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.

 

[stripez]

Can you fill the masonry voids with a non-combustible filler (used to use zonalite, but asbestos content, now) to give you the FRR of a 6" (5-1/2") concrete wall?

"asbestos content now?" but is it not asbestos is harmful for health? Any other non-combustible filler? that won't create moisture inside?

Also please clarify about stiffening of the wall mentioned by skeleton and Phameng.

Does it mean if I retain the metal frame and add masonry wall. The whole system is so stiff that the welded connections or joints can give way instead of ductile behavior if only masonry wall is used? But is it not masonry wall are not stiff either compared to solid concrete wall?

Or does it mean even if the metal frame is removed and only masonry blocks (or concrete) were used. This would affect the stiffiness of the building?

If it meant the latter, then I'd either try to add filler or remove the entire metal frame and just chip hammer the parapet and column and add rebars to make conventional masonry wall. Please clarify, to others too, so I know what to do. Thank you.

 

[stripez]

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To answer your question about reinforcing, yes, you can do that. You need special rebar with chemistry suitable for welding. In the us, it's ASTM 706, as opposed to the more common (in my market) 615. Drill and epoxy into the concrete. Be careful at the column - don't want to go cutting through your ties.

I'd be careful about doing this, though. As skeleton mentioned, it will stiffen that wall and could alter the behavior of the structure in an earthquake. You may be able to avoid securing the rebar at the top, and instead weld a series of vertical plates or angles that would keep the wall from falling over, but also allows the steel frame to deflect and move as designed.

What rebar at the top? you mean in the red label drawing of rebar welding to I-beam bottom flange? By the way, this was the actual connection above it. It was already so rigid.

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If I added solid concrete to all of this, it would become so rigid so I must remove all metal frame instead? It is difficult to remove all this framing.

 

[dik]

They used to use zonolite way back... not advocating the use of asbestos... check with masonry people to see if there is an equivalent fill. Could get 4 hours out of a filled 6" CMU... Don't know if there's something available, but could be a solution. Check what you can get with a 4" CMU...


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

-Dik

 

[stripez]

They used to use zonolite way back... not advocating the use of asbestos... check with masonry people to see if there is an equivalent fill. Could get 4 hours out of a filled 6" CMU... Don't know if there's something available, but could be a solution. Check what you can get with a 4" CMU...

Well. The purlin is 4" so the gap is 4". If I'd put fill, the outside cement board may not be able to contain it. What if I just put solid concrete to fill up the gap between the 2 boards? the C-Purlin can hold the concrete since the C shape can grip the hardened concrete, not unattached fill.

 

[dik]

You should be able to use it as a form...

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

-Dik

 

[stripez]

You should be able to use it as a form...

After the concrete hardened. How am I supposed to remove the 1.6mm thick 4x2" C-Purlin? remember the concrete will be set inside it. Also some of you comment it will stiffen the wall creating problem during seismic movement.

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The original parapet uses 6" Concrete Hollow Blocks. There is 1" plaster so total is 8" thick parapet wall. The metal frame was put on top of 2x2" angle bar bolted in the outer 4" edge of the 8" parapet wall.

 

[dik]

Sorry... didn't realise that you wanted it out... it's trickier...

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

-Dik

 

[stripez]

Why trickier?

After removing all the steel frame. Will chip off half the height of the 1 meter parapet composed of 6" CHB (Concrete Hollow Block). It's easy to chip it off, isn't it? Then will add about 400mm of rebar for development. I wonder if I should weld the new rebar to the old one or just tie it.

Also the 500x500mm column very big because it wasn't reduced as it reached the third store. It's supporting life metal roof only. Will drill it and put epoxy to the new rebar.

Has anyone tried anything like this?

 

[phamENG]

When I said steel frame, i wasn't referring to your studs (and very large studs they appear to be). I was referring to the beam above which I would guess is somehow connected to a diaphragm. If you attach the wall to the beam above in a way that doesn't allow slip, you'll be creating a shear wall whether you want to or not. And engaging those concrete columns could turn them into boundary elements and over stress them in an earthquake.

It sounds like you're trying to build this fire wall as a structural wall. It doesn't need to be. It just needs to be there to prevent the spread of a fire into this building from the next. You're in the Philippines, so I know seismic is a concern, but for such a small wall it seems odd that you'd need to chip away the concrete to expose the existing rebar and weld it off to the beam above. Just seems like...a lot. What are your actual forces at the concrete to proposed masonry interface and at the beam above?

 

[Sesha13]

hi

I m recently engaged in to project where design the steel Mainframe for drill rig (Epiroc). Frankly, I have no idea how to start and finish, I know we should go with beams to support this kind of high load-bearing condition (40000kg approx.).

I haven't worked on support or structure to bear a 40-ton weight before. Moreover, I need a clear picture of design considerations, stress calculations, welding process, and anything that involved in optimizing the design.

please give any reference of complete frame design with all calculations and considerations with forementioned.

I keen to learn everything even it takes time but I struggle to picturize what should I learn?! really appreciate it if someone guide me
thanks in advance

 

[stripez]

When I said steel frame, i wasn't referring to your studs (and very large studs they appear to be). I was referring to the beam above which I would guess is somehow connected to a diaphragm. If you attach the wall to the beam above in a way that doesn't allow slip, you'll be creating a shear wall whether you want to or not. And engaging those concrete columns could turn them into boundary elements and over stress them in an earthquake.

It sounds like you're trying to build this fire wall as a structural wall. It doesn't need to be. It just needs to be there to prevent the spread of a fire into this building from the next. You're in the Philippines, so I know seismic is a concern, but for such a small wall it seems odd that you'd need to chip away the concrete to expose the existing rebar and weld it off to the beam above. Just seems like...a lot. What are your actual forces at the concrete to proposed masonry interface and at the beam above?

No. The beam is not connected to any diaphragm. Right now it's not connected to anything except the cement board steel frame below shown in original picture (last picture below). But I need to put 500mm (0.5 meter) high firewall above the i-beam too.

This is the layout of the thin metal roof trusses, the cement board steel framing is the sides (or center of picture).

This is the column details. We didn't make it smaller to avoid changing the formworks. So the full 3 storey or 3 floor uses these column details.

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This is above it with the light metal roof.

If I add hollow blocks to the existing metal frame to create 4 hour fire rate firewall. I thought you meant it would be very rigid. But then the wall will still be very rigid unable to deflect during earthquake, isn't it?

If no need for the wall to deflect, and it will work. Then we can just add 12mm rebars shown in red in the following to support the new 6" hollow blocks? Any other ideas? It would take a lot of time to remove the entire metal frame. But if we remove it. We need to chip off the parapet wall and column to insert rebars to put 6' CHB (Concrete Hollow Block).

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Again this is above it (showing how the cement board frame is connected to the ibeam. This wasn't shown in photo above becuse the photo was taken before all top supports were welded years ago).

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All my projects just use CHBs on concrete beam with rebars sticking out the concrete beam supporting the wall. I haven't encountered layout like this so asking opinion. Thanks so much.

 

[dik]

I've submitted the following to the Masonry Contractors Association of America...

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?

Thanks, Dik Coates, P.Eng.

Even if not applicable, it's useful information to have... How is the firewall extended beyond the eaves? and how is drainage accomplished? Just a couple of thoughts... I should have added the MCAA has some excellent free webinars for PDH hours...

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

-Dik

 

[stripez]

Even if not applicable, it's useful information to have... How is the firewall extended beyond the eaves? and how is drainage accomplished? Just a couple of thoughts... I should have added the MCAA has some excellent free webinars for PDH hours...

There is no firewall extension yet in the eaves. I plan to put maybe 4" CHB on top on the i-beam about 500mtr (half meter) above the metal roof line. How do you put hollow blocks or masonry blocks on top of a steel i-beam?

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This is exactly the top portion of it showing the gutter, i-beam and cement board steel framing (showing the gap shown in upper portion of photo where I could theoretically pour filling, but the problem is the outer board may not be able to contain it from the pressure). If I'd put concrete blocks above the i-beam (it's only load). The gutter has to move inwards so maybe I'd cut some roofing (the green).

Right now. We just put metal flashing over the hole. Please show details how to put masonry blocks above I-beam. Do you just weld rebars on top of the i-beam. My concern is what if after few years, the welding gave way, then the walls won't be supported. A problem that doen't exist with concrete beam because the rebars are implanted deep inside. Thanks.

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[dik]

You can either weld rebar or add headed studs to the top of the beam to secure the CMUs.

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

-Dik

 

[stripez]

You can either weld rebar or add headed studs to the top of the beam to secure the CMUs.

Headed stubs are usually just welded to an I-beam surface. After say 20 to 30 years of constant sway of the wall, won't the head stubs welded part just gave way and the wall came crashing down? Has there been no incident like this anywhere? Doesn't the welded part even give way?

Also, and this is very important detail. Should I remove all the I-beam angle bar and flat bar supports to the cement board steel framing? Because if I have to remove it, then I have to remove all the cement board and steel framing. Can you put masonry or hollow blocks on this i-beam top with all these angle bar and flat bar holding the cement board steel frames?

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[dik]

THere are headed studs holding up a lot more than this 'little' parapet... they have a great history... Just noticed... I've thrown better welds than those, away... need to remove coating flux and touch up with zinc rich primer...

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

-Dik

 

[stripez]

THere are headed studs holding up a lot more than this 'little' parapet... they have a great history... Just noticed... I've thrown better welds than those, away... need to remove coating and touch up with zinc rich primer...

1. You forgot to answer this. Can you put masonry walls over the i-beam in picture with all the angle bars and flat bars connecting to the cement board steel frame? Like breaking the masonry blocks in two and put the pieces in sections or maybe a solid pour? If you forgot to answer this again. Hope others can address this major issues.

