Posted Wed Feb 11, 2009 8:34pm AEDT, By Brigid Andersen
Victorian bushfire survivors are already talking about going home. Even the survivors with nothing to return to seem eager to just get on with it.
But when they do go home, when they do rebuild, it will no doubt be done with new fire plans in place.
Debate has raged over whether residents should stay or flee when threatened by fires, or even if specially designed fire-proof bunkers could save lives.
Stories of survival have emerged, like that of Latrobe Valley resident, Steve Van Rooy, who survived the fire by taking shelter in a concrete bunker on his property.
Keith Crews is a professor of structural engineering at the school of civil and environmental engineering at the University of Technology in Sydney.
Professor Crews believes that bunkers, much like the one that saved Steve Van Rooy, could be designed and built in houses and communities in bushfire-prone areas to help save lives.
"In the past there has been some discussion with CSIRO about so-called fireproofing of houses and use of shutters and all above ground stuff," he said.
"But I don't think anything would have survived well above ground.
"I think even reinforced concrete would just explode with that sort of heat that was there."
Underground insulation
Professor Crews says that underground bunkers could be the answer to protecting people from fires like those Victoria has just witnessed.
"You would need something that is essentially underground because of the insulating quality of the earth," he said.
"Obviously you would need something over the top of that that's quite well protected.
"The next issue that I think you would have to consider is oxygen or air because when you get a fire storm like that it's got a tendency to suck up all the air that's there."
Professor Crews says the earth would act as a natural insulator from the heat of the fire and the bunker would not need to be too deep.
"The earth is a great insulator. Obviously you would have to give consideration to groundwater and all those issues, but I would assume that something like two to 2.5 metres, so essentially it was like a basement," he said.
Professor Crews says employing techniques similar to those used in building concrete bomb shelters would apply in developing a fire bunker.
Aesthetic design
However, he says with the use of different materials, fire bunkers would not need to look like bomb shelters.
"[Concrete] would be the first material that I would use. It would be a combination of concrete and other things," he said.
"One of the interesting things is that it would be possible in some cases to actually build something underground perhaps in concrete but you could actually have either concrete or timber, or a combination of the two.
Professor Ross says the burning properties of timber mean it can actually act as an insulator.
"When you get very thick sections of timber they don't burn, they char," he said.
"So what happens is that the outer layer starts to burn when it reaches about 1,100 degrees Celsius but then the carbon layer forms and insulating layer and then the char rate progresses at a known rate - usually about 0.6 of a millimetre per minute.
"So you could use a combination of materials like that so you could actually take advantage of the insulating value of timber as well as concrete to come up with something that might work well, but might look okay aesthetically."
Professor Ross also believes the design of underground car parks could be enhanced to offer communities a safe place to wait out bushfires in larger groups.
He says building fire bunkers could be something that becomes mandatory in parts of Australia.
"Before it becomes a legislative requirement you want to define the performance criteria really carefully so it actually accomplishes what you want," he said.
"The best way of doing that would be to engage with a cross-section of design professionals so you could have fire researchers, fire experts, but also building experts that are working together to come up with a solution."![]()
Victorian bushfire survivors are already talking about going home. Even the survivors with nothing to return to seem eager to just get on with it.
But when they do go home, when they do rebuild, it will no doubt be done with new fire plans in place.
Debate has raged over whether residents should stay or flee when threatened by fires, or even if specially designed fire-proof bunkers could save lives.
Stories of survival have emerged, like that of Latrobe Valley resident, Steve Van Rooy, who survived the fire by taking shelter in a concrete bunker on his property.
Keith Crews is a professor of structural engineering at the school of civil and environmental engineering at the University of Technology in Sydney.
Professor Crews believes that bunkers, much like the one that saved Steve Van Rooy, could be designed and built in houses and communities in bushfire-prone areas to help save lives.
"In the past there has been some discussion with CSIRO about so-called fireproofing of houses and use of shutters and all above ground stuff," he said.
"But I don't think anything would have survived well above ground.
"I think even reinforced concrete would just explode with that sort of heat that was there."
Underground insulation
Professor Crews says that underground bunkers could be the answer to protecting people from fires like those Victoria has just witnessed.
"You would need something that is essentially underground because of the insulating quality of the earth," he said.
"Obviously you would need something over the top of that that's quite well protected.
"The next issue that I think you would have to consider is oxygen or air because when you get a fire storm like that it's got a tendency to suck up all the air that's there."
Professor Crews says the earth would act as a natural insulator from the heat of the fire and the bunker would not need to be too deep.
"The earth is a great insulator. Obviously you would have to give consideration to groundwater and all those issues, but I would assume that something like two to 2.5 metres, so essentially it was like a basement," he said.
Professor Crews says employing techniques similar to those used in building concrete bomb shelters would apply in developing a fire bunker.
Aesthetic design
However, he says with the use of different materials, fire bunkers would not need to look like bomb shelters.
"[Concrete] would be the first material that I would use. It would be a combination of concrete and other things," he said.
"One of the interesting things is that it would be possible in some cases to actually build something underground perhaps in concrete but you could actually have either concrete or timber, or a combination of the two.
Professor Ross says the burning properties of timber mean it can actually act as an insulator.
"When you get very thick sections of timber they don't burn, they char," he said.
"So what happens is that the outer layer starts to burn when it reaches about 1,100 degrees Celsius but then the carbon layer forms and insulating layer and then the char rate progresses at a known rate - usually about 0.6 of a millimetre per minute.
"So you could use a combination of materials like that so you could actually take advantage of the insulating value of timber as well as concrete to come up with something that might work well, but might look okay aesthetically."
Professor Ross also believes the design of underground car parks could be enhanced to offer communities a safe place to wait out bushfires in larger groups.
He says building fire bunkers could be something that becomes mandatory in parts of Australia.
"Before it becomes a legislative requirement you want to define the performance criteria really carefully so it actually accomplishes what you want," he said.
"The best way of doing that would be to engage with a cross-section of design professionals so you could have fire researchers, fire experts, but also building experts that are working together to come up with a solution."
