Thomas G. Marshall wrote:
RicodJour said something like:
On May 18, 8:45 pm, wrote:
On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting
wrote:
Thomas G. Marshall wrote:
said something like:
The concrete in steel lolly columns is to help keep them from
collapsing in a fire.
....so the preventing a dent thing is secondary, or not a
concern...?
No, preventing buckling is a significant advantage provided by
filling a steel column.
Uh, yes. And the buckling it prevents would be the result of fire.
Filling the columns with cement is to protect the columns from
buckling in a FIRE.
In a wood framed building? I guess if the fire started at the base of
the column that might be a good argument, but in any real situation
the house would be engulfed in flames long before the plastic
temperature of the steel was reached.

The concrete fill is to prevent buckling, partially from being dented,
but also to prevent localized failure which can occur at lower loads
than the straight compressive strength of the material(s) would
indicate.aconcern, though secondary,
only because the plasticity of steel could never be reached in a basement
without the rest of the house already having been reduced to dust. Or so it
seems to me. {shrug}

The problem with fire and steel beams/columns isn't so much from
structural weakness when the steel becomes hot, although that would be a
concern where the intention is to contain the fire for a length of time,
but more from the actual expansion of the steel, either from it pushing
other structural elements, or itself buckling when the expansion at both
ends is restricted.


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