Long term deflection 1

[happayday]

what is the long term deflection limitation for the two way concrete slab? ACI 9.5.2.5(ACI 318-99) EQ 9-10 is too confusing, is any quick way to get the allowable deflection limitation to compare the result we got from ram concept?

 

[Galambos]

see Table 9.5(b) under "Deflection to be Considered"

Ted

 

[AUCE98]

Happyday,

Your long-term amplification factor per ACI 9.5.2.5 is (2) for accounting for creep and shrinkage in slabs. However, a multiplier of 2 is typically not adequate to estimate deflections in conventionally reinforced two-way slabs. Several studies have indicated that a value of 3-4 should be used to estimate long term losses, or a lower modulus of rupture strength of 4*f'c^1/2 to account for cracking due to shrinkage restraint at columns. I would suggest the paper "Long Term Multipliers for Estimating Two-Way Slab Deflections" by Graham and Scanlon, ACI Journal Nov-Dec 1986. It has some good information that may help you determine the multiplier to use in Concept. In addition, ACI 435R Control of Deflections in Concrete Structures has information regarding the same topic.

Good Luck,

AUCE98