Page 255 - Bridge and Highway Structure Rehabilitation and Repair

230 SECTION 2 STRENGTHENING AND REPAIR WORK

5.9.6 Plastic Distributed Live Load Moments and Shear
M 3 mgr [(M or M ) (1 4 IM/100) 4 M ]
Tr Ta Ln
Tr 6 Truck load
Ta 6 Tandem load
LN 6 Lane load
1. Distribution factors for shear: (4.6.2.2.3)
Cross section type (e) (Table 4.6.2.2.1-1)
• Interior beams (4.6.2.2.3a and Table 4.6.2.2.3a-1)
• Exterior beams (4.6.2.2.3b and Table 4.6.2.2.3b-1)
• Skewed bridges (4.6.2.2.3c and Table 4.6.2.2.3c-1)
• Distributed live load shears
V 3 mgr [(V or V ) 1.33 4 V ]
LL+IM Tr Ta Ln
2. Reactions to substructure: (3.6.1.3.1)
Reactions are per design lane without any distribution factors. The lanes shall be positioned
transversely to produce extreme force effects.
R 3 V 3 1.33 V 4 V
sup sup Tr LN
Calculate force effects from other loads.

5.9.7 Investigate Strength Limit State
1. U 3 [1.25DC 4 1.25DC2 4 1.5DW 4 1.75 (mgr) LL (1 4 IM)]
• Flexure
M 3 $ M 3 0.95 (1.25 M 4 1.50 M 4 1.75 M LL+IM )
DC
i
DW
i
Check 7 M 9 M
n u
Check #3 A / A 9# min
g
s
• Analysis
Main reinforcement perpendicular to traffi c
• Deck thickness for defl ection control
h min 3 (s 4 3000) / 30 : 175 (Table A2.5.2.6.3-1)
2. Dead loads:
• beams
2
2
M max 3 4 wL / 12 and 6 wL / 8
• 4 beams
2
M max 3 4 wL / 10 and 6 wL / 10
2
• 5 or more beams
• Use influence lines at 0.4 L of fi rst span

M 3 0.0744 wL 2
2
• Adjust for overhang moment 6 w l / 2
2
2
nd
2 span M 3 4 0.0471 wL and 6 0.1141 wL plot B.M. and S.F. diagrams.
3. Live loads:
Overhang 1140 4 0.833 X
• IM 3 33 percent of LL ( 3.6.2.1)
• Number of lanes
N 3 Int (Roadway width / 3600) (3.6.1.1.1)
• Multiple presence factor