Structural Concrete - Hassoun

22.9 Deflections (AASHTO 5.7.3.6) 927
The maximum moment due to DW: future wearing surface (AC overlay)
M DW = w DW_intx(L − x) (0.28)(50)(100 − 50)
= = 350 kip ⋅ ft
2
2
2. Live Load
Maximum moment due to uniform lane load of 0.64 klf:
(0.64 klf)x(L − x) (0.64)(50)(100 − 50)
M uniformLL = = = 800 kip ⋅ ft
2
2
Maximum moment due to design truck of HL-93 without dynamic load allowance
( ) ( )
9
M HL93 = 16 kip
8 L + 24.5ft2
9 24.5
− 17.5 ft = 16 (100) +
L
8 100 − 17.5
= 1523.9 kip⋅ ft
Maximum moment due to design tandem without dynamic load allowance
( ) ( L 3ft2 100
M Tandem = 50 kip − 1ft− = 50
4 L
4 − 1 − 3 )
− 1198.5 kip⋅ ft
100
M truck = Max(M HL93 , M Tandem )=max(1523.9, 1198.5) =1523.9 kip⋅ ft
Therefore, design truck will govern the maximum moment [combination (b) in Fig. 22.8].
Pedestrian Live Load (AASHTO 3.6.1.6)
Pedestrian load of 0.075 klf shall be applied to all sidewalks wider than 2.0 ft with vehicular live load
in vehicle lane.
If no side walk provided, therefore, no pedestrian live load is applied.
The maximum moment due to live load including the effects of dynamic load allowance and
load distribution factor is calculated below:
M LL = DM int {M uniformLL +[(1 + IM)M truck ]} = 0.845[800 +(1 + 0.33)1523.9] =2389.7 kip⋅ ft
FACTORED MOMENTS
Factored Moments
Load Factor Combinations:
Use for girder design-working stress
Strength I
Service I
Service III
1.25(DC) + 1.5 (DW) + 1.75(LL + IM)
1.0[DC + DW + (LL + IM)]; HL 93 only
1.0[DC + DW + 0.8(LL + IM)]; HL 93 only
Strenght I = 1.25(M DC1 + M DC )+1.5(M DW )+1.75(M LL )
= 1.25(2045.6 + 255.6)+1.5(350)+1.75(2389.7) =7583 kip ⋅ ft
Service I = 1.0(M DC1 + M DC2 + M DW + M LL )=1.0(2045.6 + 255.6 + 350 + 2389.7)
= 5041 kip ⋅ ft
Service III = 1.0(M DC1 + M DC2 + M DW + 0.8M LL )
= 1.0[2045.6 + 255.6 + 350 + 0.8(2389.7)] = 4563 kip ⋅ ft