Timber Structure Analysis
The Timber Research group is active in the field of structural analysis of both modern timber structures and existing structures belonging to the cultural heritage.
The use of timber as a construction material dates back to ancient history, with specific techniques differently developed within different regions. In the Mediterranean regions, specifically in Italy, timber was mainly used for roof and floor structures, whereas buildings assembled using only wood structure could be found only in the Alpine area.
Currently new engineerized wood materials, mainly glued laminated timber beams (glulam or GLT) and cross laminated timber panels (Xlam or CLT), allow wood to be used for long-span structures (large roofs, pedestrian and road traffic bridges) and multi-storey buildings. Also the problem of refurbishment of old timber structures is now of strong importance in our country, seen an increasing sensitivity towards the preservation of the historical heritage.
Recently another interesting opportunity was launched for new residential buildings. The possibility of obtaining multi-storey buildings with a structural skeleton entirely made of timber has aroused, in Europe, the interest of designers and customers, for commercial, residential, school buildings and social housing, thanks to the healthy living features of the material and a new attention towards the problems of environmental sustainability. Also in Italy some interesting buildings were recently built (e.g. new 10-storeys residential buildings in Milano), and several timber 3-storey buildings in L’Aquila, in the post-earthquake reconstruction, have proved to be very effective thanks to the short construction time.
Many researches, performed on the Italian market of wood products, demonstrate that a significant increase in the volume of timber used in construction will take place in the next few years, maintaining the constant trend presented since 2000, important reasons being the reduction in cost and construction time as a result of the prefabrication process, and the reduced self-weight compared with masonry and concrete, which allows a significant decrease of seismic actions. Furthermore, new types of architectural designs can developed, which are not necessarily related to the classical and traditional architectural forms. This fast development has occurred together with the issue of the new Italian Standards for Constructions, and the introduction of timber as building material in the new Italian Building Code, since 2008.
The group of research on timber engineering of DICAM, consequently, is strongly involved in many research activities but also in the education activity both in the Master Program of Civil Engineering and in the Doctoral School. There is also another field of interest, regarding the so-called life-long learning and the post-graduate courses offered in Italy in the field of timber engineering. This special educational activity is carried out thanks also to the support and the contribution of Industrial Associations for the promotion of wood construction in Italy and Austria (promo_legno and proHolz). Those actions are closely linked to another special activity, called “promo_legno risponde”, which offers an on-line help to the designers in order to solve problems related to structure, building physics, technology, material and certification (http://www.promolegno.com/risponde/).
There is a key-point to be underlined: DICAM is the only University Department in Italy able to offer a deep competence on timber engineering. That circumstance gives obviously optimum chances for the Department, even if the lack of competence in some other Italian Universities must be considered a weak point for timber industry. Indeed the timber research group has a strong capacity of attraction of industrial research projects, only limited by the research staff dimension. Research activity is now focused on the main issues, still open, regarding the behaviour and design of residential and commercial multi-storey timber buildings and the analysis and conservation of existing structures, with a special attention to the seismic performance. Among the in progress or recently concluded researches, they can be cited the research Green Model House GMH, developed for ITEA (Istituto Trentino per l’Edilizia Abitativa, TN) on the assessment and refurbishment of existing structures and, the research programs for the Italian Agency for Emergency Management (DPC) and for the ReLUIS consortium.
Many different research topics are considered at University of Trento, within the timber engineering world. Some of them are hereafter summarized:
- mechanical characterisation of timber elements using in-situ non-destructive tests;
- structural rehabilitation of timber structures;
- timber-based composite structures, particularly timber-concrete composite elements;
- static and seismic behaviour of traditional and innovative joints for new or existing timber structures, with a special accent on glued-in steel connections;
- strength, stiffness, ductility of traditional and innovative connections;
- timber housing.
The research is both theoretical and applied, this one conducted in close co-operation with the industrial world. Most of the projects are formulated with clearly defined objectives originating from problems identified in building, civil engineering, industrial world.
With regard to the first topic, is worth of note an interesting research financed by PAT with a post-doc position (DigiTimbeR research), regarding the possibility of characterization of structural timber on site, through non-destructive imaging of wood coupled with image analysis and CAD techniques to automatically detect those features that reflect information about the macroscopic heterogeneities in the material. Micromechanical tests and combination of x-ray and ultrasound tests are used to mechanically characterize heterogeneities. The aim is to implement so called “morphology-based models”, which are able to depict non-uniform stress distribution and failure initiation loci in the modelled timber elements. The effectiveness of the method is experimentally validated using novel approaches such as the digital image correlation (DIC).
