scrubbedexpat142

Putting aside the heresy of using steel in a rebuild such as Notre Dame, the fire resistant properties of Glulam Vs steel are worthy of note, see below -

Pulaski

Because America is all about the most cost effective cheapest way to throw up a building!

All that proves is that plywood trusses are more fire resistant than pine and cheaper than steel.

That's a mighty big claim to make.

scrubbedexpat142

FFS Pulasski, we're talking about the restoration of a very historic building, not a throw up of Al's latest Toy Barn!

We are not talking about plywood trusses, we are talking about glued, laminated timber, which as you say are better fire rated than the equivalent steel, which, incidentally are more expensive than steel and (with reference to the "big claim") infinitely aesthetically preferable in a historic building. Glulam dead loads are (per m²) less than steel and supporting structural movement better absorbed by Glulam than by steel (on the one hand) while being more climatically stable (on the other).

Any other issues, just ask - in a former life I had 20 years experience with Glulam (also Jarrah & Keruing, but not oak).

scrubbedexpat099

Seriously unlikely they could find oak to replicate what was there, not visible anyway from below, then there is the issue which period you choose as your inspiration, if it was me I would go for the look and feel of what you want people to see and choose the best materials currently available, that was what has been done over the centuries.

scrubbedexpat142

Absolutely!

Oakvillian

The French need to talk to the Swedish Royal Navy. Back in the 1830s, a ten-year project was undertaken to plant 150 acres of oak on Visingsö, an island in Lake Vättern, to ensure a future supply of lumber for shipbuilding. The oak was interspersed with other species to keep them growing straight and tall. Now approaching 200 years old, they're perfect for structural timbers, and may well be able to provide most if not all of the roof structure for Notre Dame if required. Whether they're for sale or not is a different question, of course...

Pulaski

In an eniely concealed part of the building where no member of the public will ever see it, but we can all be comfortable that a steel beam is 100% guaranteed non-combustible
Do you know what plywood is? I'll give you a clue, it involves glue, and laminated timber. …. Agreed it is "engineered" in a way that sheet plywood isn't, but IMO it is UAF and should have no place in a historic building where it is visible to the public …. it looks like there should be a sign on the picture you posted: "Restoration sponsored by Ikea"
I didn't say that, you did, and I challenged you to support the assertion, and you have not yet done so. To be clear, I do not think that those composite beams are better than steel, especially given the width of Notre Dame nave that they will need to span.

scrubbedexpat142

Plywood is constructed from veneers, not solid timber.

You said -

"All that proves is that plywood trusses are more fire resistant than pine and cheaper than steel. "

As for span, check out the bridges constructed from Glulam.

And as for considering steel as aesthetically preferable in a historic building, that is just bizarre.

Pulaski

Yeah, and? Nobody said otherwise.
That's not what I said either!

I said [1] at Notre Dame the trusses are not visible, and [2] visible composite beams are ugly, really ugly, and IMO do not belong in a historic building. …. Of course in the real world there may be no alternative.

Just because I made statements [1] and [2] does not mean I think that visible steel beams are acceptable in an historic building. In fact from the statements I made you cannot use logic to determine what I think about exposed steel beams in historic buildings! …. But to clear up that question, I don't think they are acceptable.

scrubbedexpat142

Your stating that they are not visible & then claiming that Glulam beams are, in your opinion, ugly. Bit contradictory.

scrubbedexpat142

I would be surprised if they can't, in time, source sufficient oak.

Pulaski

Not at all two different things ….. I don't think Glulam beams are the best solution where the beams are concealed and resistance to fire is of paramount importance. …. The US article you linked stated that the composite beams are the "most cost effective" way to meet (minimum) fire code requirements, not that they are the best, most fire resistant solution.

I also don't think Glulam beams are the best solution where they are visible in an historic building, such as St George's chapel at Windsor.

scrubbedexpat142

Structural steel, under load, loses 50% of its strength at 560 Deg C.

We are not discussing St George's.

Pulaski

Why would they want to when it is concealed above the ceiling?

scrubbedexpat142

Just to try and keep the reconstruction in sympathy with the remaining structure & original design & construction.