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NCHRP 12-78
VOBUG Nashville– 2010
NCHRP 12-78Evaluation of Load Rating by LRFR
Mark Mlynarski, P.E. – Michael Baker Jr., Inc.Wagdy Wassef, Ph.D. P.E.- Modjeski and Masters, Inc.
Andy Nowak, Ph.D., University of Nebraska
1
NCHRP 12-78
AASHTO Bridge – T-18Update of NCHRP 12-78
Evaluation of Load Rating by LRFRPanel Members
Matt Farrar, Idaho – ChairTim Armbrecht, Illinois
George Christian, New YorkGeorge Conner, Alabama
Becky Curtis, MichiganWilliam R. Cox, ASBI
2
Artur D’Andrea, LouisiannaMurugesu Vinayagamoorthy,
CaliforniaDr. Pe-Shen Yang, ArizonaDr. Firas Ibrahim, FHWA
Waseem Dekelbab, NCHRP
NCHRP 12-78
Background
What is NCHRP 12-78?
3
NCHRP 12-78
Background
4
• NCHRP 12-46• “Guide Manual for Condition Evaluation and
LRFR of Highway Bridges, 1st Edition and 2005 Interim”
• HSCOBS wanted additional research to explain differences with LFR
• NCHRP 20-7 (Task 122) (Mertz)• Flexural ratings/ small sample
• NCHRP 12-78 -Evaluation of Load Rating by LRFR
NCHRP 12-78
12-78 Objectives
5
• Recommend refinements to the LRFR methods in the AASHTO MBE
• Explain changes in truck weight restrictions
• Develop a comprehensive database (1500 bridges) – Virtis Database
• Develop the proposed refinements
NCHRP 12-78
Topics
•Preliminary Phase
•Vehicle/Bridge selection
•Gathering/Analyzing
Importance of Virtis
NCHRP 12-78
Preliminary Phase
• Survey• Collect Virtis Data• Review/ Analyze NBI data
7
NCHRP 12-78
Preliminary PhaseSurvey
8
• Surveys sent to all states• Questions related to load
rating procedures• Solicit vehicle information and
bridge data (Virtis)
NCHRP 12-78
Preliminary PhaseSurvey
9
• Responses to survey (33 total) Manitoba
NCHRP 12-78
Preliminary PhaseCollect Virtis Data
10
AASHTOWare Bridge Data Manitoba
State#
Bridges
Alabama 3139Illinois 3232Michigan 378Missouri 4644New York 5412Oklahoma 44S. Dakota 1135Tennessee 53
Total 18038
NCHRP 12-78
Preliminary PhaseCollect Virtis Data
11
Other sources Manitoba State Bridges
Virginia 20 LRFRIdaho 100+
Auburn 100 BridgesOregon BRASS
500 LRFRNew York AdditionalWyoming 20-7 Task 122
Bridges
NCHRP 12-78
Preliminary PhaseCollect Virtis Data
12
• 18,000 + Virtis bridges• 1500 from these
• 300 + vehicles• 8 selected
NCHRP 12-78
Preliminary PhaseAnalyze NBI Data
13
• 2008 NBI data used• Software to analyze NBI DB• Certain records ignored
NCHRP 12-78
Preliminary PhaseAnalyze NBI Data
14
NBI Records IgnoredNBI Item Restriction/Items Ignored
5a – Record Type Ignore values <> 1
31 – Design Load 7- Pedestrian, 8-Railroad
41 – Structure Open/Posted/Closed
D – Open, would be posted or closed except for temporary shoring, E – Open, temp structure, K – Closed
43A – Kind of Material and/or Design
0 – other, 8- Masonry, 9-Aluminum, Wrought Iron, Cast Iron