Another topic of strong interest for building industry is that regarding timber-based composite structures and timber-concrete composite elements. The advantages of such strengthening technique for existing timber beams, for which this technology was originally developed, has been proved to be so relevant and valued by the designers and constructors that they have also adopted timber-concrete composite floor in new buildings. Many research projects have been developed, most of them directly funded by Industrial partners. Recently researches have been initiated on the so-called steel-timber hybrid structures.
The research topics presented above, are aimed at the detailed investigation of the following subjects:
- development of innovative automatic devices for non-destructive evaluation of the mechanical properties of timber elements;
- evaluation of the mechanical performances (strength, stiffness and ductility) of different types of connections, as well as of the influence of the connections on the global behaviour of timber structures;
- drafting of design recommendations;
- analysis of the static and seismic behaviour of traditional and innovative connections for timber elements, with particular attention to the moment-rotation behaviour of joints; splitting strength of timber beams loaded by dowel-type connections; behaviour of glued-in bars acting parallel and perpendicular to the grain;
- evaluation of the mechanical properties of timber exposed to fire.
One relevant application of the researches carried out is focused on the problem of refurbishment of old timber structures and of the preservation of the historical heritage. Strengthening of floors and roofs, belonging to ancient buildings, requires a deep knowledge of the material, of diagnosis techniques, of restoration technologies. The exploitation of some digital imaging techniques as complementary tools to be used during visual inspection of historical timber structures is deeply investigated. The research has direct implications in the field of conservation and restoration of architectural heritage. Case studies (floor beams of Belasi Castle, trusses of Thun Castle, Trentino) have been examined. Use of image analysis and computer graphic techniques for automatic detection of defects is a central topic also for the wood industry. Co-operation with MiCROTEC, leader in the field of opto-electronics for the timber processing industry, and with GraphiTech Foundation, Centre for Advanced computer graphics technologies, have been activated.
The researches on the structural assessment of timber structures at DICAM has led to an important application for timber poles used in the telephonic network, with the support and close co-operation of Cinetix srl. There are an estimated 8-9 million timber poles only in the Italian telephonic network. Asset management of wood pole utility structures aims at maintaining a high level of reliability against pole failure, while minimizing the number of unnecessary dismissed poles. There is a strong interest on the results of the research, expressed by Telecom Italia, British Telecom, Telefonica. Particularly, British Telecom visited in different occasions our Laboratories in order to focus the method for the specific pole arrangement in UK.
Regarding the problem of timber housing, timber research group of DIMS is currently cooperating on the Research Project “Chi-quadrato”, an Enterprise Consortium financed by PAT, involved in a research on residential timber building entirely made with wood (platform frame system). Within the final stage of the research, a full-scale 3-storey timber building was tested on the EUCENTRE shaking table (Pavia). The technical “know how” for this kind of structural system is very advanced in northern and central Europe, while, on other hand, the seismic performance of multi-storey buildings is not usually considered in design and productions processes. For this reason the mechanical performances of timber framed shear walls under seismic actions are under investigation through a wide experimental campaign, aimed to validate calculation model and connection details.
Another research project is worth of note. Within the framework of the European Project SERIES, a research activity named “TIMBER BUILDINGS” was proposed for Transnational Access to Earthquake Engineering Research Centre (NESDE) at LNEC (Laboratório Nacional de Engenharia Civil, Lisbon, Portugal), with the goal of verifying, through shaking table tests on full-scale models, the effects of earthquakes on different timber building systems. The project involved University of Trento (IT) as Lead User of Transnational Access, University of Minho (PT), University of Graz (AT)) and a number of Industrial partners. The research was focused on timber housing systems frequently used in Europe: timber framed system, log house system, cross laminated timber system. Four full-scale buildings were tested at NESDE, Lisbon (one log-house building, two timber-framed buildings, one CLT system), in the period 2012-2013.
The strength of the group of research on timber engineering, is based also on a number of contacts with some important Partners (Universities, Research Institutions), with which there is a continuous and close co-operation, and some Industrial Partners, for which some of the research projects have been formulated.
