×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Composite column:Fire resistance

Composite column:Fire resistance

Composite column:Fire resistance

(OP)
Let us say i have a composite column section consisting of structural steel, concrete and reinforcing steel.
Under fire, as per eurocode, we need to divide the column section into various layers and get the temperature in every layer.

What is the reason that the temmperature in every layer varies so largely?Can anyone explain with a intuitive/physical reasoning??

Plz help!!

RE: Composite column:Fire resistance

I am not familiar with the Eurocodes but Chapter 7 of the International Building Code adopted almost entirely across the United States, allows you to "build" an equivalent rating by adding up the prescriptive fire-resistance values of each material as you build your section.  If you have a Type I or IIA building, and you need a 2 hour rating on your columns, you can use, perhaps, a combination of drywall and masonry to create that rating to protect the steel - or a combination of drywall and concrete encasement of the steel.

Don Phillips
http://worthingtonengineering.com

RE: Composite column:Fire resistance

cecil123,

The fire rating is based on the member heating up over a certain period of time. The outer layers heat up faster than the inner layers therefore creating a temperature gradient between the out side surface and the core.

csd

RE: Composite column:Fire resistance

(OP)
Is it anyways related to the difference in thermal conductivity between steel and concrete?Because steel has very high thermal conductivity and concrete comparatively low?

RE: Composite column:Fire resistance

That is on factor.

The concrete effectively acts as an insulator meaning that the steel closer to the surface heats up faster than that further from the surface.

The concrete will also have a varying temp across the section

RE: Composite column:Fire resistance

The properties of the layers of materials on a steel structural material provide reduced temperatures.

Temperature is a factor when it comes to buckling or other rapid failures. - A critical factor if you are considering life safety.

A parallel example is factors used by some insurance companies when quoting rates for interior contents. - A building with a wood truss may have a lower rate than a building with a steel truss because of a the unpredictable collapse. A wood structure loses strength according to loss of material (more or less), so the strength can be estimated (if it isn't burned much it is reasonsbly good), while you cannot determine the steel temperature, so fire fighters must "error" on the side of their life safety and evacuate. - More fire fighting time means less loss.

An explantion from an insurance company.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources