin laboratorylaboratory [[4–7].4–7]. Nevertheless, the existence of various regional constructive cultures, resulting resulting in in different different wall wall typologies typologies built built with with the the same same material, material, leads leads to the to need the need for such for suchcharacterization characterization to take to takeinto into account account the the specific specific locations locations where where these these walls walls are are representative. representative. Regarding the specificspecific case of thethe citycity ofof Viseu,Viseu, itit isis worthworth mentioningmentioning thatthat informationinformation concerningconcerning thethe mechanical properties of granite stone masonry walls in its old urban center is absent. Therefore, and aiming at providing data that can help to retain the original structural system of these buildings, whilewhile ensuringensuring structural structural safety, safety, this this work work intends intends to to offer offer a firsta first contribution contribution to to the the characterization characterization of theseof these elements. elements. It is It intended, is intended, namely, namely, and apartand apart from from geometrical geometrical and material and material characterization characterization which canwhich contribute can contribute to the identification to the identification of stone of masonry stone masonry typologies typologies frequent frequent in the old in urban the old center urban of Viseu,center toof quantify Viseu, to resistance quantify and resistance deformability and deformability parameters to parameters be used both to inbe safety used evaluationboth in safety and interventionevaluation and design. intervention Thus, this design. paper Thus, presents this paper and discusses presents theand results discusses obtained the results from obtained an in situ from test campaignan in situ test conducted campaign in theconducted old urban in the center old of urban Viseu. center Granite of Viseu. stone Granite masonry stone walls masonry of two different walls of buildingstwo different were buildings analyzed were and characterizedanalyzed and consideringcharacterized their considering geometrical their and geometrical material characteristics. and material Flat-jackcharacteristics. testing Flat technique‐jack testing was used technique to obtain was resistance used andto obtain deformability resistance parameters and deformability to be used bothparameters in safety to evaluationbe used both and in intervention safety evaluation design. and Relevant intervention conclusions design. about Relevant the useconclusions of flat-jacks about to characterizethe use of flat this‐jacks type to of characterize stone masonry this type were of also stone drawn. masonry were also drawn. 2. The City of Viseu: Brief Urbanistic and Constructive Characterization The city of Viseu Viseu plays plays an an important important role role in in the the history history of of Portugal, Portugal, as as it itis ismarkedly markedly linked linked to tothe the figure figure of Viriathus, of Viriathus, a tribal a tribal leader leader who who resisted resisted the Roman the Roman invasion. invasion. In fact, In since fact, Roman since Roman times, times,Viseu has Viseu assumed has assumed a prominence a prominence in the nearby in the settlements. nearby settlements. Following Following the ancient the Roman ancient urbanistic Roman urbanistictradition, the tradition, city developed the city developed around two around main two roads, main the roads, cardus the, orientedcardus, orientedNorth‐South, North-South, and the anddecumanus the decumanus, oriented, oriented East‐West. East-West. This influence This influence can still can be still seen be seentoday, today, as both as both roads roads evolved evolved to be to beprominent prominent axis axis of the of the city’s city’s old old urban urban center center (Figure (Figure 1).1 ). Figure 1. View of the old urban center of Viseu. ItIt was during the XVI century that Viseu started expanding outwards towards its ancient walls. ItIt was also byby thisthis timetime thatthat thethe areaarea nowadaysnowadays knownknown asas RossioRossio startedstarted gaininggaining importance;importance; by thethe XIXXIX century, itit wouldwould havehave becomebecome thethe newnew civiccivic center of the city, withwith thethe constructionconstruction ofof the town hall building.building. Nowadays, Nowadays, with with 73,518 73,518 inhabitants inhabitants in its in urban its urban perimeter perimeter [8], Viseu [8], isViseu the second is the biggestsecond Buildings 2019,, 9,, 18x FOR PEER REVIEW 3 of 20 biggest city in the Região Centro of Portugal, as well as the largest urban center outside both city in the Região Centro of Portugal, as well as the largest urban center outside both metropolitan metropolitan areas and the littoral of the country. areas and the littoral of the country. As to the constructive system of the buildings from the old urban center of the city of Viseu, As to the constructive system of the buildings from the old urban center of the city of Viseu, namely in what pertains to the vertical resisting elements, the abundance of granite stone makes this namely in what pertains to the vertical resisting elements, the abundance of granite stone makes the most common material with which to build masonry walls, as is common in the Northern Region this the most common material with which to build masonry walls, as is common in the Northern of Portugal. The granite used in the construction of the traditional masonry buildings of the old urban Region of Portugal. The granite used in