- CNR – Ivalsa, S. Michele a/Adige, Trento
- Dept of Architecture and Civil Engineering, University of Bath (UK)
- Dept of Civil Engineering, University of Bristol (UK)
- Dept of Civil, Environ &Geomatic Eng, Faculty of Engineering Science, UCL London (UK)
- Dept of Civil and Environmental Engineering, Chalmers University of Technology, Göteborg (SE)
- Dept of Structural Engineering, Faculty of Engineering, Lund University (SE)
- Dipartimento di Meccanica e Aeronautica dell’Università La Sapienza, Roma (IT)
- Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Milano (IT)
- Faculty of Forestry & Environmental Management, University of New Brunswick (CA)
- Fondazione GraphiTech, Trento (IT)
- Heig-VD Haute école d’ingénierie e de gestion du Canton de Vaud, Yverdon (CH)
- Holzforschung Austria, Research institute and accredited testing and inspection body of the Austrian Society for Wood Research (ÖGH), Vienna
- ISISE Institute for Sustainability and Innovation in Structural Engineering, University of Minho, Braga/Guimarães (PT)
- Technische Universität München, Lehrstuhl für Holzbau und Baukonstruktion, München (DE)
The research on timber structures at University of Trento pays also attention to the technology transfer from Academia to industry: the academic spin-off TIMBER TECH (www.timbertech.it) was created in 2011, whose goals is structural analysis and the development of software for the design of timber buildings.
- Cinetix srl (Padova, IT)
- Chi Quadrato Network (Condino, Trento, IT)
- Coperlegno srl (Roma, IT)
- Legno Più Case SpA (Condino, Trento, IT)
- Microtec srl (Bressanone, Bolzano, IT)
- Rotho Blaas srl (Cortaccia, Bolzano, IT)
- Rubner Haus SpA (Chienes, Bolzano, IT)
- Rubner Holzbau SpA (Bressanone, Bolzano, IT)
- X-Lam Dolomiti srl (Villa Agnedo, Trento, IT)
Associations for the promotion of wood
- Assolegno – FederlegnoArredo FLA (Milano, IT)
- Habitech, Distretto Tecnologico Trentino scarl, Rovereto (Trento, IT)
- proHolz Austria (Wien, AT)
- promo_legno (Milano, IT)
Committees for Standards
- UNI – Normal Beni Culturali “Wood and wood materials”, responsible for Standard UNI 11138 “Cultural Heritage. Wooden artworks. Load bearing structures in buildings. Proposals for the preliminary evaluation, the design and the execution of works”
- CNR, technical document DT 201 “Guide for strengthening of timber structures through FRP systems”
- CNR, technical document DT 206 “Istruzioni per il Progetto, l’Esecuzione e il Controllo delle Strutture di Legno”
- C.S.ll.pp., Commission for monitoring new Italian standards “Norme Tecniche per le Costruzioni”
- UNI – CIS Commissione Ingegneria Strutturale, SC5 “Timber structures”
- CEN/TC 250 / SC 5 “Design of Timber structures”, Italian delegate
- RILEM Technical Committee 215-AST “In-situ assessment of structural timber”
- RILEM Technical Committee TC245-RTE “Reinforcement of Timber Elements in Existing Structures”
Funded research projects and European COST Actions
- CoDuLe, Strategie per un comportamento duttile del legno (Fondo Ricerca PAT, 2003-2005)
- PRIN, Tecniche diagnostiche e di intervento poco invasive e completamente reversibili per il consolidamento e il miglioramento sismico delle strutture lignee di edifici storici, (MIUR, 2007-08)
- DPC-ReLUIS, Progetto 2005 – 2008, Linea di ricerca 1, Valutazione e riduzione della vulnerabilità di edifici in muratura, Dipartimento Protezione Civile, Consorzio ReLUIS, 2005-2008
- DPC-ReLUIS, Progetto 2009 – 2012, Linea di ricerca 1, Edifici in muratura, centri storici e beni culturali, Dipartimento Protezione Civile, Consorzio ReLUIS, 2009-2012
- DPC-ReLUIS, Progetto 2014, Linea di Ricerca (Temi generali), Strutture in legno, Dipartimento Protezione Civile, Consorzio ReLUIS, 2014-2016
- DigiTimbeR (post-doc position financed by PAT
- Green Model House GMH (ITEA, Trento)
- Chi Quadrato Network (Condino, Trento)
- EU’s Seventh Framework Program [FP7/2007-2013], grant agreement n°227887 (SERIES)
- FPS COST Action FP1004 “Enhance mechanical properties of timber, engineered wood products and timber structures”, membri Management Committee
- FPS COST Action FP1101 “Assessment, Reinforcement and Monitoring of Timber Structures”, membri Management Committee
- FPS COST Action FP1402 “Basis of structural timber design – from research to standards”, membri Management Committee
Postdoctoral researchers and Doctoral Students
Recent selected publications
- Piazza M., Tomasi R., Modena R. (2005), Strutture in legno. Materiale, calcolo e progetto secondo le nuove normative Europee, ISBN 88-203-3583-2, Biblioteca Tecnica Hoepli
