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Why Was The Notre-Dame Fire So Hard To Fight ?

PostPosted: April 16th, 2019, 5:00 am
by toucana
Fire visible in roof void above fan vault ceiling in nave

The fire at Notre-Dame in Paris yesterday has provoked a good deal of discussion as to quite why it was so hard for firefighters to tackle the blaze effectively at first.

The fire is reported to have begun within the vast wooden framed attic space above the quire and transept which was undergoing restoration work at the time.

The biggest problem, experts say, was accessing the wooden ceiling beams which formed the frame for the soaring roof. The attic contains thousands of oak beams, some of which date back as far as the 13th century.

Once the beams start burning, the stone exterior makes it harder for firefighters outside the building to get to the source of the flames. The internal stone fan vault ceiling also traps heat and smoke, preventing them from working inside either.

The Notre Dame's height also posed a challenge, providing extra oxygen for the fire to breath and complicating efforts to reach the flames.

"The fuel load is way up in the air, and the firefighters can't get to it quickly," said Glenn Corbett, associate professor of fire science at New York's John Jay College of Criminal Justice.

Aerial options like the one suggested by US President Donald Trump were also considered unrealistic.

"Perhaps flying water tankers could be used to put it out. Must act quickly!" Trump said in a tweet.

But according to Corbett, no plane pilot could drop water "exactly in that one spot moving several hundred miles an hour over it."

The French civil security agency, Securite Civile, said in an apparent reference to Trump's suggestion that any aerial water dumping could "weaken the structure of Notre-Dame and result in collateral damage to the buildings in the vicinity."

Corbett also ruled out the use of helicopters: "One of the issues you've got here, is that thermal updraft, that's a chimney effectively, you can't fly a helicopter in hot air. The air is so thin."

Once the burning 750 ton spire collapsed and crashed through the main roof and set the whole length of the building on fire, the most urgent priority was to stop the bell towers at the west end of the cathedral from catching fire. These towers house ten large bells. The tenor bell Emmanuel in the south tower alone weighs 13 tons, and there is another ring of eight bells in the north tower.

At one point French-fireighters were in a desperate battle to contain a fire inside the north tower. They warned that if the bell frame was consumed and those large bells tore free and fell, that the whole of the north tower would collapse with them.

In all probability the south tower would have been compromised and fallen as well, at which point a domino collapse of the entire external wall and flying buttress structure could have ensued to complete the demolition.

That much they were spared.

Re: Why Was The Notre-Dame Fire So Hard To Fight ?

PostPosted: April 16th, 2019, 11:31 am
by charon
Why Was The Notre-Dame Fire So Hard To Fight ?

Because, as I understand it, inside it was largely made of dry wood. And we don't know the cause of the fire yet.

Re: Why Was The Notre-Dame Fire So Hard To Fight ?

PostPosted: April 16th, 2019, 1:39 pm
by toucana
The void space between the fan vault ceiling and the external roof was filled with a supporting structure of timber beams equivalent to around 13,000 trees. That was the 'fuel load' referred to in the OP.

Everything else from the fan vault ceiling down to the ground is largely made of limestone columns and blockwork which is still standing (as shown in the photograph supplied).

The enormous stone arches and ribbed stone fan vault ceiling would have originally been constructed over massive pieces of wooden form-work that were subsequently demolished and removed by the masons and carpenters once the stone structure was fully complete, and was in equipoise, with the ceiling load evenly transferred to the walls and the external flying buttress system.

Rather remarkably, the Twitter feed of French News site BFMTV appears to be claiming that at least one of the famous Rose windows is still intact, and that at least one of the three great organs in Notre-Dame escaped the flames.