From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
Date: Wed, 29 Mar 2000 17:20:49 -0500
ACI 318-56 specifies the minimum reinforcing as:
"Wherever at any section positive reinforcement is indicated by analysis, the
amount provided shall be not less than 0.005b'd except in slabs of uniform
thickness." b' is the width of the web in T and I flexural members, or the
width of rectangular flexural members.
IIRC, the major revision in ACI 318-56 from the previous edition was a change
in increasing the shear reinforcing requirements as a result of the
Wright-Patterson AFB hanger problems (caused by a "we know more than all
those old guys so we can make drastic changes in the Code and use less
Concrete strengths were typically 2,000 and 2,500 psi. fsubc was .45f'subc.
Allowable stresses in reinforcing were:
20,000 psi for intermediate and hard grade
18,000 psi for structural grade
Intermediate grade was the common grade, IIRC.
ACI 318-56 told you everything that you needed to know about concrete design
in 67 pages (5 X 9, not 8.5 X 11).
Hope this helps.
A. Roger Turk, P.E.(Structural)
Ron Martin wrote:
>>I have a project with an older building (built in 50s I think) that has
some of the concrete spalling off . The building is a concrete beam/column
system with about 6" concrete walls and concrete roof. To date, all I see is
the clear cover spalling off the main beams and some roof purlins/joists. I
do not see any major damage to the section other than this spalling. It is
spalling back to the tension reinforcing/stirrups.
Any good suggestions for providing protection of the steel?. The inside of
the building has fairly high humidity. Water is used in their process.
Also, does anyone have an idea what was "considered" minimum reinforcing back
in the 50s. We do not know what reinforcing was used during the original
construction. I was wanting to estimate the beam strength based on current