RC Two-way Slab Long-term Deflection

Hi all,

I'm studying a two-way RC flat slab for a parking garage. 10" thick, 6000psi concrete, 10psf SDL and 40psf LL. The 5000-day deflection is 3" under 1.0SW+1.0SDL+0.25LL for a 30'X27' interior bay.

With the same geometry and concrete strength, SAFE gives 1.5" under the same load combo with nonlinear cracked long-term properties - a creep factor of 2 and shrinkage strain of 0.0005.

Why does RAMConcept give a much higher long-term deflection?

Note:

• Concept creep factor is 3.35
• Concept shrinkage strain is 0.0004
• shrinkage restraint is 10%

Is it true that one needs to calibrate those factors to give a more reasonable long-term deflection for RC slab?

Thanks,

Jonathan