Can firewall include perimeter columns? 4

[Pixy]

A firewall is supposed to be constructed from the ground up. But can the perimeter main columns be considered part of the firewall?

If not, then for high storey building like 10 storey. How do they make the firewall?

 

[rapt]

As long as the columns are designed for the fire exposure.

 

[Pixy]

Usually columns were designed only for the moments, shear, axial load, ultimate moments and shear strength with standard concrete covers. This is to avoid more dead load and expenses.

Do you mean by columns designed for fire exposure to have much thicker concrete cover or just normal columns can all be part of firewall because it usually takes an hour for the rebars in ordinary columns to deform or the concrete to expand, contract and be destroyed?

Can you give example of columns designed for fire exposure?

 

[DBronson]

Pixy:

Assuming you're in the US, the definition of a fire wall (not fire partition) in the IBC states: "FIRE WALL. A fire-resistance-rated wall having protected openings, which restricts the spread of fire and extends continuously from the foundation to or through the roof, with sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of the wall." My understanding is that you'll need two columns - one on each side of the fire wall to meet this requirement.

Regards,

DB

 

[Pixy]

I'm not in the US. But we copied word for word the US codes. That's why I want clairify direct from the Americans (or code maker) because most architects, engineers, building officials here are confused.


So when you say foundation to the roof. Is this valid only for say 2 to 3 storey building? But how about 10 or 20 storey building. How can you make 20 storey fire wall extending continuously from the foundtion to the roof?

 

[JLNJ]

You might need a double wall. Or some jurisdictions allow for an extremely "smart" wall which holds on to the structure on the non-fire side and lets go of the fire side (usually through a type of fusible link).

 

[dik]

Generally with firewalls, the structure on one side has to be able to collapse without it affecting the firewall... Connection can be an issue.

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

-Dik

 

[rapt]

Pixy,

Columns are designed for fire using "deemed to comply" cover rules or in some cases by strength calculations (eg Eurocode allows this as an alternate design approach).

 

[DBronson]

Pixy:

Ive never had to deal with a very tall fire wall. The general approach is to use a single wall that is braced by the structure on both sides. The trick is to detail the braces as break-away connections, as Dik mentions. It sounds like you have a complicated project. I'd suggest getting a fire protection engineer involved to sort out these questions. Also, again I'll ask: are you certain you really need a firewall as opposed to a fire partition or fire barrier?

Regards,

DB

 

[hokie66]

The OP is asking about an exterior fire wall, not a fire wall separating adjoining spaces. The fire rating is all that counts in this case, and if the columns have at least the fire rating of the abutting wall, no problem.

 

[HTURKAK]

Having worked with different standards , i will try to respond OP's questions,


Mr. Bronson answered the definition of the firewall with wording in IBC and a big pink star for his approach... IMO, the perimeter main columns can be considered part of the firewall as long as having the same fire rating with firewall ..( SNIP II-01-02-85 defines fire rating 2.5 hrs fore firewall and the same rating for columns ..)
[quote
Usually columns were designed only for the moments, shear, axial load, ultimate moments and shear strength with standard concrete covers. This is to avoid more dead load and expenses.][/quote]

I disagree with you .. Refer to EC BS EN 1993-1-2,(Part 1-2: General rules — Structural fire design for steel structures ). and EC-2 Part 1.2 General rules —Structural fire design ( for concrete structures )

As far as i understand, your question is for a bldg . having more than 10 storey.. If you need a firewall to divide the plan to fire zones,( the plan big enough so fire zoning necessary ),IMO, you can provide EJ and firewall at one side and doubling the columns and beams at EJ and the columns both sides SHALL HAVE FIRE RATING mit firewall..

If you post the plan , proabbly you may get better responds..


My opinion only..

 

[Pixy]

I'm not designing any building. Just reviewing an old one. And I'm just driving around looking for even one Firewall that is independent wall but so far, can't find it.

I found out our Firewall is just fire wall (small letter and separate words) meaning wall that is fire rated. This is from a sketch by an architect of what fire wall in R5 residential classification mean.

In your place or code, what is your definition of Firewall? Is it just fire wall? What country needs those independent Firewall?

Also is the design (and especially the foundation ) of the independent Firewall more like retainer wall or shear wall? Please show me an example. Thanks.

 

[HTURKAK]

What is independent ? Not sure about your question .. Do you think the firewall is a seperate structure with seperate frame ?
The last picture you have posted is for a corner plot of attached bldgs and the sidewalls at property line shall be fire rated firewall . The same requirement is valid for the next bldgs..

