deflection

> We have a precast prestressed concrete slab unit. The precast slabs have a 6" minimum overlay. The slab unit camber diagram has
> A. Estimated camber due to prestress =6"
> B. Deflection due to dead load of precast prestressed slab unit =4 7/8"
> C. deflection due to dead load of parapet and deck overlay = 1"
> D. Net final camber = 1/2"
>
> Lets say at the center line of span final deck elevation is to be 100.00 Lets assume I shoot the center line of prestressed slab at 99.50 My question is do I add 1" plus 1/2" together to get .12 and therefore have a pre concrete placement elevation of 100.12 at the center of span making the fill 0.62' or would I just use the net final and just use .04 making pre pour elevation of 100.04 for a fill of 0.54

I will preface with, I think I have wrapped my brain around what you are describing

if FF elev wants to be 100.00', but the net final camber is 0.04' then your target elev for topping slab at the CL would be 100.04', and that b and c deflections balance one another. the engineer is probably allowing the 0.04' for future creep/settlement due to DL. we don't know unsupported spans, or beam spec's etc.

I have done a fair amount of camber work, but only in CIP reinforced concrete, nothing with prestessed, so I am using a mind's eye picture.

a sketch may help

🙂 Thank you for your response which the engineer confirmed to be correct just minutes ago.

When in doubt, stake to finish grade and clearly mark it on the stakes. [sarcasm]Refer all questions to the engineer and/or architect.[/sarcasm]