Savings in fire design using stramit condeck HP decking

It has long been speculated that composite decks continue to contribute to slab strength during a fire. In a paper presented at the 2001 Australasian Structural Engineering Conference (ASEC), it was demonstrated that for Stramit Condeck HP® composite decking, the fire contribution is real, measurable and can be incorporated into slab designs.

This can result in significant cost savings in slabs.

The paper, entitled Fire Resistance of Stramit Condeck HP® Composite Slabs Incorporating Decking Contribution was written by Dr Jonathan Xie and Mr Chris Healy of Stramit Building Products. The paper combined fire test data from overseas work on various decks with specific tests on Stramit Condeck HP® decking carried out in Australia at CSIRO.

Fire tests on composite decking slabs have consistently reported that the temperature of the deck directly exposed to the fire is cooler than the furnace temperature. This is believed to be due to the heat sink effect of the concrete slab. It is also consistently reported that composite slab performance is much better than that predicted by the conventional design method, which ignores completely the contribution of the deck. This increase in performance is more marked in re-entrant style decks than trapezoidal decks.

Exceptional Performance

Full-scale and pilot fire tests on Stramit Condeck HP® composite slabs have shown exceptional performance. This is because of the fully enclosed re-entrant rib shape that can be seen in the illustration.
Steel retains some residual strength in a fire, even up to temperatures above 800°C. More commonly, contribution from steel is limited to temperatures below 600°C. For a two-hour fire test the maximum rib temperature recorded on a Stramit Condeck HP® decking rib is 533°C, well below the commonly applied limiting temperature of 600°C. For design purposes the reinforcement contribution of the Stramit Condeck HP® deck during a fire has been limited to those portions of the rib below that limiting temperature. In practice, the remainder of the deck will also contribute, but this is ignored

Potential Elimination of FER

The method of applying the benefits of Stramit Condeck HP® composite decking in a fire design is simple and is set out in the Stramit Condeck HP® Composite Decking Fire Design Supplement. Under some conditions it will be found that no additional fire emergency reinforcement (FER) will be needed. It will still be necessary to incorporate shrinkage and temperature mesh for crack control. This method has been reviewed and endorsed by fire experts at BRANZ.

These benefits have already been applied in Australian installations and overall FER savings of greater than 50% have been achieved.