In my country. Our welding is so poor. Only poor people weld and their salary is $10 whole day. So I doubt the existing W8x21 can even support 0.5 meter of parapet. Here is the location of the i-beam splice and i'm doubting it hence if possible I don't want to remove the cement board steel frame to share or transfer the load from the i-beam to beams below which is made of solid concrete.

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2. And the reason the cement board steel frame was put was because the rebars on top of parapet was already cut, and also local structural engineers suggested years ago to chip off half of the existing parapet to epoxy new rebars as well as part of the column to put the new wall. But it was difficult to demolish half of it to add hollow blocks (or masonry walls). You have to demolish half of the wall to add the rebars and develop it, isn't it? Because we have have to do it if we remove the cement board steel frame.

Also the main reason we have to put 4 hour fire rating now is in case of fire, we don't want the flame to reach the neighbor's walls (right beside the building) or they could sue us big for structural damage.

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3. Also is the purpose of putting rebars inside masonry walls to make the walls straight and stiff and it HAS to be continuous to existing rebars inside? or can you add new rebars off center to old ones? Our structural engineers here just memorize the rules without analyzing what is really going on.

If you forget or can't answer the above issues completely (I number it 1 to 3 to make it easy to remember), hope others like PHAMeng can so I can have enough info to decide what to do. Thank you.

 

[phamENG]

1) You can put masonry on top of steel, though that splice may be questionable. It's just a matter of analyzing the beam to make sure it can take the load, and detailing a base for the wall. Is it going to be attached to anything above, or is it just going to be a parapet? If it's a parapet, it probably won't work in this application as you'd a)need a fixed connection between the masonry and steel and b)need to brace the steel beam for the torsion.

2) No. You don't have to demolish half the wall to add bars. Hammer drill and a tube of epoxy are your friends if you can get your hands on them. I have no idea what kind of products are available in your market, so I can't be of any help there.

3) Bars are put in masonry walls to reinforce them - make them stronger in bending and able to carry higher loads. Masonry has been built for thousands of years with no reinforcement at all...though that's likely not an option for you since you have to deal with earthquakes. That said, you just need the wall to hold together. You're building a non structural fire wall. The connections to the surrounding structure need only to keep the wall in place. You could probably accomplish that with some epoxied dowels, a strip of steel with studs welded to it that's bolted down to the concrete, 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.

I'm curious. You've started referring to "local structural engineers" as though you aren't one of them. What is your role in this?

 

[dik]

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

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

-Dik

 

[stripez]

1) You can put masonry on top of steel, though that splice may be questionable. It's just a matter of analyzing the beam to make sure it can take the load, and detailing a base for the wall. Is it going to be attached to anything above, or is it just going to be a parapet? If it's a parapet, it probably won't work in this application as you'd a)need a fixed connection between the masonry and steel and b)need to brace the steel beam for the torsion.

It's just a parapet wall 0.5 meter above metal roof line. Our fire requirement is to put extra 0.5 meter above the metal roof. About fixed connection between the masonry and steel. That's why we would weld headed stub to the i-beam and put masonry walls on top of it. This would address it, won't it? About bracing for torsion. My structural engineering friends don't even think of bracing for torsion. This is because we don't have any structural engineering schools. They just use Etabs or Staad to design without thinking of the physical principle. All structural engineers are just civil engineering graduate. I'm one too and and learning to design too. My experience is mostly reinforced concrete beam, column and slabs and they are continuous. Not treating isolated problem just as a single i-beam to support parapet only. So any idea how to brace the beam? Wait, since the cement board steel frame is welded to the i-beam every 0.6 meter distance, again picture shown here for emphasis. It is sufficient requirement for bracing it against torsion? Because we only have light metal roof and no diaphragm to brace against edge i-beam tension.

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2) No. You don't have to demolish half the wall to add bars. Hammer drill and a tube of epoxy are your friends if you can get your hands on them. I have no idea what kind of products are available in your market, so I can't be of any help there.

3) Bars are put in masonry walls to reinforce them - make them stronger in bending and able to carry higher loads. Masonry has been built for thousands of years with no reinforcement at all...though that's likely not an option for you since you have to deal with earthquakes. That said, you just need the wall to hold together. You're building a non structural fire wall. The connections to the surrounding structure need only to keep the wall in place. You could probably accomplish that with some epoxied dowels, a strip of steel with studs welded to it that's bolted down to the concrete, 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.

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The existing cement board steel frame has this strip of steel with stubs welded to it that's bolted down to the concrete. Again photo above. But then the bolt is only 2" deep. My structural friends said I have to demolish half other 1 meter parapet to access and existing rebars and weld to it. For them, the purpose of rebars is the strength of one particular vertical rebar. This is the problem when the country doesn't have any degrees of structural engineering. All are just civil engineers having experiences working in the field and just memorize the rules.

I'm curious. You've started referring to "local structural engineers" as though you aren't one of them. What is your role in this?

I already answered this above. Just a local structural engineer who asked more questions.