Page 256 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 5 LOAD AND RESISTANCE FACTOR RATING AND REDESIGN 231

M 3 1.2 for one loaded lane
3 1.0 two
3 0.85 three
• Tire contact area
Wheel load is applied as a distributed load. For design live load both HL-93 and state
permit HL-93 single span loads are applicable (for truck and lane live load moments see
Chapter 4, Sections 4.11 and 4.12. Tables 4.5 and 4.6 refer to Section 5.8 for strength and
serviceability conditions). For continuous beam positive moments Tables 4.5 and 4.6 may
be used for preliminary design and checked by a continuous beam analysis software.
5. Design:
M 3 7M 3 A f ( d 6 a /2)
s
y
n
u
a 3 A f / 0.85 f 1 b
y
s
c
A 3 (M / 7 ) / f jd
u
y
s
6. Check ductility: a 0.35 d
Minimum reinforcement # 0.03 f 1 / f ( 5.7.3.3.2)
c
y
Maximum spacing smax 3 450 mm or 1.5 h (5.10.3.2)
Distribution reinforcement 3 3840/ S % (9.7.3.2)
e
where S is the effective span length. (9.7.2.3)
e
Shrinkage and temperature reinforcement:
Temp A 0.75 A / f (5.10.8.2)
s
y
g
Crack control: f Z / (d A) 0.33 0.6 f (5.7.3.4)
c
y
s
Z 3 23000 N/mm
d 50 mm

5.9.8 Calculate Deflection and Camber (Table 3.4.1-1)
Service I limit state 3 1, gravity load factors 3 1
• U 3 DC 4 DCE 4 DW 4 LL 4 IM
• LL defl ection criteria
• Distribution factor for defl ection.
allow 3 Span / 1000 for bridge with sidewalks
Section properties E 3 4800 f 1, f 3 0.63 f 1
r
c
c
c
Calculate I g,
Calculate I e
M 3 f I / y t
cr
g
r

Calculate live load deflection at location where moment is maximum.
3
3
I 3 (M / M ) I 4 [1 6 (M / M ) ] I I g
cr
cr
a
a
g
e
cr
Dead load camber w DL 3 w DC 4 w DC2 4 w DW
Perform unit load analysis and calculate defl ections.
5.9.9 Investigate Fatigue for Steel
Fatigue limit state (Table 3.4.1-1)
U 3 0.75 (LL 4 IM)
f
• Determine need to consider fatigue