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ADAPT PT - Reinforcement questions...

ADAPT PT - Reinforcement questions...

ADAPT PT - Reinforcement questions...

(OP)
I have an 8" deep slab-on-grade that has 6 spans of varying lengths.  I am modeling a 12" strip in ADAPT PT.

Question1) What exactly does the 'Live Load Factor' value affect?  Does the program arrange live loads per the ACI-05 (as I selected through the wizard)? Per ACI 8.9.2, the live load arrangement should either be on two adjacent spans or on every other span.  Is this what the program is performing?

Question 2) It appears that the program is requiring additional mild reinforcement on the top of the slab at midspans even though all my service stresses are WITHIN code limits.  I would not expect this since additional rebar would be required ONLY if my service stresses exceed code limits.  Am I missing something?

Question 3) The program is calculating minimum steel for the slab to be 0.004 times the area between the CG of the slab and the top or bottom fibers for both TOP and BOT rebar throughout all the spans.  I would expect this code-minimum steel to be required only at a)the bottom of the slab at midspan and b) at  top of slab at the supports.  In other words, minimum mild reinforcement would be placed where we would expect tension to be as if it were a regular RC slab, not on both the top and bottom of the slab at all locations.

Thank you in advance for your answers.
 

RE: ADAPT PT - Reinforcement questions...

Concerning question 1 The "Live Load Factor" is what percentage of LL do you want for pattern loading. This comes from ACI 318 13.7.6 which only requires 75% in pattern loading

Is this a PT-Slab on grade or a mild reinforced slab? ADAPT-PT is only used for structural slabs.

ADAPT-PT will use the requirements for ACI 318 Chapter 18. So steel maybe showing up because of that. ADAPT may be set to the two-way setting as well which will change your minimums.

The 0.004 minimum is for any non two-way slab member. With pattern loading you may be getting a negative moment across whole spans if you live load is very high compared with your dead load. Check ACI 318 18.9 for information regarding minimums.  

RE: ADAPT PT - Reinforcement questions...

Also the required reinf isn't because of the stress check analysis but is from the ultimate strength check.

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