Page 254 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 5 LOAD AND RESISTANCE FACTOR RATING AND REDESIGN 229

• Longitudinal skin reinforcement required if web depth 9 900 mm (5.7.3.4)
• Shrinkage and temperature reinforcement
A 0.75 A / f (5.10.8.2)
y
g
s
6. Effective flange widths: (4.6.2.6.1)

• Effective span length 3 distance between points of permanent load infl exions
• Interior beams b ¼ effective span
i
12 t 4 b w
s
Average spacing of adjacent beams
1
• Exterior beams b ½ b ⁄8 effective span
e
i
6 t 4 ½ b w
s
width of overhang.
7. Non-composite and composite section properties
5.9.3 Resistance Factors
1. Select resistance factors: Table 7.10 (5.5.4.2)
2. Select load modifi ers: (1.3.2.1)
3 (0.95 1.0 1.0)
i
R
I
D
3. Select applicable load combinations: (Table 3.4.1-1)
• Strength I limit state
U 3 [1.25 DC 4 1.5 DW 4 1.75 (LL 4 IM) 4 1.0 (WA 4 FR)]
i
• Service I limit state
U 3 1.0 (DC 4 DW) 4 1.0 (LL 4 IM) 4 1.0 WA 4 0.3 (WS 4 WL)
• Fatigue limit state U 3 0.75 (LL 4 IM)
4. Calculate live load force effects:
• Select number of lanes (3.6.1.1.1)
• Select multiple presence factors (3.6.1.1.2)
5. Dynamic load allowance—IM (3.6.2.1)

5.9.4 Live Load Force Effects
1. Distribution factors for moment (4.6.2.2.2)
2. Cross section type (Table 4.6.2.2.1-1)
3. Interior beams with concrete decks (4.6.2.2.2b) and (Table 4.6.2.2.2b-1)
4. Exterior beams (4.6.2.2.2d) and (Table 4.6.2.2.2d-1)
5. Skewed bridges (4.6.2.2.2e) Reduction of live load distribution factors for moment in lon-
gitudinal beam are permitted.
skew 3 1 6 c (tan =) 1.5
1
3 0.25
0.5
c 3 0.25 (K / Lt ) (S/L) (Table 4.6.2.2.2e-1)
1
g
s
5.9.5 Load Combination Dead Load Moments and Shears
1. Dead loads for interior girders 6 DC, DW:
• Calculate interior girder unfactored moments and shears
• Dead loads for exterior girders 6 DC, DW
• Calculate exterior girder unfactored moments and shears.
2. Investigate service limit state:
• Investigate durability (C.5.12.1)
• Crack control (5.7.3.4).