Can anyone help me understand an apparent conflict in the program help docs ? I'm trying to determine how much Longitudinal steel to supply in the cap check a Pier Cap Design for Torsion, and one section seems to contradict the next section.
Under Theory> Design> Cap Shear and Torsion Design (AASHTO LRFD): The Program Help manual says that the "program reports the additional required effective steel (Alx). This already accounts for excess effective steel present at that section, which is more than the required flexural.
AND
Under Theory> Design> Cap Shear and Torsion Design (AASHTO Standard Load Factored), the Program Help manual says that "For AASHTO Standard, the program reports the total longitudinal steel required for torsion (Alt). Users may reduce this amount by provided steel in excess of required steel already present at that section."
Okay, what am I missing? The first section appears to say that you have to add longitudinal steel to your cap in the amount of Alx steel -- regardless of the difference between req'd and provided/effective flexural steel; the Second section appears to say that you can subtract the extra steel available (Aseff Asreq)- from the Alx value listed in the output.
Or does it depend on the Design Code you choose ?
Any help is appreciated.
Tom
Alx is the effective longitudinal steel required in addition to the provided effective flexural Steel.
Alx should be added to the Top reinforcement and in the negative moment region (Tension side) we leave it to the user’s judgment if they want to add that additional steel (Alx) so that code provision are followed as per article 5.8.3.5.And also you can see in the output we are not adding Alx to any of the longitudinal reinforcement but only thing we are doing is just reporting it so that its ultimately its left to the user’s judgment.
The torsional factor is included in the calculation of Alx as per 5.7.3.6.3-1 equation.Please check Tutorial 2 example where the 5.7.3.6.3-1 equation is used to calculate Alx value.
Thanks Vinay for the response and tutorial example. However, you didn't address the differences in the User Manual instructions.
Alt is the total longitudinal steel required due to torsion in addition to the REQUIRED flexural steel. as per AASHTO Standard.
The way I read this in both the codes Alt an Alx are additional steel and as I have mentioned in my previous reply that in the output we are not adding Alx to any of the longitudinal reinforcement but only thing we are doing is just reporting it so that its ultimately its left to the user’s judgment to add it or subtract it.
Also it depend on the Design Code the user chooses.
Please let me know if you need any additional information.