×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Preliminary Area of Steel

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

Measure twice, cut once.

RE: Preliminary Area of Steel

I am not familiar with those estimating tools, but vaults typically need more reinforcement than required structurally, for security reasons.

RE: Preliminary Area of Steel

ronjon322:

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 smile ...no chance of the 'occupant' escaping!

RE: Preliminary Area of Steel

I assumed the vault was a utility vault (fairly common), not a bank vault or burial vault.
Sometimes, it's worthwhile just to ask the person that wrote the equation, tho.

RE: Preliminary Area of Steel

For ASD, As = (M x 12)/(fs x j x d) = M / (1.76d)
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.

www.PeirceEngineering.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources