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Re: Buliding steel frame's columns embedded in concrete

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I am by no means an expert in steel construction, however, what you discribe
is a typical moment connection where fixity is gained in the bottom of the
columns and transfered to a concrete grade beam. The steel that you discribe
are shear stirrups and would probably be spaced as close as 3" apart within
one foot of the column, then 6" apart for the next foot or so and finally 8
to 12" apart for the remainder of the length of the grade beam. There should
also be top and bottom horizontal steel runing through the grade beam that
either passes the column and is bent down or up at the back of the gradebeam
or is welded to the flange of the column. The moment reaction from the steel
is transfered to the gradebeam which can be designed as a typical concrete
beam with applied moments at the end AND which is considered as a beam on
elastic foundation for design with consideration of soil capacity.
Typically, the axial load is distributed below the column by means of a
spread footing which the column is attached to and which acts as an erection
pad prior to placing the grade beam. In most area's the grade beam is
designed with concrete exceeding f'c of 3000 psi and current UBC requires
special deputy inspection of the concrete to insure adequate placement of
all steel.
Sorry if this is too simplistic an explanation, but I'm not sure where you
are comming from on this. I use this type of detail often for the design of
laterally resisting frames in residential and unreinforced masonry
structures because you can reduce steel size by providing fixity at the base
rather than at the beam/column connection.

Dennis Wish PE

-----Original Message-----
From: K. Hemmatyar <kch(--nospam--at)ultranet.ca>
To: seaoc(--nospam--at)seaoc.org <seaoc(--nospam--at)seaoc.org>
Date: Tuesday, October 14, 1997 4:00 PM
Subject: Buliding steel frame's columns embedded in concrete


>Recently I've noticed a two storey commercial building under the
>construction here in our city, Vancouver (Canada.) The front steel moment
>resisting frame of the building has its columns embedded in the concrete
>foundation. I noticed that there are some stirrups around the columns in
the
>foundation.
>These types are common in gas stations. Does anyone have any comment on
this
>type of column to foundation connection in a Commercial Building?
>
>Casey Hemmatyar, P. Eng.
>
>
>
>