Page 300 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 6 APPLICATIONS OF BRIDGE DESIGN AND RATING METHODS 275

6. M 3 A f (d 6 a/2)
n
s
s
y
7. Minimum reinforcement required to develop M r
Lesser of 1.2 M or 1.33 M (LRFD 5.7.3.3.2)
u
cr
M 3 ) M Eq. (6-4)
r
n
1.2 M 3 1.2 (f 4 f ) S 6 M d,,nc (S / S 6 1) (LRFD 5.4.2.6)
cr
r
b
bc
pb
bc
S 3 I/ y t
bc
f 3 0 (no prestress)
pb
M d,,nc 3 0 (non-composite dead load moment)
8. Critical section for shear (LRFD 5.8.3.2)
Effective shear depth d 3 M / (A f f A ) (LRFD 5.8.2.9)
n
ps
v
s y 4 ps
Maximum of 0.9 d and 0.72 h LRFD Eq. (C5-9)
e
or distance between resultants of tensile and compressive forces.
Compute dead load shear V and V DW
DC
V 3 V 4 Vs
n
c
0.5
V 3 0.0316 b d (fc1)
c
v
v
Vs 3 d Cot 0 (A f )
v
s y
6.9.1 General Load Rating Equation (LRFD 6.4.2)
RF 3 [C 6 ( ) (DC) 6 ( ) (DW) ? (P)] / (LL 4 IM) (EQ 6-1)
DW
P
L
DC
1. Factors for inventory rating: 3 1.25; 3 1.25; 3 1.75
LI
DW
DC
Factors for operating rating: 3 1.25; 3 1.25; 3 1.35
LO
DW
DC
Operating rating 3 Inventory rating x ( / )
LI
LO
2. Design rating equation
Strength I limit state:
C 3 () ) () ) ()) R n
s
c
RF 3 [() ) () ) ()) R 6 ( ) (DC) 6 ( ) (DW)] / (LL 4 IM) (LRFD 6.5.4.1)
c
DC
DW
L
n
s
Condition factor () ) 3 1.0 for no deterioration. (LRFD 6.4.2.3)
c
System factor () ) 3 1.0 for a slab bridge. (LRFD 6.4.2.4)
s
Resistance factor ()) 3 0.9 for flexure (LRFD 5.5.4.2)

IM 3 1.33
3. Compute legal load rating
4. Compute permit load rating
Table 6.10 Rating summary table.
Design Live Load Rating Legal Load Rating Permit Load Rating
Limit State Inventory Operating T3 T3S2 T3-3
Strength I Flexure
Shear
Strength II Flexure
Shear
Service II
Fatigue