Steel Bridge Decks Factors Affecting Casting Sequence Dennis Golabek, P.E.

Steel Bridge Decks
Factors Affecting Casting Sequence
Dennis Golabek, P.E.
Assistant State Structures Design
Engineer
AGENDA - Steel Bridge Decks
Factors Affecting Casting Sequence

FDOT Survey

Factors

Design Criteria

Design Example
FDOT SURVEY

Constructed between
2000-2013
11 / 7
2/1

2-Span Continuous
Steel
25 / 5
3/2

9/6
67 Bridges
 30 - No cracks
10 / 5
 12 - Cracks in Pour 1
 27 – collect data
- 13 no cracks
- 14 with cracks
7/1
FDOT SURVEY

Design Code

L1/L2 or L/D Ratio

Concrete Strength

Deck Placement

Placement
Termination

Reinforcement
L1
L2
LPLC1
PLC 1
LPLC2
PLC 3
PLC 2
FDOT Survey

General Observations
 Deck Placement
Sequence
70% L1
PLC 1
70%L2
PLC 3
PLC 2
 Deck termination
L1
L2
 Span/Span ratio
AVG L1/L2 = 1.05 for uncracked
 Reinforcing
Termination
AVG L1/L2 = 1.12 for cracked
FACTORS

Shrinkage and Temperature
 Spec 400-7.1 cold and hot weather
 Spec 400-16.1 Surface Moisture
 Spec 400-16.4 curing for bridge decks

Wind velocity – Section 400-7.1.3

Temperature difference during the day

Contractor changes deck placement sequence

Designers do not properly consider the deck
placement sequence in design
CRITERIA

AASHTO LRFD BDS

FDOT Structures
Manual
Criteria - Longitudinal tension stresses in
the concrete deck

AASHTO LRFD BDS
 6.10.1.7 – Load Combination Service II
1.0 DL + 1.3 (LL+IM)
 6.10.3.2.4 – Factored Construction Loads
Criteria - Detailing

AASHTO LRFD BDS
 1% Steel – 2/3 in top layer
Criteria - longitudinal tension stresses in
the concrete deck

FDOT Structures Design Guidelines
 4.2.7 Minimum Negative Flexure Slab
Reinforcement [6.10.1.7]
- Any combination of DL and LL is considered
 4.2.8 Crack Control in Continuous Decks [5.10.8]
-
Deck Casting Sequence
Limit Pours
Camber Diagrams
Concrete Strengths
Longitudinal Tension Stresses per LRFD [6.10.3.2.4]
 4.2.9 Concrete Decks on Continuous Steel Girders
- Longitudinal reinforcing steel per LRFD [6.10.1.7]
Criteria

Deck Casting Sequence

Limit Pours

Concrete Strengths

Camber Diagrams
200 to 400 cy
Criteria

FDOT Structures Design
Guidelines/Detailing
Manual
 2.13.1 Constructability
Limit State Checks (Rev
01/14)
EXAMPLE – Calculate longitudinal tension
stresses in the concrete deck

Bridge Configuration

Deck Placement and
Live Load Analyses

Deck Stresses

Check for Uplift
EXAMPLE

Bridge Information
 Span length
N = 1.23
 Typical Section
Leff/D = 26
 Girder Elevation
EXAMPLE

Deck X-sect Area
Deck Placement
End Bent
Width=
55.083 ft
Thickness=
9 in
PLC 1
PLC 3
PLC 2
L (ft)
90
70
130
Vol (cy)
138
107
199
End Bent
Pier
90 ft ~ 70%
PLC 1
130 ft
40 ft
30 ft
PLC 3
130 ft ~ 80%
PLC 2
160 ft
EXAMPLE

Section Properties
 SDG Table
 2nd Placement – 1st
placement 3 days old
EXAMPLE

Deck Placement and Live Load Analyses
End Bent
Pier
End Bent
90 ft
PLC 1
130 ft
3 days
PLC 2
EXAMPLE

Deck Placement Analyses
Pier
End Bent
6 days

PLC 3
Live Load Analysis
End Bent
28 days
End Bent
70 ft
Pier
3 days
End Bent
EXAMPLE

Uplift
Steel
9k
86k
25 k
PLC 1
71 k
64k
9k
EXAMPLE

σconc =
σsteel/n
Longitudinal tension stresses in deck
Dist.(ft)
0.0
7.8
15.5
23.3
31.0
31.0
45.8
60.5
75.3
90.0
90.0
92.8
95.5
98.3
101.0
Steel Only
PLC 1
PLC 2
Construction
Strength I
PLC 3
M (k-ft)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
M (k-ft)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
M (k-ft)
0
-166
-331
-497
-662
-662
-978
-1293
-1608
-1923
0
0
0
0
0
Deck σ (ksi)
0.000
-0.046
-0.092
-0.139
-0.185
-0.161
-0.238
-0.314
-0.391
-0.468
0.000
0.000
0.000
0.000
0.000
M (k-ft)
0
25
50
75
100
100
147
194
242
289
0
0
0
0
0
φfr = 0.358 ksi
LL+I
Service III
Moment (k-ft) Deck σ (ksi)
0
0.000
-124
-0.070
-247
-0.140
-371
-0.210
-495
-0.280
-495
-0.243
-730
-0.359
58’
-965
-0.475
-1201
-0.591
-1436
-0.707
-1436
-0.390
-1480
-0.402
-1524
-0.414
-1568
-0.426
-1612
-0.438
φfr = 0.458 ksi
EXAMPLE

