Adding a firewall to this metal frame 2

[stripez]

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Client needs to have firewall put since it is beside another building. The w8x21 I-beams above columns were already installed as well as 1.7mm thick vertical C-purlins spaced every 0.4 meters apart. The I-beam were to originally carry another wall on top of it but client changed his mind.

There is supposed to be double sided cement board with 9mm thick. But this doesn't have hours long fire rating.

My questions.

1. What modern materials can you use to put a firewall in it?

2. The original rebars protrusion above the concrete parapet wall and on side of each column was already cut before because owner thought there would be no roof or wall added but changed his mind. If we will use traditional masonry or hollow blocks as firewall. Can you just add rebars welded to the vertical c-purlins and I-beam above? How? Is this the only way to put masonry on it? Any ideas? Thanks.

 

[dik]

If the steel beam is in the firewall assembly, it should likely be rated, too...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[stripez]

It goes without saying... the structure has to be capable of safely supporting the new loading...

The building is designed for 5 storey with concrete roofdeck. But only 2 storey with roofdeck was built and the metal roof was added to the roofdeck making total of 3 storey only. For allowance.

About fire rated steel. Yes. Will wrap the ibeam with wire mesh and plaster it or even spray it with fire coating. This is after it is decided how to put 6" CHB first and the parapet, and whether to make use of the cement board steel framing perhaps able brace the i-beam for torsion when 0.5 meter parapet above metal roof line is added.

 

[phamENG]

Most of us just have civil degrees - there are only a handful of schools in the US that give you a piece of paper that says "Bachelor of Science in Structural Engineering". I just focused my civil in structural course work, got a job at a structural design/consulting firm, and threw myself into really learning and understanding as much of it as I can.

If the cement board and frame are doing nothing structurally, then your best bet is likely to remove them, drill and epoxy rebar into concrete beam, and build a concrete masonry wall that bypasses the W8 and goes to your required height. Weld an angle with the leg facing down on the bottom flange of the beam with long slotted vertical holes and attach that to the masonry - add a low friction washer if they're available. Don't worry about anchoring it to the columns. I'd leave a gap and fill it with a rated foam filler that meets your fire code req's, size of gap will be driven by amplified seismic drift.

As to exactly what you need to do to meet your local codes, I'm afraid I can't help you.

 

[stripez]

If the cement board and frame are doing nothing structurally, then your best bet is likely to remove them, drill and epoxy rebar into concrete beam, and build a concrete masonry wall that bypasses the W8 and goes to your required height.

What concrete beam where you referring to? As I mentioned in original message. There was an existing 6" CHB (Concrete Hollow Block) wall where the cement board steel frame was put on (see pic below). You mean I should demolish the existing 6" CHB? If not how do I access the concrete beam and drill and epoxy rebar?

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[phamENG]

Sorry - missed that - looks like cast in place concrete. The parge (or whatever coating it has) is remarkably smooth. That complicates things a little, but not much. If the bars were cut off roughly flush with what's there, then chipping a little around the existing rebar and using mechanical couplers could be a decent idea. But, that block wall is already cantilevering up to support the base of the existing wall, so it's probably ok to do it for masonry, too. Just make sure it's braced at the top where it passes the steel beam.

Think of it this way: you're replacing a largely self contained wall (steel "studs" and cement board) with a self contained masonry panel. You just need to detail the internal of the panel to be as strong as it needs to be to stay together, and then detail the connections. If you needed this to be a shear or bearing wall, things would be different, but you're not. Since I'm not in a high seismic area, this is the sort of thing I'd probably let the architect detail. A little different for you, but in the grand scheme of things not structurally critical.

 

[stripez]

This thread is about adding firewall to cement board metal frame. Hope Dik has replies from the Masonry Contractors Association of America when he wrote:

"There were provisions to use a fill material for hollow units to increase the fire resistance rating. In past, materials like zonolite (vermiculite) were used and a 6" filled hollow unit would provide over 4 hours of fire resistance. Due to asbestos issues, vermiculite is no longer used. Is there a similar product that can be used?"

NASA should have discovered something as thin as an inch but function similar to 6" CHB in having 4 hour fire rating, isn't it? They could have used something in the international space station or in the design of ICBM or nuclear silos. If not, why is such material impossible?

Also phamENG. With these redundant connection in the upper part of the cement board steel frame connecting to the I-beam. Assuming the welding is competent or strong enough. Couldn't I just add concrete to the steel frame? You wrote: "Just make sure it's braced at the top where it passes the steel beam.". You meant I wouldn't use the I-beam as brace at top in case I'd just add CHB and remove the cement board steel frame? Why?

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By the way. The picture of the existing CHB parapet is smooth because it is covered with waterproof membrane. Remember it was just roofdeck with 2 floors not done.

