Design of a T-beam - Reinforced Concrete with FRP Bars: Mechanics and Design - page 293

Deflection at midspan [2]: C alculate the moment at midspan due to ser-
vice load on a simply supported beam, M o :
M o = 405.4·ft·kip
The maximum deflection under service loads is ξ = 2 and λ = 1.2.
Maximum deflection under service loads is

2 2

5M 1
48E

⋅ ⋅

⋅

1
16E

( )

o1 1

∆ : = − M+M ⋅ =0.367 in. ⋅

SL s1 s3

I ⋅ I

ce ce

Deflection due to dead loads only is

w
w

D

∆ : = ∆⋅ =0.235 in. ⋅ DL SL

SPos

Deflection due to live loads only is

w
w

LPos

∆ : = ∆⋅ =0.132 in. ⋅

LL SL

SPos

Long-term deflection is

Δ LT := Δ LL + λ·(Δ DL + 0.20·Δ LL ) = 0.446·in.

“OK” if
“Not good”otherwise

≤∆ ≤∆

LT lim

Check_: ∆

=

LT

Check_Δ LT = “OK”
Midspan deflection diagram [2] and ACI 440.1R-06:

0

0.3

0.7

1

0 6 24 30

12 18

Beam B1, ft

Bischoff's long term deflections
Dead load deflections
Live load deflections
ACI 440 long term deflections
Deflection limit