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Re: Bridge Questions

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The 1957 AASHO Bridge Specs is as far back as I go.  Concrete
classes are defined there (2.4.5) according to their intended

"Class A or Class (AE) concrete shall be used for all
superstructures, except as noted below, and for reinforced
substructrures except where the sections are massive and lightly
reinforced.  The more important items of work included are slabs,
beams, girders, columns, arch ribs .... ."

The table in 2.4.4 gives the approximate mix proportions for the
various classes of concrete.  Section 1.4.11(b) states that
minimum compressive stress for Class A or A(AE) is 3,000 psi,
although in the 1940's it might have been less, say 2,500 psi. 
(Use .4f'c for allowable stress, WSD.)

A15 reinforcing is sub-classified as Structural, Intermediate,
and Hard Grade with yields of 33, 40 and 50 ksi, respectively. 
(Working stress levels: [Section 1.4.12] Tension in flexural
members and tension in web reinforcing: 15 ksi for Structural
Grade, 20 ksi for Intermediate and Hard;  compression:  13.2 ksi
for Structural Grade, 16 ksi for Intermediate and Hard.  Bond
[all grades]:  exclusive of top bars: .1f'c [max 350 psi];  In
2-way ftgs: .08f'c [max 280 psi]; Top bars: .06f'c [max 210])

Your local university library may have AASHO specs from the
1940's or call AASHTO (1-888-227-4860).

Pull the timber piles!  It should not be hard using a vibratory

Hope this helps.

A. Roger Turk, P.E.(Structrual)
Tucson, Arizona