 

[dik]

Reply from the Masonry Contractors of America Association:

The fill material could be a variety of material, The key is what the CMU is manufactured with. If the 6" CMU is manufactured using sand and/or limestone aggregate you cannot reach a 4 hr equivalent rating. What you fill the cores with takes on the rating as the CMU. Full lightweight CMU with cores filled will meet a 4 hr requirement. A proper blend of sand and lightweight with filled cores may meet 4 hrs. The blend will have to be verified by an independent lab. Fill material can be practically anything that is fireproof itself. Perlite, sand, expanded clay aggregate and masonry cell fill (course or fine grout) are possibilities.
The Masonry Society has an excellent book on Fire Resistance of Masonry. Chapter 7 Section 722 covers calculated fire resistance in the IBC. I am attaching a NCMA TEK that covers the same subject. Please let me know what you decide.
Thank you for contacting MCAA. Our goal is to make sure that when masonry is designed and installed correctly the public has the best wall system available.
Be safe,



Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[stripez]

Thanks for the reference. I thought your question was infill materials between cladding in stud steel wall framing.

In all countries of the world. Is it requirement of every country that if the property is right next to each other and needs firewall. The firewalls always have to be concrete or concrete blocks and can't be shalf wall? In your pictur earlier. The tall building sides is not besides another building that is why it uses shalf wall.

I talked with the original designer. He didn't put solid masonry and instead use light framing all the way up to have more seismic resistance. He hadn't thought about the fire rating. So if we won't put the concrete firewall and no technology on earth can even come close to 3 hour fire rating that doesn't use concrete. Then it is not impossible we would just recommend the floor to be converted just to be roofdeck with cover. Meaning it wouldn't be used or occupied anymore.

 

[Harbringer]

There are lots of fire rated assemblies that aren't concrete.

Link

You're jumping through hoops about this when you really need someone local that does this. Try contacting a local commercial architect.

 

[stripez]

There are lots of fire rated assemblies that aren't concrete.

Kindly mention all of them. Masonry has existed for thousands of years. In this modern era where rover walks on mars, we should have fire assemblies that are also 4 hour fire rated like masonry. This should be number one priority of material scientists.

 

[Harbringer]

From the link I kindly provided in my previous post:
• 3/4" Sheetrock Ultracode Core gypsum UL Des U415, A-90
panels, on furring channel 24" o.c., over two System I
layers 3/4" Sheetrock Ultracode Core gypsum
panels, face layer joints finished
• 2-1/2" USG C-H Studs 25 gauge 24" o.c.
• 1" Sheetrock gypsum liner panels
– base layer over furring channel applied vertical

An expert probably can come up with other solutions. As I said you probably need to contact a local specialist in fire protection. No structural engineers that I know design fire-rated assemblies.

 

[stripez]

If the cement board and frame are doing nothing structurally, then your best bet is likely to remove them, drill and epoxy rebar into concrete beam, and build a concrete masonry wall that bypasses the W8 and goes to your required height. Weld an angle with the leg facing down on the bottom flange of the beam with long slotted vertical holes and attach that to the masonry - add a low friction washer if they're available. Don't worry about anchoring it to the columns. I'd leave a gap and fill it with a rated foam filler that meets your fire code req's, size of gap will be driven by amplified seismic drift.

PhamENG, I can't visualize your description "Weld an angle with the leg facing down on the bottom flange of the beam with long slotted vertical holes and attach that to the masonry - add a low friction washer if they're available. Don't worry about anchoring it to the columns."

How to put slotted vertical holes and what is the orientation? And what washer? Can you maybe draw it please?

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I found out that there were small objects inserted under the angle bar of the steel stud, the reason so rain water wouldn't be trapped and the angle bar rusted (in the photo, the welding part was cleaned and painted afterwards). Therefore I have to remove the entire steel stud because the bottom is not bearing uniformly on the existing CHB parapet. I may also remove half of the parapet to insert mechanical coupler to existing vertical reinforcement and insert new ones too.

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This is the detail above in the other side of wall (without top steel bracket).

We will put new 6" CHB, the height to the I-beam is 3 meters, and another parapet 1.4 meters height. So imagine 4.4 meters (14.4 feet) wall. Not only that, the I-beam will be 2" away from the new wall (not directly above CHB wall). So the wall at 3 meter height needs to be braced by the I-beam at its sides. What kind of masonry would have enough vertical reinforcement strength and how to create beam bond on the wall to brace it? Can others please share or suggest too the exact details? In my country. We either put concrete beam above wall (but not possible in my project) or put I-beam directly on top of wall. This is what other engineers do. But you know we can't put the I-beam directly on top of the 3 meter CHB because the I-beam was already put in placed and it can't support 1.4 parapet due to torsion in I-beam not braced by any diaphragm or rafter. Thanks.

