Hello,
I am working on designing an isolated footing pile cap using AASHTO LRFD 7th Ed. with 2016 interims. I have a successful flexural reinforcement design in a file created using version 19.02.00.33 of Leap Bridge Concrete where the Effective Steel Area is reported as almost equal to the Provided Steel Area. I believe the Effective Steel Area should be reduced due to the available development length being less than the required development length of the reinforcement. Can someone clarify how the Effective Steel Area is calculated in LBC as I am having difficulty finding an answer in the manual?
My calculations are:
Thank you,
Bradley Gersh
The Area is reduced linearly.
For example : At the end of development length(ld), rebar is fully developed and so 100% Ast-provided is available.At a location X' from the end of rebar, which is < development length, Aeff will be ( X * Rebar area / ld).
The Development length is designed based on AASHTO article 5.11.2 and the AsT/b eff is calculated as follows.
Example: At any location, if development length is 4' and location is 1'
The Ast/b eff=Ast_provided* (1’ or 2’) /4.
Ast_eff = Ast prov *( min (L/ld , 1) )
Ast-eff : Effective top steel area, after considering development length
If As-t eff is < than As-t req you will get a flag
Area Provided may be larger than required but at the same time the effective may be less than required within development length.
By providing additional rebar or increasing the length of the footing in that particular direction or trying to hook the bar will help .
I hope it helps