Preliminary Area of Steel
Preliminary Area of Steel
(OP)
I'm reviewing a set of calcs for a precast vault in which the designer is using the shortcut formula to calculate the area of steel required in the walls. However instead of using the typical As=Mu/4d with factored loads he is using As=Mu/1.76d with unfactored loads. Where is the 1.76 coming from? Has anyone seen this before and can shed some light on it for me? I'm assuming it's from an older ASD or even WSD method.
Appreciate ya
Appreciate ya
Measure twice, cut once.






RE: Preliminary Area of Steel
RE: Preliminary Area of Steel
Not sure about 1.76. Seems very close to old masonry flexural design: As ≅ Ms/1.8d ...where Ms is a service-level (allowable/working) moment.
hokie66:
Maybe the vault is a burial vault...all DEAD load
RE: Preliminary Area of Steel
Sometimes, it's worthwhile just to ask the person that wrote the equation, tho.
RE: Preliminary Area of Steel
M = ft-kips (with unfactored service loads)
fs = 24 ksi (allowable tension)
j ~ 0.88 for f'c ~ 3250 to 4000 psi
d = dimension from compressive face of concrete to center of tension steel.
Reference: Foundation Analysis and Design, Joseph E. Bowles, 1968, McGraw-Hill, page 160.
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