Experimental Assessment on Step Joint Timber Connections
Publication: Journal of Structural Engineering
Volume 148, Issue 9
Abstract
Carpentry joints are the traditional connecting media for timber elements. Among those, step joints are particularly important at structural size, because they are the most frequent solution to connect rafters and tie beams in roof timber trusses. The forthcoming version of Eurocode 5 will include, for the first time, provisions on its design. This paper describes the experimental investigation carried out to assess the safety and accuracy of the design formulae proposed in the literature and in some national standards on timber structures design. Although the behavior of double step joints is particularly aimed, given the scarce experimental information available on this configuration, single step joints were also investigated, intended to serve as a reference basis for the double-step case. It is also of interest to investigate how the load is shared between the two notches in the double-step geometries. To this end, an analytic procedure is proposed, based on the strains measured in the notches’ regions during the tests. Various test specimen groups were defined, whose dimensions favored one particular failure mode. The test setup was designed in order to simulate a rafter-to-tie beam connection in a timber truss. Besides the main strength tests of the step joints, side bending tests to EN 408 were also carried out in order to a better mechanical characterization of the used solid timber. Regarding the capacities, the results are in good agreement with the values provided by the formulae, and always on the safe side. The prevailing failure mode was as expected in most configurations, indicating the adequacy of the proposed design expressions. A procedure was proposed to determine the load share between the two notches in double step joints, but some setup detail changes are recommendable in order to improve its stability and reliability.
Get full access to this article
View all available purchase options and get full access to this article.
Data Availability Statement
All data, models, and code generated or used during the study appear in the published paper.
Acknowledgments
This work was cofinanced by the Regional Operational Programme CENTRO2020 within the scope of project CENTRO-01-0145-FEDER-000006 (SUSpENsE), and by the Operational Program Competitiveness and Internationalization R&D Projects for Companies in Copromotion, Portugal 2020, reference POCI-01-0247-FEDER-017867.
References
Branco, J., and T. Descamps. 2015. “Analysis and strengthening of carpentry joints.” Constr. Build. Mater. 97 (3): 34–47. https://doi.org/10.1016/j.conbuildmat.2015.05.089.
Branco, J., M. Piazza, and P. Cruz. 2010. “Structural analysis of two King-post timber trusses: Non-destructive evaluation and load-carrying tests.” Constr. Build. Mater. 24 (8): 371–383. https://doi.org/10.1016/j.conbuildmat.2009.08.025.
Branco, J., M. Piazza, and P. Cruz. 2011. “Experimental evaluation of different strengthening techniques of traditional timber connections.” Eng. Struct. 33 (8): 2259–2270. https://doi.org/10.1016/j.engstruct.2011.04.002.
Branco, J., M. Verbist, and T. Descamps. 2018. “Design of three typologies of step joints—Review carpentry joints.” In Proc., WCTE2006—9th W. Congress on Timber Engineering. Portland, OR: Oregon State Univ.
Brunner, M., and M. Schnüriger. 2007. “Timber-concrete-composite with an adhesive connector (wet on wet process).” Mater. Struct. 40 (Apr): 119–126. https://doi.org/10.1617/s11527-006-9154-4.
C4CI (Consultants for Construction Innovation). 2018. Dimmensionement à froid des as-semblages traditionnels bois conformement aux eurocodes. Paris: Comité professionnel de Développement des Industries Françaises de l'Ameublement et du Bois.
CEN (European Committee for Standardization). 1991. Timber structures—Joints made with mechanical fasteners—General principles for the determination of strength and deformation characteristics. Brussels, Belgium: CEN.
CEN (European Committee for Standardization). 2004. Euroc. 5: Design of timber structures—Part 1-1: General—Common rules and rules for buildings. Brussels, Belgium: CEN.
CEN (European Committee for Standardization). 2012. Timber structures—Structural timber and glued laminated timber—Determination of some physical and mechanical properties. Brussels, Belgium: CEN.
CEN (European Committee for Standardization). 2016a. Structural timber—Strength classes. Brussels, Belgium: CEN.
CEN (European Committee for Standardization). 2016b. Timber structures—Cal-culation of characteristic 5-percentile values and acceptance criteria for a sample. Brussels, Belgium: CEN.
CEN (European Committee for Standardization). 2017. French contribution for traditional carpentry joints. Brussels, Belgium: CEN.
CEN (European Committee for Standardization). 2018. Structural timber—Determination of mechanical properties and density. Brussels, Belgium: CEN.
CNR (Consiglio Nazionale delle Ricerche). 2018. Istruzioni per la Progettazione, l’Esecuzione ed il Controllo delle Strutture di Legno. Rome: CNR.
Descamps, T., and G. Guerlement. 2009. “Component method for the assessment of the axial, shear and rotational stiffness of connections in old timber frames.” In Proc., 9ème Congrès National de Mécanique. Casablanca, Morocco: Societé Marocaine des Sciences Mécaniques.
