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56 Materials Jan/Feb 2024 FDM AsiA | www.fdmasia.com

solutions in this system. disassembly of the connector were demonstrated both at the
One of the early studies was conducted by Natterer, whose connection level and at the foor level.
applied solution was later extensively tested for further adoption
in construction by other researchers. Their proposed solution Challenges of DfD in TCC Floors
was a notch combined with a threaded steel bar. The steel The application of DfD in TCC foors is currently limited.
bar had a plastic sleeve around it and a plastic cap in the Identifying the actual reasons for this requires a comprehensive

concrete section and was glued in the timber section with survey across the supply chain and the construction sector.
an epoxy adhesive. However, some of the potential reasons that are relevant to
However, DfD was not the focus of either of these studies, TCC foors, in the opinion of the authors of this paper, are
and therefore, the ease of deconstruction was not evaluated. highlighted as follows:
Some of the solutions investigated by Boccadoro et al. using An important technical challenge in implementing DfD in
steel rods combined with a notch connector may also allow TCC foors is the lack of versatile deconstructable connection
for deconstruction; however, this was not tested in their study systems on the market. Most of the existing solutions in
as DfD was not their focus either. Thai et al. investigated a the literature have been designed only for a certain type of
TCC connection fabricated in the wet–dry system that could construction or for a certain foor confguration.

be deconstructed as well. In addition, often considerably stiff connectors are needed
The connection was made with a rectangular notch and to meet the structural design requirements, especially for
reinforced with two self-tapping screws. They demonstrated long-span TCC foors.
that their proposed system could be deconstructed even after Nevertheless, most existing deconstructable connections are
exposure to large loads. Pang et al. proposed a deconstructable less stiff than regular connections of the same confguration.
connector for the wet–dry system as well using round notch Therefore, a lack of versatile and stiff deconstructable connection
connections, however, without the use of screws. systems could become a driver for the designers to use a

regular connection system that cannot be disassembled.
Solutions for Both Wet–Dry and Dry–Dry Systems
A commercially available connector, named FT connector, Higher Initial Cost Compared to Regular Design
was designed to facilitate the prefabrication of TCC foors, Methods
especially in the dry–dry system. This connector has already DfD is, in general, more expensive than regular design
been used in practical applications. approaches. In the case of TCC foors, this could be due
It comprises an inclined plastic tube (fxed at 30° angle) with to the higher price of deconstructable connection systems
a steel washer in the concrete section through which a screw compared to the regular counterparts and the extra effort
can be inserted in the timber section. Gerber and Tannert tested needed in the design and/or the construction process.

the connector in the wet-dry system as well, although it showed The additional cost might be offset to some extent at the
less stiffness and higher residual slip than a regular screw. end of service life, considering the reduced waste and easier
A recent research project performed by the authors of this reuse of the materials. However, the initial increase in the cost
paper specifcally focused on developing solutions that could and related future uncertainties could still be discouraging for
allow for the use of DfD in TCC foors for both construction construction companies, especially when they can achieve
methods and a wide range of foor confgurations. The similar or even better mechanical properties with lower costs
mechanical performance and the ease of application and using regular design approaches.