Hello,
My RAM Concept Model is showing a failure at slab midspans in the Design Status: Status Plan. However, when I audit the cross section the Final Check for ACI 318-14 Service Designer Section Analysis says No Failures.
For example, the attached screenshot shows the Audit of 24C-2, section 6 stating No Failures, but the Gross Bottom Stress max demand is 347.3psi while the max capacity is 158.5psi.
Where did the 158.5psi max capacity come from? The RAM failure in the Status Plan references ACI Sections 8.3.4.1/24.5.2.1. Per Table 24.5.2.1, our two-way PT slab should be analyzed as Class U with ft </= 6*SQRT(f'c). Our f'c = 6280psi, so the max capacity should be 475psi. We are analyzing an existing PT slab that was constructed in 2018. I've also uploaded the RAM Concept Model through the Secure File Upload for reference.
Thanks
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The RAM Concept file is titled "3RD Floor concrete slab model"
The capacity is based on 6 root f'c, 475 psi, but if the 2 root f'c limit of 158 psi is exceeded, then additional mild-reinforcement is required.
Okay, thank you for the response.
Our RAM Concept model has user defined bottom mild-reinforcement and bonded post-tensioned tendons. Since the Audit of 24C-2, section 6 states No Failures, does that mean we have sufficient bottom mild-reinforcement and bonded post-tensioned tendons? This is my interpretation of the last bullet point in your screenshot.
That sounds correct. In the model you sent me, there were failures in Span 24C-2, but those were top stress issues at the supports.
One correction: The existing building has unbonded tendons, not bonded tendons. Do we still have sufficient reinforcement after exceeding the 2*SQRT(f'c) capacity if the PT tendons are unbonded?