Descamps, T., J. Lambion, and D. Laplume. 2006. “Timber Structures: Rotational stiffness of European standardized approaches.” In Design of connections in timber structures—A state of the art report by COST FP1402/WG3. Aachen, Germany: Shaker Verlag.
DIN (Deutsches Institut für Normung). 2008. Design of timber structures—General rules and rules for buildings—Chapter 15: Carpentry connections for structural timber elements. Berlin: DIN.
Ministerio de la Vivienda. 2019. Código Técnico de la Edificación (CTE): Documento Básico SE/M—Seguridad Estructural—Maderas—Apartado 8.5—Uniones tradicionales. Madrid, Spain: Ministerio de la Vivienda.
Palma, P., and H. Cruz. 2007. “Mechanical behaviour of traditional timber carpentry joints in service conditions -results of monotonic tests.” In Proc., 16th Int. Symp. from Material to Structure—Mechanical Behaviour and Failures of Timber Structures—Int. Council on Monuments and Sites (ICOMOS). Paris: International Council on Monuments and Sites.
Palma, P., H. Garcia, J. Ferreira, J. Appleton, and H. Cruz. 2012. “Behaviour and repair of carpentry connections—Rotational behavior of the rafter and tie beam connection in timber roof structures.” J. Cult. Her. 13 (Sep): 64–73. https://doi.org/10.1016/j.culher.2012.03.002.
Parisi, M., and C. Cordié. 2010. “Mechanical behaviour of double-step timber joints.” Constr. Build. Mater. 24 (Jan): 1364–1371. https://doi.org/10.1016/j.conbuildmat.2010.01.001.
Parisi, M., and M. Piazza. 2000. “Mechanics of plain and retrofitted traditional timber connections.” J. Struct. Eng. 126 (12): 1395–1403. https://doi.org/10.1061/(ASCE)0733-9445(2000)126:12(1395).
Parisi, M., and M. Piazza. 2002. “Traditional timber joints in seismic areas: Cyclic behaviour, numerical modelling, normative requirements.” Eur. Earthquake Eng. 1 (26): 40–49.
Parisi, M., and M. Piazza. 2007. “Restoration and strengthening of timber structures: Principles, criteria and examples.” Pract. Period. Struct. Des. Constr. 12 (4): 177–185. https://doi.org/10.1061/(ASCE)1084-0680(2007)12:4(177).
Parisi, M., and M. Piazza. 2008. “Seismic strengthening of traditional carpentry joints.” In Proc., 14th WCEE—World Congress on Earthquake Engineering. Tokyo: International Association for Earthquake Engineering.
Parisi, M., and M. Piazza. 2013. “Carpentry joints in earthquake conditions.” Ingegneria Sismica 30 (4): 54–71.
Parisi, M., and M. Piazza. 2015. “Seismic strengthening and seismic improvement of timber struct.” Const. Build. Mater. 97 (May): 55–66. https://doi.org/10.1016/j.conbuildmat.2015.05.093.
SIA (Swiss Society of Engineering and Architecture). 2003. SIA 265-Timber structures. Zurich, Switzerland: SIA.
Siem, J., and A. Jorissen. 2015. “Can traditional carpentry joints be assessed and designed using modern standards?” In Proc., SHATIS 15—Structure Health Assess Timber Structure, edited by J. Jasienko and T. Nowak. Wrocław, Poland: Wroclaw Univ. of Technology.
Šobra, K., C. Ferreira, M. Riggio, D. D’Ayala, F. Arriaga, and J. Aira. 2015. “A new tool for the structural assessment of historic carpentry joints?” In Proc., SHATIS 15—Structure Health Assessment Timber Structure. Wrocław, Poland: Wroclaw Univ. of Technology.
STEP-Eurofortech. 1995. STEP 1—Timber engineering. Zwolle, Netherlands: Centrum Hout.
Villar-García, J. R., J. Crespo, M. Guaita, and M. Moya. 2018. “Experimental and numerical studies of the stress state at the reverse step joint in heavy timber trusses.” Mat. Struct. 51 (18): 17. https://doi.org/10.1617/s11527-018-1144-9.
Villar-García, J. R., M. Guaita, P. Vidal, and R. Argüelles. 2008. “Numerical simulation of framed joints in sawn-timber roof trusses.” Spanish J. Agric. Res. 6 (4): 508–520. https://doi.org/10.5424/sjar/2008064-345.
Villar-García, J. R., M. Guaita, P. Vidal, and F. Arriaga. 2007. “Analysis of the stress state at the cogging joint in timber structures.” Biosyst. Eng. 96 (1): 79–90. https://doi.org/10.1016/j.biosystemseng.2006.09.009.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 148 • Issue 9 • September 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Jan 6, 2022
Accepted: Apr 28, 2022
Published online: Jul 15, 2022
Published in print: Sep 1, 2022
Discussion open until: Dec 15, 2022
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.