Reinforcing Detailing
 SDG 4.2.11 Temp & Shrinkage – No. 4 (min) at
12-inch (max)
 LRFD BDS – No. 6 max, 12-inch max and 1%
Steel – 2/3 in top layer
Spa
Deck X-sect Area
size
area
no
in2
Width=
55.083 ft
Thickness=
9 in
Top
Bot
sacrificial=
0 in
area =
5949 in2
1 % steel =
59.5 in2
Total
in2
12
5
0.31
55
17.1
12
6
0.44
51
22.4
6
4
0.2
92
18.4
4
0.2
8
1.6
59.5
total steel % =
1.00%
top steel % =
0.66%
EXAMPLE - Reinforcing Detailing
EXAMPLE

Reinforcing Detailing
 Negative moment regions
End Bent
Pier
90 ft
40 ft
72 ft
Inspection reveals
extensive lateral
cracking near end
of Pour 1
30 ft
PLC 3
PLC 1
End Bent
Plans
130 ft
PLC 2
Example

Other Ways
 Change placement limits
 Change sequence
Deck X-sect Area
Example

Other Ways
 Change limits (50%L)
-
Width=
55.083 ft
Thickness=
9 in
PLC 1
PLC 3
PLC 2
L (ft)
65
145
80
Vol (cy)
100
222
122
Placement quantity
Deck longitudinal tension stress
Uplift
Reinforcement termination
End Bent
End Bent
Pier
65 ft
65 ft
80 ft
80 ft
PLC 2
PLC 3
PLC 1
130 ft
160 ft
Example

Change limits (50%L)
End Bent
65 ft
65 ft
80 ft
80 ft
PLC 2
PLC 3
PLC 1
Dist.(ft)
0.0
7.8
15.5
23.3
31.0
31.0
39.5
48.0
56.5
65.0
90.0
End Bent
Pier
Steel Only
PLC 1
PLC 2
Construction
Strength I
PLC 3
M (k-ft)
0
0
0
0
0
0
0
0
0
0
0
M (k-ft)
0
0
0
0
0
0
0
0
0
0
0
M (k-ft)
0
-76
-151
-227
-302
-302
-385
-468
-551
-633
-1923
Deck σ (ksi)
0.000
-0.021
-0.042
-0.063
-0.084
-0.073
-0.094
-0.114
-0.134
-0.154
-0.468
M (k-ft)
0
38
76
114
151
151
193
234
276
317
289
φfr = 0.358 ksi
LL+I
Service III
Moment (k-ft) Deck σ (ksi)
0
0.000
-124
-0.047
-247
-0.094
-371
-0.141
-495
-0.187
-495
-0.163
-630
-0.208
-766
-0.253
-902
-0.297
-1037
-0.342
-1436
-0.707
φfr = 0.458 ksi
Deck X-sect Area
Example

Change sequence
 Placement quantity
Width=
55.083 ft
Thickness=
9 in
PLC 1
PLC 3
PLC 1
L (ft)
78
148
64
Vol (cy)
120
226
98
 Uplift
 Deck longitudinal tension Stress
 Reinforcement termination
End Bent
78ft (60%L1)
PLC 2
130 ft
End Bent
Pier
52 ft
96 ft
64ft (40%L2)
PLC 3
PLC 1
160 ft
EXAMPLE

Uplift
Steel
9k
86k
25 k
6k
30k
67 k
PLC 1
Example
 Change
End Bent
placement limits
End Bent
Pier
78ft (60%L1)
52 ft
96 ft
64ft (40%L2)
PLC 3
PLC 2
PLC 1
Steel Only
PLC 1
PLC 2
Construction
Strength I
PLC 3
Dist.(ft)
M (k-ft)
M (k-ft)
M (k-ft)
Deck σ (ksi)
M (k-ft)
96
100
104
107
111
111
123
136
148
160
SPAN 1 90.0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-503
-474
-445
-416
-387
-387
-290
-193
-97
0
-1923
-0.110
-0.104
-0.097
-0.091
-0.085
-0.091
-0.068
-0.045
-0.023
0
-0.468
1612
1519
1425
1332
1239
1239
929
619
310
0
289
φfr = 0.358 ksi
LL+I
Service II
Moment (k-ft) Deck σ (ksi)
-701
-661
-620
-580
-539
-539
-404
-270
-135
0
-1436
0.021
0.019
0.018
0.017
0.016
0.002
0.001
0.001
0.000
0.000
-0.707
φfr = 0.458 ksi
Example
 Change
End Bent
placement limits
End Bent
Pier
78ft (60%L1)
52 ft
96 ft
64ft (40%L2)
PLC 3
PLC 2
PLC 1
Steel Only
PLC 1
PLC 2
PLC 3
Construction
Strength I
Dist.(ft)
M (k-ft)
M (k-ft)
M (k-ft)
M (k-ft)
Deck σ (ksi)
0
8
16
23
31
31
43
55
66
78
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-36
-71
-107
-142
-142
-196
-250
-304
-358
0.000
-0.011
-0.021
-0.032
-0.043
-0.037
-0.051
-0.066
-0.080
-0.094
φfr = 0.358 ksi
LL+I
Service II
Moment (k-ft) Deck σ (ksi)
0
-124
-247
-371
-495
-495
-682
-870
-1057
-1245
0.000
-0.030
-0.059
-0.089
-0.119
-0.103
-0.143
-0.182
-0.221
-0.260
φfr = 0.458 ksi
SDG 4.2.8 – 2015 Revisions