Static performance of prefabricated timber-concrete composite systems
2008 (English)In: Conference Proceedings, 10th World Conference in Timber Engineering, 2008Conference paper (Refereed)
Timber-concrete composite beams and slabs require interlayer connection, which provides composite action for the cross-section. A range of mechanical connectors is available on the market with an extensive variety of stiffness and strength properties, which are fundamental design parameters for the composite structure. Stiff and strong connection systems are highly desirable in order to achieve high composite action. At the same time, however, the connectors should be inexpensive, so as to make the composite beam an economically viable alternative to the traditional precast concrete and steel-concrete composite floor systems. This paper reports the outcomes of an experimental programme carried out on timber-concrete composite systems with prefabricated concrete slabs. The programme included shear tests to failure of different connection systems and 4-point bending tests to failure of five 4.8m long timber-concrete composite beam specimens. Based on the outcomes of the shear tests, two different connector types were selected for the full-scale beam tests: (i) steel tubes inserted into the concrete slab and screwed to the glulam beam, and (ii) single folded steel plates nailed to both sides of the glulam beam and welded onto a long punched metal plate embedded into the concrete slab. The new systems based on mechanical "dry-dry" connectors embedded into a pre-cast concrete slab have the advantage of not requiring pouring and curing of concrete on site. This will result in a significant improvement in the entire construction process by achieving higher quality while saving resources and simplifying recycling of waste.The beam specimens were ramp loaded to failure to assess the structural performance at ultimate and serviceability limit state. Mid-span deflection, applied load, and slip distribution along the beam length were monitored during the tests. The efficiencies of the new proposed connection systems, calculated by comparing the experimental results with the analytical limits of full and no composite action, were found to be in the same range as for connections with cast-in-situ concrete slabs. Some improvements such as a larger number of nails or larger diameter nails or screws are possible for the connection with metal plates nailed to the glulam beam in order to increase the composite action achievable by the system.The experimental load-displacement curves and slip distribution along the beam length were compared with the outcomes of a numerical analysis performed using a uniaxial finite element model purposely developed for timber-concrete composite beams. The actual shear force-relative slip measured in the shear tests were implemented in the software. Very good agreement was found, enabling the use of the program for parametric studies aimed to extend the experimental results to composite beams with different geometrical and mechanical properties. The use of the analytical formulae suggested by Ceccotti in accordance with the Eurocode 5 was found to provide acceptable accuracy for the design of the composite structure. In conclusion, the new developed composite systems based on the use of concrete slab prefabricated off-site and connected on site with timber beam can represent a viable alternative to the traditional composite systems with cast-in-situ concrete topping, with similar efficiencies achievable but all the advantages of the prefabrication.
Place, publisher, year, edition, pages
Research subject Timber Structures
IdentifiersURN: urn:nbn:se:ltu:diva-31775Local ID: 60d59770-d103-11dc-9ad7-000ea68e967bOAI: oai:DiVA.org:ltu-31775DiVA: diva2:1005009
World Conference on Timber Engineering : 02/06/2008 - 05/06/2008
Godkänd; 2008; 20080201 (elzluk)2016-09-302016-09-30Bibliographically approved