Existing glass block above window - need fast lintel ideas 2

[Enable]

Here's the situation: the contractor was commissioned by the schoolboard direct to re&re windows on the ground floor. At present windows have been fabricated and they have started to install them. When they began to remove the existing windows they found that there was glass block above (hidden due to finishes), and that it was bearing directly on the window assemblies! There's no lintel or anything other than the frame to bring the load to grade. Severe deflection was noted in the block after they removed the first window.

Biggest thing is the original goal was to get students back into class by Jan 4th. Well, they have to for sure, but the goal was to have the work done by then so we're on a clock and hopefully can find something quick to do!

The windows vary in size but are 14-18ft long and appear to span between a CMU wall and a mid W-column. We are still waiting on approval to perform destructive openings so I can see all the existing framing / confirm member sizes. But I want to get ideas flowing so while things are open I have a good idea of what I might want to do (everything closed back up to get kids back to class come Jan 4th).

I'm a bit troubled given the size of the opening since it falls well outside the prescriptive tables in the code and if I run deflection calcs on a simply supported angle across the entire opening it is just a non-starter based on the info i've been provided in terms of amount of block, other loads, etc (I also am limited to maybe 3/8" angle or less since windows are already fabricated that close to the block). That said, I can potentially put vertical members in-between the windows since they come in individual pieces at 3-4ft length or so. I'd have them cover up the gap with sprayfoam / white flashing. My concern then would be out of plane suction wind loads. I'd need something more than just friction to rely on so I'd have to secure the angle to the block with some sort of anchor/stud/whatever. Does anyone have a good detail for glass block like that? I cannot recall a glass block job where I've ever had to tie into one and dont really know if there is anything strange with drilling into them (gut says there has to be)?

Note that the new steel lintel option will invariably involve shoring / needle beams / whatever and that'll take us into pretty extensive exterior repairs that were not planned for and the like. So while conventional and I suppose seemingly the simplest it wont be fast / cheap.

I also had the passing thought of carbon fiber wrapping the bottom blocks on inside/outside/underneath to effective make a beam that'll work for all directions. I'm not sure if carbon fiber wrap is suitable for a glass block substrate though and will need to put a call into the manufacturer. This idea mainly comes about because it would be cool to try lol if I am being honest

I'm not sure any of my ideas will work to get the students back into place by the deadline though, which is the biggest thing. If anyone has any wonderful ideas that can be done pronto / quick so the deadline can be met that would be awesome! If not, if you have better ideas but that take longer I'll take those as well

 

[phamENG]

Enable - the glass block has been covered, so it seems to me they don't care if there's glass block there or not - right? Why not demo the glass block, install a light gauge, built up header across the bottom with light gauge infill? Gyp on the inside, exterior finish appropriate to the architecture of the building and climate. You can even insulate it and improve the thermal performance of the building I would think.

EDIT: I know you said no exterior repairs, but with this you can finish the interior work first, and wrap up the exterior finishing while the classroom is in use.

 

[hokie66]

Agree with phamENG. Across the opening, a fascia truss, fabricated of light gauge or RHS sections, designed to take the out of plane loading and to receive the internal and external cladding.

 

[MIStructE_IRE]

I agree with the above. I’d do it in light gauge steel & insulate.

Whatever you do thought, you still need a lateral header to restrain the head of the new Windows when the wind hits. Maybe a SHS box section could span it? This box section could be the bottom chord of a very light truss if you need it.

Looks like brick externally at the moment. I’d try to avoid that for your new panels if you can in order to keep it light and simple. Perhaps a cladding or render on expamet/marine ply.

 

[HTURKAK]

I am not sure ... apparently the bldg has brick veneer exterior cladding.. If the windows are 14-18ft long , the glass block should not be bearing directly on the window assemblies..
Will you please post some exterior pictures ?..

Let me tell my guess ; The bldg has brick veneer exterior cladding and interior glass block only above the windows ,doors and masonry block work under the windows and the glass block only for decorative purpose ( second picture glass block is not transparent...)
I would suggest , take out one of the existing window frame ( if modular pieces ) or partially demolish to see if the window frame supporting the glass wall or the lintel detail . Probably you will see a common lintel for exterior brick veneer and glass block work ..

 

[Ron]

Agree with phamENG....light gauge truss is a good solution

 

[XR250]

Remove the block, add tube steel or light gage kings between the windows up to the roof framing to take the out-of-plane.
Then you only need very small headers.

 

[Enable]

Thanks team. I had already thought about that but decided against is due to a confluence of factors, such as: not in my client’s wheelhouse (I work for the contractor), timelines, more invasive and I’ll get into asbestos abatement since the glass is support for a ceiling asbestos finish above the one you see, and I am not really an EOR on this and such surgery ought to be coordinated via the boards design team.

I will throw it out as an option but at that point my client may not be the one doing it / won’t be me QBing it (which I might be okay with since it means I can get out of the city for Christmas!!).

HTURKAK: I’m going to have them remove the end windows so I can fully take a look at the head/jamb conditions to confirm. However, from what they said there was noticeable deflection (in the inches) when the window was first removed. Honestly…I wouldn’t put it past them to have built the block on top of the window. I’ve seen it done before with typical CMU though never with glass block and not with such spans.

MIStructE_IRE: I believe it's brick for the most part but at the glass block it's metal cladding. So strapping with ply & redoing something won't change the aesthetic too much, which is a bonus for the re-do in CFS option.

 

[phamENG]

In that case, can you work a steel angle in between the glass block and the head of the window? I'm guessing not, but if you could maybe there's a way you could put one in from both sides and then use flat bar to weld up a truss in the field on both sides. Can't say I love it, but it could work...

 

[Enable]

Definitely a neat idea, but that kicks me back to needing to get to the roof level framing which involves abatement. Pic below shows the old ceiling on top of the new one. I've been told that according to the designated substance report it contains asbestos, and since this is a school you would definitely be into type 2/3 abatement. And if that is the route we travel I think we all agree CFS with block removal is the way to go. Wouldn't be that much more to go full monty. With the CFS route it is also possible to do removals / install entirely from outside and perhaps eliminate abatement needs...though would not bet on that.

I do agree with everyone that it only makes sense to do it the CFS way. The assembly is absolutely horrid (as it is) from an energy efficiency perspective and now I'm talking about adding additional steel thermal bridges. That said, I absolutely need an option more oriented towards my client and so that leads to a steel angle with intermediate support. It also has the advantage of being cheaper. I'll probably offer up both at this point and just remark that both are invasive but only one has the opportunity for massive energy efficiency gains.

No matter what I am coming to the conclusion that timelines are shot though. I was hoping someone here might have some Christmas magic!

EDIT - Maybe I lied about phamENG's idea needing to get to roof level framing. Could perhaps do it in the cavity between old/new ceilings as long as I can get to the supports in some way. Going to revisit my thoughts on this.

 

[phamENG]

Lied is a bit strong...

But yeah, no need to go all the way to the roof as long as you can get sufficient depth below your toxic ceiling. Just need to be able to get a decent anchorage - that'll be the tough part. The interior CMU is probably 6" max and hollow, and the exterior is a brick veneer...

 

[MIStructE_IRE]

All these fancy ideas aside - kids won’t be back in by 4th Jan. I’d defer this until next Summer.

 

[dflva]

In your second photo, there is a thin horizontal white band between the glass blocks and the top of the window frame. What is that? Perhaps it is a steel plate with hangers placed between the glass blocks?