 

[stripez]

The original designer of the additional floor is one of the biggest structural firms in the country.

http://www.rbsanchez.com/

They built 50 to 80 storey buildings and the metal roof i'm describing in this thread is just a 3 storey building with 0.5mm thin metal roof.

I talked to the head designer of the structural firm. He said they never brace a hollow block wall with I-beam beside the wall. It is always I-beam directly above the wall especially if there is another 1 meter parapet above it. And it is up to the contractor to coat the I-beam to make it fire resistant. I asked him what if the I-beam would have torsion from the parapet above it. He said the beam is designed to resist torsion.

I'd like to know if anyone of you has actually built a masonry wall with the i-beam at inner side bracing it at 3m height with another 1 meter parapet above the wall. Or a total of 4 meter high wall with the I-beam bracing it at the sides at the 3m height (for emphasis).

If none of you do it and it is not practiced elsewhere in the world, then I have few possibilities left.

1. To just build 3 meter high wall with the I-beam bracing it at the inner side with no parapet above it.
2. To remove all the $10,000 roofing and try to chip the top portion of column to construct a concrete beam.
3. To render the floor unoccupied or condemn it as uninhibitable.

The owner didn't follow the original plan of putting I-beam right above masonry wall because the roof contractor already welded the I-beam at the 8" inner side of column with base plate and owner just put cement board cladding for ease of construction. So now it's like we are going to replace it with original plan but the I-beam can't be moved to the edge right above Masonry wall anymore. So I have to consult with another structural firm about bracing it at the inner side. But most don't do it. I want to know how many percentage of you actually do it? 0.1%?

Please advise. Thank you.

 

[stripez]

This was supposed to be a separate thread how to connect new wall to the old slab but PhemENG himself commented in the new thread there was this old thread, hence no one replied to the new one. So let me put them here now.

I'll reword everything to make it brief and precise. First is there no problem putting 6" or 8" wall eccentric to the 12" concrete beam? Or do you put the wall at center of the RC beam? (this was old actual construction photo)

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I will remove not only the cement board steel framing but the entire 1 meter 6" concrete hollow blocks parapet underneath it. Then will put a new concrete wall instead. Better than masonry or concrete hollow blocks. Isn't it? This is the original slab.

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In the archive photo, column stirrups were inserted later. The reason we put the 8" stand at bottom is because it was originally a roofdeck and waterproof membrane is to be placed from slab to 8" of wall.

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Now my questions.

Can I insert the new dowel in between the existing 10mm rebars? Or should I only put mechanical coupler to old rebar? But then since I would demolish the entire parapet. Why should I put mechanical coupler, can I instead just lap and tie it with wire just like one does in all new construction with enough reinforcement development length?

What must be the size of the new rebars and how deep should it be drilled and epoxied to the concrete 8" stand underneath? Or should I remove the 8" concrete stand as well?

 

[stripez]

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Before putting a whole new concrete or masonry filled hollow blocks. I will let expert welders put plates all over the I-beam splices more than enough to strengthen and resist or brace the wall beside it (no load above the I-beam and no diaphragm at roof). Not only that. I'll surround each of all the 9 column tops with 4 pcs of 2 feet rectangular metal plates (all 4 sides, see green label in photo above) and welding them to the baseplate at top. Imagine a plate cap. I will make sure the concrete cone stress at anchor above is far from the anchors at the side plates. Or maybe I don't even have to put anchors in the surrounding new 4 plates because it can secure them from lateral movement already from all sides of the column, What do you think?

Has anyone seen anything or done anything like it? Please show some reference of baseplate caps put on such column top.

This is the 500x400mm column top details.

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[stripez]

summary: We don't have any bond beam blocks in the whole country, never used them before.

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What we use are only concrete hollow blocks exactly like the following:

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I re-read this thread. And finally understood why I didn't understand. It's because we don't use any bond beam blocks in the whole country. So I can't find any of them and no architects or structural engineers use them in the design.

Earlier in the thread. PhemENG and others assumed I had diaphragm above so warned me about creating shear wall. Then assumed my existing parapet is a concrete, so gave suggestions how to add the wall. Sorry for not making things clear at start. But my existing parapet where the cement board steel frame is resting is actually hollow blocks.

What I didn't make clear and I need to make clear now is we never have and never use any bond beam blocks. PhemENG wrote:

"I've even used steel angles bolted to the concrete below and then specified bond beam blocks with breakaway webs installed upside down and grouted solid to help with shear transfer".

We only used concrete hollow blocks like that described above. We never see an actual bond beam block before in our lifetime. Therefore without them. There may not be enough shear transfer to tie it at 3 meter height and then another 1.4 meter of parapet above, right? Please clarify.

That said. So without bond beam blocks or precast wall. There is no way to do that, bracing the wall to the I-beam, right? So we can decide what to do. Need international assistance for this. Thank you.