Innovative Engineered Timber Building Systems for Non-Residential Applications, Utilising Timber Concrete Composite Flooring Capable of Spanning Up to 8 to 10m
This project has developed technologies for prefabricated structural systems constructed from engineered wood products for floors and building frames, suitable for buildings up to eight stories in height. The project included the design of a virtual multi-storey timber building, a review of commercial flooring systems, and the development of interim design procedures for timber concrete composite (TCC) floors. Compared with either solid concrete or timber floors, TCC floors provide an excellent balance between increased stiffness, reduced weight, better acoustic separation and good thermal mass.
Outcomes from the project have confirmed TCC floors as a viable alternative to conventional flooring systems. The life cycle analysis of the virtual timber building has highlighted the potential advantages of timber-based building systems for commercial applications. The project also resulted in the formation of the Structural Timber Innovation Company, a research company that will continue to develop timber building systems in non-residential buildings in Australia and New Zealand.
Australasian Conference on the Mechanics of Structures and Materials
Research Status
Complete
Notes
December 11-14, 2012, Sydney, Australia
Summary
Timber-concrete composite (TCC) beams are made up two materials, i.e. wood and concrete, which exhibit different behaviours under long-term loading. The time-dependent behaviour of TCC beam is not only affected by the long-term load but also driven by the variation of the environmental conditions such as temperature and relative humidity. In particular, the maximum deflection under service loads may govern the design requirement for medium to long span TCC beams subjected to heavy environmental conditions. For such structures, application of simplified methods adopted by different codes may lead to significant errors. Hence investigating the long-term behaviour of TCC beams subject to variable environmental condition is of great importance for designers and researchers. In this paper the research undertaken on long-term behaviour of TCC floors is critically reviewed and the recent findings are highlighted. The most important references in the literature were selected to provide more depth into the time-dependent performance of TCC structure.
Medium rise commercial and multi-residential buildings (up to eight stories) represent significant markets that the timber industry can potentially penetrate. This is possible with the availability of advanced engineered wood product and ‘new generation’ composite structures. From the mid 2000’s, the University of Technology, Sydney (UTS), in partnership with universities and industry key-players in Australia and New Zealand – overseen by Structural Timber Innovation Company (STIC) – has been active in investigating innovative structural systems that utilise timber and provide a competitive alternative to steel and concrete solutions.
Timber concrete composite (TCC) solutions have been gaining a lot of attention in Australia and New Zealand over the last few years. To address this emergence, researchers at UTS have focused on identifying and optimising TCC connections and outlining robust design procedure. This paper puts forward design guidelines that comply with Australian codes and give consideration for ultimate limit state (ULS) and serviceability limit state (SLS) design requirements. Fabrication provisions are also provided in order to secure a sound and successful implementation of TCC floor solutions.
Timber concrete composite (TCC) floor systems are relatively new to Australia and satisfactory performance requires a rigorous design procedure addressing both ultimate and serviceability limit states. TCC structures have a degree of complexity, since they combine two materials that have very different mechanical properties and respond in different ways to their environment. In addition, most TCC structures exhibit partial (not full) composite action.
There are several design procedures for TCC structures. Among these, the Eurocode 5 (EC5) procedure is relatively straightforward and has been successfully implemented in Europe. It uses a simplification for modelling the complex timber–concrete interaction known as the ‘Gamma coefficients’ method, which manipulates properties of the concrete member to predict the cross-section characteristics of the structure. This Guide presents a design procedure for TCC floor structures that is based on the Gamma method and AS 1720.1 Timber structures Part 1: Design methods.
The Eurocode 5 approach has been adopted as the underlying basis for the design procedures presented in this document; modified to comply with current design codes and practices in Australia. It comprises normative parameters for the strength and safety (ultimate limit state) and informative guidelines for appearance, deflection limits and comfort of users (serviceability limit states). While the latter must be defined by designers to meet the specific functional requirements of the floor under consideration, it is recommended that the serviceability guidelines in this document should be adopted as a minimum standard for TCC floors.
At the time of publication of this Guide, there is still uncertainty about some aspects of long-term deflection of TCC floors. As such, it is recommended that designers exercise caution when applying the design procedures contained in this document to floors exceeding 8 m in span, utilising the notched connections and crossed screws. This caveat restriction is due to a lack of research data at this stage to support the behaviour of floors and connections for spans exceeding 8 m. Some general considerations for manufacturing the notched connections are presented in this Guide.
