Special Feature
Insulating Properties of Timber Research has shown that timber used as large structures in buildings perform better during a fire compared with steel or concrete.
This is because steel will buckle and concrete will crack and crumble under high temperatures. Thick timber columns on the other hand, will initially ignite but the charring of the wood takes place at an extremely slow rate due to wood’ s inherent properties to naturally insulate in a fire. The charring of the outer layers of wood cuts off the oxygen supply and this effectively slows down the burning of the deeper layers of timber.
A detailed Fire Test Report published by Stora Enso Building and Living on 1 May 2014 shows that CLT buildings will maintain their structural integrity in construction site fire scenarios due to the material’ s limited charring rate. Massive engineered timber products such as glulam and CLT have a slow charring rate, allowing the building to maintain its structural integrity in a fire.
Another study found that there was no evidence at all of the difference in distribution of the size of fires between timber-framed buildings and those made of steel and concrete. Timber can also be treated with special chemical substances before arriving on site which can make the material incombustible and fire retardant.
This is an important factor as it provides the building’ s occupants with sufficient time to evacuate safely.
The Proof is in the Burning On 31 December 2012, a fire started in a strip mall in Salem, Oregon, shortly before midnight. The fire spread fast and destroyed everything except the glulam beams within the building. After the fire, the glulam beams were still so sound that the fire-fighting crew had to use their backhoes and bulldozers to break the beams in half to continue with their task.
Several experiments have shown that glulam beams consistently outperform other leading materials in fire resistance tests. The average building-fire temperature ranges from 700 °-900 ° Celsius. Steel weakens dramatically when the temperature is above 230 ° Celsius, retaining only about 10 % of its strength at 750 ° Celsius.
Studies have shown that within just 10 minutes of a fire, steel loses over 50 % of its structural properties.
Wood, on the other hand, only ignites at about 260 ° Celsius. Once heavy timber ignites, it chars at an incredibly slow rate of 0.635mm per minute *. Thus, in a 30-minute fire, only about 19mm of the exposed
Photo credit: Hüttemann.
Fire-resistance: Glued laminated timber beam of 16cm width and 40cm height before the fire test, after 30 minutes and after 60 minutes having been subjected to fire test according to DIN 4102( fire room temperature after 30 minutes 880 ° C and after 60 minutes 1,000 ° C).
GLULAM- Glued laminated load-bearing beams. Photo credit: Benox Timber.
LVL Curved Beams Photo credit: Frompo. surface of the glulam will be lost to charring while still retaining over 80 % of its strength.
Experts have concluded that although wood does burn, the contribution from the timber building materials to the fire load is usually small compared to the contribution of the building contents which constitute as the main source of fuel in a fire. It should be noted that large areas of wood-based surface linings in buildings can contribute to faster fire spread, though its effects can be mitigated by incorporating other design features into the building.
The emergence of modern engineered timber composites have enabled timber to stand tall – literally and figuratively speaking – against other construction materials such as steel and concrete. �
( Note: * Under the American ASTM E-119 fire exposure. Source: American Institute of Timber Construction.)
More information at www. mtc. com. my.
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