NCHRP 12-78
Preliminary PhaseAnalyze NBI Data
15
NBI Records IgnoredNBI Item Restriction/Items Ignored
43B – Type of Design/Construction Other, Frames, Arches, Suspension, Stayed Girder, Movables, Tunnel, Culvert, Mixed, Segmental
48 – Length of maximum span 6.1 m (20 ft) < Span Length < 150 m (492 ft)
103 – Temporary Structure Designation
Ignore values where Item 103 = T
NCHRP 12-78
Preliminary PhaseAnalyze NBI Data
16
Software to breakdown data
NCHRP 12-78
Preliminary PhaseAnalyze NBI Data
17
Software to breakdown data
NCHRP 12-78
Preliminary PhaseAnalyze NBI Data
18
400,000+ NBI
Records
Final 1500
Bridge Set
NCHRP 12-78
Vehicle/Bridge Selection
• Vehicle Selection–300+ vehicles to 8
• Bridge Selection–18,000+ bridges to 1500 bridge Sample
• Bulk data change
19
NCHRP 12-78
Vehicle/Bridge Selection
20
Vehicle Selection
•States - ~ 300 vehicles•Panel - divide into regions•Select vehicles from regional groupings
NCHRP 12-78
Vehicle/Bridge Selection
21
Vehicle Selection
• Vehicles analyzed using a utility developed by M&M
• Computes LL moments and shears for SS beams and two spans (equal length)
• Ratio to HL-93 vehicle• Vehicles grouped by region
NCHRP 12-78
Vehicle/Bridge Selection
22
Vehicle Selection
• SW region
0.00
0.50
1.00
1.50
2.00
2.50
0 50 100 150 200 250 300 350 400 450 500
Ra
tio
: T
ruc
k/H
L-9
3
Span (FT)
HI-01 HI-02 HI-03 HI-04 HI-05 HI-06 HI-07 NM-01
NM-02 NM-03 NM-04 NM-05 NM-06 NM-07 NM-08 NM-09
NM-10 TX-01 TX-02 TX-03 TX-04 TX-05
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 50 100 150 200 250 300 350 400 450 500
Ra
tio
: T
ruc
k/H
L-9
3
Span (FT)
HI-03 HI-04 HI-05 HI-06 HI-07 NM-01 NM-02
NM-03 NM-04 NM-05 NM-06 NM-07 NM-08 NM-09
TX-01 TX-02 TX-03 TX-04 TX-05
NCHRP 12-78
Vehicle/Bridge Selection
23
Vehicle Selection
Vehicle GVW Length Schematic
DE-07 80 41
FL-04 80 67
NM-04 55.2 22
NC-21 61 21
TX-04 69 20
Vehicle GVW Length Schematic
DE-07 80 41
FL-04 80 67
NM-04 55.2 22
NC-21 61 21
TX-04 69 20
8k
20 k 20 k16 k 16 k
11' 4' 22' 4'
8 k
18k 18k 18k18k
27' 4' 12' 24'
11k6k
19k 19k
6k9' 4' 4' 4'
18.4k
25.3k 25.3k
16' 4'
12k
21.6k
11'
21.6k
11'
Routine Permit Vehicles
NCHRP 12-78
Vehicle/Bridge Selection
24
Vehicle Selection
Special Permit Vehicles
Vehicle GVW Length Schematic
OR-06 150.5 73.5
IL-01 120 44
WA-02 207 70
13k 15k
21.5k 21.5k 21.5k
11.5' 5.5' 4.5' 30'
21.5k
5'
21.5k
5'
15k
12'
12k
21.5 21.5k 22k
10' 4' 6' 16'
21.5k 21.5k
4'
22k
6' 14'
21.5k 21.5k
4'
22k
6'
20k 20k 20k24k 24k
4' 4' 22' 4'
12k
10'
NCHRP 12-78
Vehicle/Bridge Selection
• Eight (8) vehicles• HL-93 (LRFR)• HS-20 (LFR)• Type 3, 3S2, 3-3
25
Vehicle Selection
NCHRP 12-78
Vehicle/Bridge Selection
26
Bridge Selection
Virtis data• Complex database• 18000+ bridges• How do we reduce to compare
with NBI?
