Influence of the Construction Method on the Long-Term Behavior of Timber-Concrete Composite Beams
Publication: Journal of Structural Engineering
Volume 141, Issue 10
Abstract
Timber-concrete composite beams (TCCs) are made from a concrete topping fastened to a timber beam. Different methods can be used to construct the TCCs. The concrete topping can be either poured on the timber beam with preinstalled connectors or prefabricated off-site and then connected to the timber beam. The timber beam can be shored during assembling with the concrete topping or left unshored. The use of the shored construction is usually recommended as a way to reduce long-term deflection; however, it is costly. This paper investigates the influence of the construction method on the long-term behavior. A previously developed rigorous uniaxial finite element (FE) software has been first validated on some long-term tests performed in Sweden on TCCs with prefabricated concrete slabs and different connection systems. The FE model has then been used to carry out some analyses where the deflection in the long term has been compared with the same TCC constructed in different ways. Parameters investigated include the mode of construction of the concrete slab (prefabricated off-site or cast in situ), the assembly of the composite beam (with shored or unshored timber beam), the storage time of the concrete slab, and the time between the end of construction and the application of the live load. The outcomes of this numerical study indicate that by prefabricating the concrete slab it is possible to reduce the long-term deflection, particularly when the slab is stored for at least 28–56 days before it is connected to the timber beam and when the timber beam is shored for at least 1 day. In these cases, the effect of concrete shrinkage is reduced, as well as the instantaneous and delayed deflection due to the self-weight of the beam. Conversely, systems with concrete poured on the timber beam should be shored for a longer time (at least 7 days). Shoring the timber beam does not markedly change the increase in long-term deflection due to concrete shrinkage; however, it does raise the tensile stresses in the concrete slab during the period the shores are left in place, leading to the potential for cracking when stiff shear connectors are used and for long shoring times.
Get full access to this article
View all available purchase options and get full access to this article.
References
Amadio, C., Fragiacomo, M., and Macorini, L. (2012). “Evaluation of the deflection of steel-concrete composite beams at serviceability limit state.” J. Constr. Steel Res., 73(2012), 95–104.
Balogh, J., Fragiacomo, M., Gutkowski, R. M., and Fast, R. S. (2008). “Influence of repeated and sustained loading on the performance of layered wood-concrete composite beams.” J. Struct. Eng., 430–439.
Bathon, L., Bletz, O., and Schmidt, J. (2006). “Hurricane proof buildings—An innovative solution using prefabricated modular wood-concrete-composite elements.” Proc., 9th World Conf. on Timber Engineering, Oregon State Univ. Conference Services, Portland, OR.
Brunner, M., Romer, M., and Schnüriger, M. (2007). “Timber-concrete-composite with an adhesive connector (wet on wet process).” RILEM Mater. Struct., 40(1), 119–126.
CEB (Comité Euro-Internat. du Béton). (1993). “CEB-FIP model code 90.”, Lausanne, Switzerland.
Ceccotti, A. (2002). “Composite concrete-timber structures.” Prog. Struct. Eng. Mater., 4(3), 264–275.
Ceccotti, A., Fragiacomo, M., and Giordano, S. (2007). “Long-term and collapse tests on a timber-concrete composite beam with glued-in connection.” RILEM Mater. Struct., 40(1), 15–25.
CEN (Comité Européen de Normalisation). (1999). “Timber structures–Glued laminated timber—Strength classes and determination of characteristic values.”, Brussels, Belgium.
CEN (Comité Européen de Normalisation). (2002). “Eurocode—Basis of structural design.”, Brussels, Belgium.
CEN (Comité Européen de Normalisation). (2004a). “Eurocode 2: Design of concrete structures—Part 1–1: General rules and rules for buildings.”, Brussels, Belgium.
CEN (Comité Européen de Normalisation). (2004b). “Eurocode 5–Design of timber structures—Part 1-1: General rules and rules for buildings.”, Brussels, Belgium.
Clouston, P., Bathon, L. A., and Shreyer, A. (2005). “Shear and bending performance of a novel wood-concrete composite system.” J. Struct. Eng., 1404–1412.
Deam, B. L., Fragiacomo, M., and Gross, L. S. (2008). “Experimental behavior of prestressed LVL-concrete composite beams.” J. Struct. Eng., 801–809.
Dias, A. M. P. G. (2005). “Mechanical behaviour of timber-concrete joints.” Ph.D. thesis, Delft Univ. of Technology, Delft, Netherlands.
Dias, A. M. P. G., Lopes, S. M. R., Van de Kuilen, J. W. G., and Cruz, H. M. P. (2007). “Load-carrying capacity of timber-concrete joints with dowel-type fasteners.” J. Struct. Eng., 720–727.
Fragiacomo, M. (2005). “A finite element model for long-term analysis of timber-concrete composite beams.” Struct. Eng. Mech., 20(2), 173–189.
Fragiacomo, M. (2006). “Long-term behavior of timber-concrete composite beams. II: Numerical analysis and simplified evaluation.” J. Struct. Eng., 23–33.
Fragiacomo, M. (2012). “Experimental behaviour of a full-scale timber-concrete composite floor with mechanical connectors.” RILEM Mater. Struct., 45(11), 1717–1735.
Fragiacomo, M., Amadio, C., and Macorini, L. (2007a). “Short- and long-term performance of the “Tecnaria” stud connector for timber-concrete composite beams.” RILEM Mater. Struct., 40(10), 1013–1026.
