Development of Semi-Prefabricated Timber-Concrete Composite Floors in Australasia

Andy Buchanan

Professor of Timber Design, University of Canterbury, Christchurch, New Zealand

Massimo Fragiacomo

Associate Professor of Structural Design, University of Sassari Alghero, Italy

David Yeoh Eng Chuan

Ph.D. Candidate, University of Canterbury, Christchurch, New Zealand

Bruce Deam

Leicester Steven EQC Lecturer, University of Canterbury, Christchurch, New Zealand

Jenny Haskell

Research Assistant, University of Canterbury, Christchurch, New Zealand

Keith Crews

Professor of Structural Engineering, University of Technology, Sydney, Australia

An integrated research project on timber-concrete composite (TCC) floors in Australasia comprises of four primary objectives involving the University of Technology, Sydney; the University of Canterbury, Christchurch; and the University of Sassari, Italy together with several other industry partners. New applications of timber in multi-storey buildings are being sought by the timber industry in both Australia and New Zealand. Current development and testing of medium to long span flooring systems are highlighted. A semi-prefabricated timber-concrete composite (TCC) floor system that is economical, practical and easy to construct is proposed and four major phases of extensive investigations for short- and long-term involving full scale T-strip floor beams are described. The experimental results of phase one, short-term monitoring of beams are reported and compared with a uniaxial finite element model which was specially developed for long-term and collapse analysis of timber-concrete composite (TCC) beams. Overall, the validations were found to be within good accuracy except for some cases with acceptable experimental deviations. Other parameters observed were different construction variables and type of concrete.

The key component of a multi-storey timber building is the floor system. Pertinent performance requirements includes: (1) resistance to gravity load (strength limit state for out-of-plane loading), (2) control of vibration and deflection due to gravity load (serviceability limit state), (3) resistance to lateral load (strength limit state for in-plane loading), (4) control of deflection due to lateral load on the diaphragm (strength and serviceability limit state), (5) fire resistance, (6) acoustic separation, and (7) thermal insulation.

Several important advantages of timber-concrete composite (TCC) systems can be highlighted: (1) reduced self weight compared to precast concrete floor, (2) better acoustic performance compared to timber-only floors, and (3) ability to span 6 to 10m with minimum deflection as a result of high stiffness contributed by concrete topping. A semi-prefabricated floor system is currently under investigation at the University of Canterbury. The feature of this solution for multi-storey timber building is the prefabrication, ease of transport and erection due to the low self-weight. The crucial component is the connection system, which must be strong, stiff and economical.

References

Yeoh D., Fragiacomo M., Aldi P., Mazzilli M, and Kuhlmann U., “Performance of Notched Coach Screw Connection for Timber-Concrete Composite Floor System”, Proceedings, 10^th World Conference on Timber Engineering 2008. Miyazaki, Japan, 2008.

Fragiacomo M., Yeoh D., Davison R., and Banks W., “Chapter 25: Timber Flooring.” In: Buchanan, A. Timber Design Guide, Wellington: New Zealand Timber Industry Federation Inc., 2007, pp. 275-288.

CEN Comite European de Normalisation, “Eurocode 5: Design of timber structures - Part 1.1: General rules and rules for buildings”, EN 1995-1-1, Brussels, Belgium, 2004.

Comité Euro-International du Béton, CEB Bull. No. 213/214: CEB-FIP Model Code 90, 1993, Lausanne, Switzerland.

Fragiacomo M., “A finite element model for long-term analysis of timber-concrete composite beams”, Structural Engineering & Mechanics, Vol. 20, No. 2, 2005, pp. 173-189.

Toratti T., “Creep of timber beams in a variable environment”, Report No. 31, Helsinki University of Technology, 1992, Helsinki, Finland.

Buchanan A.H., Timber Design Guide (3rd Edition), New Zealand Timber Industry Federation, Wellington, New Zealand, 2007.

Raadschelders J.G.M., and Blass H., Stressed skin panels, Timber Engineering STEP 1, First Edition, Centrum Hout, The Netherlands, 1995, pp. B10/1-B10/10.

Gerber C., Crews K., and Sigrist C. "Predicting performance and designing stressed-skin panels - an Australian perspective", 19^th Australasian Conference on the Mechanics of Structures and Materials, Christchurch, New Zealand, 2006, pp. 1023.

Ceccotti A., Follesa M., Lauriola M.P., and Sandhaas C., “Which seismic behaviour factor for multi-storey buildings made of cross-laminated wooden panels?” Proceedings,

Ceccotti A., “Timber-concrete composite structures”, Timber Engineering STEP 2, edited by Hans Blass et al., First Edition, Centrum Hout, The Netherlands, 1995, pp. E13/1-E13/12.

CIB Working Commission W18-Timber Structures, Florence (Italy), Paper No. CIB-W18/39-15-4, 2006.

Deam B.L., Fragiacomo M., and Buchanan A.H., “Connections for composite concrete slab and LVL flooring systems”, Published online, Materials and Structures, RILEM. 2007.