Hi,
Is there a way to allow Concept to check/ design Class C Prestressed Flexural members per ACI318-11 18.3.3.? We keep getting the 18.3.3 failure but the max allowable stress that is calculated limits the slab to Class T. I saw in another question on this forum that you can model tendons but uncheck the "Consider as PT" option. Is this how you would model Class C to eliminate the service stress limitations? And if that is the case, will Concept still perform all the other necessary PT calcs and checks on the design?
Thank you,
Per the ACI spec, all post-tensioned two-way slabs are considered as Class U with ft ≤ 6 root fc', but if you specify design strips that ate class C beams or one-way slabs you could get around that.
We do have our design strips set to one-way, and the max allowable capacity calculated by Concept is the 12 root f'c, so we aren't being limited to Class U.
Seth,
We figured out the issue. The PT classification is listed under the "Environment" setting for the design strip. We had initially thought the Class U, T, and C in the environment selection to be a coincidence with the naming of the PT classifications but not related because environment is not the only parameter used to determine which PT class to use in design. Also, there was no mention of Uncracked, Transitive, and Cracked in the Environment setting, just Corrosive, Normal?, and Protected.
We would recommend that this setting be changed to "PT classification" or "PT Assumed Behavior" to match the code nomenclature which may point users in a more appropriate direction than "Environment". I can only speak for the nomenclature in ACI, so I apologize if this aligns with AS or some other code.
Thank you again for your help, this forum has been a very useful resource.