- M. Del Senno, M. Piazza, R. Tomasi (2004), Axial glued-in steel timber joints – experimental and numerical analysis, ‘Holz als Roh- und Werkstoff’, volume 62, n. 2: pp. 137-146
- Ballerini M., Rizzi M. (2007), Numerical analyses for the prediction of the splitting strength of beams loaded perpendicular-to-grain by dowel type connections, Materials and Structures, 40 (1), pp. 139-149
- Piazza M., Riggio M.P. (2007), Typological and structural authenticity in reconstruction: the timber roofs of the “Pieve” in Cavalese, ‘International Journal of Architectural Heritage: Conservation, Analysis, and Restoration’, 1(1), pp. 60 – 81
- Tomasi R., Zandonini R., Piazza M., Andreolli M. (2008), Ductile End Connections for Glulam Beams, Structural Engineering International SEI, IABSE, n. 18(3), pp. 290-296
- Branco J.M., Cruz P.J., Piazza M. (2009), Experimental analysis of laterally loaded nailed timber-to-concrete connections, Construction and Building Materials, 23(1): pp. 400-410
- Piazza M., Tomasi R., Crosatti A., Theoretical and experimental analysis of timber-to-timber joints connected with inclined screws, Construction and Building Materials, Volume 24, Issue 9, September 2010, pp. 1560-1571
- Branco M., Piazza M., Cruz P. (2010), Structural analysis of two King-post timber trusses: Non-destructive evaluation and load-carrying tests, Construction and Building Materials, 24(3), pp. 371-383
- De Amicis R., Riggio M., Girardi G., Piazza M. (2011), Morphology-based macro-scale finite-element timber models, Computer Aided Design, 43(1), p. 72-87
- Andreolli M., Piazza M., Tomasi R., Zandonini R. (2011), Ductile moment resistant steel-timber connections, SPECIAL ISSUE IN TIMBER ENGINEERING, Proceedings of the Institution of Civil Engineers – Structures and Buildings, 164(2), pp. 65-78
- Piazza M, Polastri A., Tomasi R. (2011), Ductility of Timber Joints under Static and Cyclic Loads, SPECIAL ISSUE IN TIMBER ENGINEERING, Proceedings of the Institution of Civil Engineers – Structures and Buildings, 164(2), pp. 79-90
- Branco J.M., Piazza M., Cruz P.J.S. (2011), Experimental evaluation of different strengthening techniques of traditional timber connections, Engineering Structures, 33(8), pp. 2259-2270
- Loss C., Zonta D., Piazza M. (2013), On estimating the seismic displacement capacity of timber portal-frames, Journal of Earthquake Engineering, 17, pp. 879–901
- Riggio M., Tomasi R., Piazza M. (2014), Refurbishment of a Traditional Timber Floor with a Reversible Technique: The Importance of the Investigation Campaign for the Design and the Control of the Intervention, ‘International Journal of Architectural Heritage: Conservation, Analysis, and Restoration’, 8(1), pp. 74-93
- Tannert T., Anthony R., Kasal B., Kloiber M., Piazza M., Riggio M., Rinn F., Widmann R., Yamaguchi N. (2014), In situ assessment of structural timber using semi-destructive techniques, Materials and Structures, 47, pp. 767-785
- European Patent “Special Device for the execution of on site hardness test on load bearing timber elements” (VR2000A000052 it, 01112073.0 eu)
- European Patent “Method of Manufacturing a Reinforced Wooden Beam and Reinforced Beam thus obtained” (VR2001A0000034 it, 02005324.5 eu)
- United States Patent Application No. US 2011/0218744 A1 (Sep. 8, 2011), Method and device for assessing the structural characteristics of installed supporting poles (priority data VR2008A000116, Oct. 22, 2008)
Selected PhD Thesis
- Tomasi R., “Timber elements characterized by concentrated or diffused ductility and pseudo-ductility: state of the art, development of innovative technologies”. PhD dissertation, University of Trento, Department of Mechanical and Structural Engineering, 2004
- Riggio M., “Morphological modelling of timber elements. An application of digital technologies for the assessment of timber structures”. PhD dissertation, University of Trento, Department of Mechanical and Structural Engineering, 2007
- Branco J., “Influence of the joint stiffness in the static and dynamic behaviour of timber roof structures: consequences of different strengthening techniques”. PhD dissertation, Double PhD degree University of Minho (PT) and University of Trento, 2008
- Polastri A., “Seismic behaviour of semi-rigid joints for timber structures”. PhD dissertation, University of Trento, Department of Mechanical and Structural Engineering, 2010
- Andreolli M., “Semi-rigid joints with glued-in bars for timber structures”. PhD dissertation, University of Trento, Department of Mechanical and Structural Engineering, 2011
- Loss C., “Direct displacement methodology for timber structures: a proposal to improve the current European Code”. PhD dissertation, University of Trento, Department of Mechanical and Structural Engineering, 2011