Maybe it would be helpfull to look to the definition and requirements of firewall , Copy and paste from

- IBC 2018
FIRE WALL. Fully addressed in Section 706, one or more fire walls are building elements used to divide a single building into two or more buildings for the purpose of applying the allowable height, allowable area, and type of construction requirements of the IBC. In addition, a fire wall is selectively identified in the code as a means to serve a variety of purposes, including the use of horizontal exit separation as addressed in Section 1026.2.Starting at the foundation and continuing vertically to or through the roof, a fire wall is intended to fully restrict the spread of fire from one side of the wall to the other. Fire walls
are higher level fire-resistance-rated elements than both fire barriers and fire partitions.Because the concept of fire walls is to create smaller buildings within one larger structure,with the code regulating each small building individually rather than collectively, it is critical that a fire wall be capable of maintaining structural stability under fire conditions. If
construction on either side of a fire wall should collapse, such a failure should not cause the fire wall to collapse for the prescribed time period of the rating of the wall.

-EC 1992
1.5.2 Fire wall: A wall separating two spaces (generally two buildings) that is designed for fire
resistance and structural stability, and may include resistance to horizontal loading such that, in
case of fire and failure of the structure on one side of the wall, fire spread beyond the wall is
avoided.

- SNIP II-01-02-85

Summary for Russian text: The fire wall shall be supported on foundation and extend entire heght of the bldg, fire walls can be constructed on the frame of the bldg with non-combustible material .Fire walls shall extent min.60 cm above the roof attica.

I hope this post answers your question ..

 

[dik]

Are you talking an actual firewall or just a fire separation. Most firewalls have to extend beyond the structure.

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

-Dik

 

[Pixy]

HTURKAK and others,

HTURKAK wrote:

Fire walls shall extent min.60 cm above the roof attica.

Ok let us focus on this as this is my main concern, the 60cm firewall extension above the roof. But first let's be clear we are talking of firewall in this context:

But the existing building I'm analyzing has one roof much lower than the adjacent building. Or this is exactly the situation.

composed of 0.4mm thin metal sheet like this:

So questions.

1. If you put 60cm or even 100cm concrete parapet extending the firewall below the green roof (already existing) at the boundary with the higher wall building (separate owners). Would 60cm parapet helps in preventing spread of fire or is it not so significant as the fire can go up?

2. The metal roof is only 0.4mm thin, how long for an average home or office fuel load before the thin metal roof literally melts? Is it 15 minutes? 30 minutes? I need actual figure as I've been looking for this answer for years.

I actually researched about the different codes about it worldwide. We don't have code for this scenario where one building has much lower roof and I want to use common sense whether to remove 5 meter of the roof and make the floor below it unoccupied as it's extremely to make a competent 5 meter strip with FRR (fire resistance rating) that can work.

This is the illustration in other codes about this (from New Zealand):

Again what would be the behavior if you put 60cm or 100 cm (39 inches) parapet between them (or at the edge of the lower roof adjacent to the higher building)? And also won't the higher building has columns directly over the top of the roof of the lower building (the reference I read only mentioned "wall" and not "columns". the concern are the columns of the neighbor that can be damaged even by 30 minutes of fire which would render the entire building uninhabitable and millions of dollars of damages).


This is summary of what the different codes do (rest of countires don't have the provisions).

 

[Pixy]

This is the great reference about fire spread from lower roof that I read entirely.

https://www.branz.co.nz/pubs/research-reports/sr409/

But after hours of searching and even asking roof contractors, they don't know how long before a 0.5mm (0.02") metal roof can melt 3.5 meters high from fire inside a building assuming residential or office fire load.

We don't have fire contractors here who can answer it.

So still the best guys to answer and deal with these are structural engineers.. who must understand structural integrity of metal roof.. who deal with the hard problem no one else in the world can understand.

Hence my only question for now is. How long can a 0.5mm metal roof like the following last in a fire before it bends enough for fire to escape or bend or warp?

Someone of you should know this. Isn't it.

Usually metal roof are not made of pure metal or iron but are roll formed made from hot-dip galvanized cold rolled mild steel.
Does this make it more fire resistant than normal a36 steel used in wide flange for example? So when the wide flange and purlins were already melting away and warping, somehow the 0.5mm thin metal roof is still stable (by some engineering marvel.. this is what the roof contractor is guessing)?

 

[hokie66]

It has essentially zero fire resistance.

 

[Pixy]

It has essentially zero fire resistance.

But how many minutes before it can melt? 5 minutes? 15 minutes? or you mean 0 minutes? Please give me ideas how long in minutes.

What temperature before a metal roof melt?

I couldn't see even one picture of melted metal roof in the entire internet. Thanks.

 

[hokie66]

The melting point is irrelevant in terms of fire rating. But the melting point of steel is about 1300 C.

 

[Pixy]

In a fire with typical office paper fire load. What is the temperature usually at the top of the metal roof. Can it reach 1300 C? If it only reaches half or 700 C? The metal roof can't melt?

For those material with rated 1 hour or 2 hour fire rating.. what is the temperature usually considered?