Fragiacomo, M., Balogh, J., To, L., and Gutkowski, R. M. (2014). “Three-dimensional modeling of long-term structural behavior of wood-concrete composite beams.” J. Struct. Eng.: Comput. Simul. Struct. Eng., A4014006.
Fragiacomo, M., and Ceccotti, A. (2006). “Long-term behavior of timber-concrete composite beams. I: Finite element modeling and validation.” J. Struct. Eng., 13–22.
Fragiacomo, M., Gutkowski, R. M., Balogh, J., and Fast, R. S. (2007b). “Long-term behavior of wood-concrete composite floor/deck systems with shear key connection detail.” J. Struct. Eng., 1307–1315.
Fragiacomo, M., and Lukaszewska, E. (2011). “Development of prefabricated timber-concrete composite floor systems.” ICE J. Struct. Build., 164(2), 117–129.
Fragiacomo, M., and Lukaszewska, E. (2013). “Time-dependent behaviour of timber-concrete composite floors with prefabricated concrete slabs.” Eng. Struct., 52(2013), 687–696.
Fragiacomo, M., and Schänzlin, J. (2013). “Proposal to account for environmental effects in design of timber-concrete composite beams.” J. Struct. Eng., 162–167.
Gutkowski, R., Brown, K., Shigidi, A., and Natterer, J. (2004). “Investigation of notched composite wood-concrete connections.” J. Struct. Eng., 1553–1561.
Gutkowski, R. M., Miller, N., Fragiacomo, M., and Balogh, J. (2011). “Composite wood-concrete beams using utility poles: Time-dependent behavior.” J. Struct. Eng., 625–634.
Karthik, M. M., Mander, J. B., and Rosowsky, D. V. (2011). “Lumber-boxed concrete structural system—Concept and preliminary analysis.” J. Struct. Eng., 1381–1389.
Kuhlmann, U., and Schänzlin, J. (2001). “Grooves as shear connectors for timber-concrete composite decks.” Proc., RILEM Conf. on Joints in Timber Structures, RILEM Publications, Cachan, France, 283–290.
Kuhlmann, U., and Schänzlin, J. (2004). “Time dependent behaviour of timber-concrete-composite structures.” Proc., 8th World Conf. on Timber Engineering, WCTE 2004, Finnish Association of Civil Engineers RIL, Helsinki, 313–318.
Lukaszewska, E. (2009). “Development of prefabricated timber-concrete composite floors.” Ph.D. thesis, Luleå Univ. of Technology, Luleå, Sweden.
Lukaszewska, E., Fragiacomo, M., and Johnsson, H. (2010). “Laboratory tests and numerical analyses of prefabricated timber-concrete composite floors.” J. Struct. Eng., 46–55.
Lukaszewska, E., Johnsson, H., and Fragiacomo, M. (2008). “Performance of connections for prefabricated timber-concrete composite floors.” Mater. Struct., 41(9), 1533–1550.
Morgado, T. F. M., Dias, A. M. P. G., MacHado, J. S., and Negrão, J. H. (2013). “Structural connections for small-diameter poles.” J. Struct. Eng., 2003–2009.
Newmark, N. M., Siess, C. P., and Viest, I. M. (1951). “Tests and analysis of composite beams with incomplete interaction.” Proc. Soc. Exp. Stress Anal., 9(1), 75–92.
Schänzlin, J. (2003). “Time dependent behavior of composite structures of board stacks and concrete.” Ph.D. thesis, Univ. of Stuttgart, Stuttgart, Germany (in German).
Skinner, J., Bregulla, J., Harris, R., Paine, K., and Walker, P. (2014). “Screw connectors for thin topping, timber-concrete composites.” RILEM Mater. Struct., 47(11), 1891–1899.
Toratti, T. (1992). “Creep of timber beams in a variable environment.”, Helsinki Univ. of Technology, Helsinki, Finland.
Turrini, G., and Piazza, M. (1983). “A technique for stiffness and strength upgrading of wooden floors.” Recuperare, 5, 224–237 (in Italian).
Weaver, C. A., Davids, W. G., and Dagher, H. J. (2004). “Testing and analysis of partially composite fiber-reinforced polymer-glulam concrete bridge girders.” J. Bridge Eng., 316–325.
Yeoh, D., Fragiacomo, M., Buchanan, A., and Gerber, C. (2009). “Preliminary research towards a semi-prefabricated LVL-concrete composite floor system for the Australasian market.” Aust. J. Struct. Eng., 9(3), 225–240.
Yeoh, D., Fragiacomo, M., and Deam, B. (2011a). “Experimental behaviour of LVL-concrete composite floor beams at strength limit state.” Eng. Struct., 33(9), 2697–2707.
Yeoh, D., Fragiacomo, M., De Franceschi, M., and Buchanan, A. (2011b). “Experimental tests of notched and plate connectors for LVL-concrete composite beams.” J. Struct. Eng., 261–269.
Yeoh, D., Fragiacomo, M., De Franceschi, M., and Koh, H. B. (2011c). “The state-of-the-art on timber-concrete composite structures—A literature review.” J. Struct. Eng., 1085–1095.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 141 • Issue 10 • October 2015
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Dec 19, 2013
Accepted: Dec 9, 2014
Published online: Feb 4, 2015
Discussion open until: Jul 4, 2015
Published in print: Oct 1, 2015
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.