Flatten data to compare with NBI
NCHRP 12-78
Vehicle/Bridge Selection
27
Bridge Selection
Virtis Data AnalysisSame Software for
NBI analysis
NCHRP 12-78
Vehicle/Bridge Selection
28
Bridge Selection
Graphic comparisons (Year built)
VirtisNBI
NCHRP 12-78
Vehicle/Bridge Selection
• Virtis bridges selected by–Year–Span length–Bridge/Material Type–Bridge systems only (no line
girders)29
Bridge Selection
NCHRP 12-78
Vehicle/Bridge Selection
30
Bridge Selection
Bridge Material Total # Girders
Percent %
PS Multispan 238 7.82%PS Simple Span 847 27.83%RC Multispan 105 3.45%RC Simple Span 394 12.95%Steel Multispan 418 13.74%Steel Simple Span 1,041 34.21%Total 3,043 100.00%
NCHRP 12-78
Vehicle/Bridge Selection
31
Bridge Selection
Bridge Type Total # Girders
Percent %
Multi-girder built up 29 0.95%Multi-girder rolled beam
1,056 34.70%
Multi-girder steel plate
374 12.29%
PS box beam 381 12.52%PS I beam 704 23.14%Reinf Concrete slab 204 6.70%Reinf Concrete T beam
295 9.69%
Total 3,043 100.00%
NCHRP 12-78
Vehicle/Bridge Selection
• Modifying Data in Virtis–Small application modify Virtis DB–Effective Flange width–Development length (P/S)–Shear analysis flag–Discard some bridges- choose others
32
Bulk Data Change
NCHRP 12-78
Gathering/Analyzing
• Software used• Process 12-50• Manipulating 12-50 data
33
NCHRP 12-78
Gathering/Analyzing
• Virtis 6.1• BRASS LRFR and LFR• Wyoming/ BridgeTech provided
modifications for 12-50 output
34
Software used
NCHRP 12-78
Gathering/Analyzing
• Total number of BRASS runs• 1500 bridges (3043 girders)• 8 permit vehicles + 1 design +
3 AASHTO loads = 12 vehicles• 2 methods (LRFR – LFR)
35
Software used
NCHRP 12-78
Gathering/Analyzing
3043 x 12 x 2 =73,032 BRASS runs
36
Software used
NCHRP 12-78
Gathering/Analyzing
How do we review 73,032 BRASS runs?
Process 12-50
37
Process 12-50
NCHRP 12-78
Gathering/Analyzing
Process 12-50- Developed under NCHRP 12-50- See NCHRP Report 485 for
details- BRASS uses Process 12-50
38
Process 12-50
NCHRP 12-78
Gathering/Analyzing
Process 12-50
39
Process 12-50
NCHRP 12-78
Gathering/Analyzing
40
Manipulating 12-50 data
• BRASS does not produce all results needed in 12-50 format.
• Created application to read Virtis DB for user input data (e.g. span length, girder spacing, etc.)
• Combine user input/BRASS Process 12-50 results into MS Access database
• Process each girder into a single line of output using project developed software
• Output imported to spreadsheet for further calculation/ plotting.
NCHRP 12-78
Gathering/Analyzing
41
Manipulating 12-50 data
• Databases created for each vehicle for each set of bridges
• Results used to:– Compare dead and live loads– Compare rating factors– Calculate reliability index– Determine if trends exist in data
NCHRP 12-78
Gathering/Analyzing
42
Manipulating 12-50 data
• Simple Span Steel Bridges – Design Vehicle– Moment Ratings for Interior, Composite girders (432 girders)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.00 50.00 100.00 150.00 200.00 250.00
LFR
Rati
ng
Span Length (feet)
Built Up Shapes
Plate Girders
Rolled Shapes
LFR Inventory Rating for HS20 Loading
LRFR Inventory Rating for HL-93 Loading
NCHRP 12-78
Gathering/Analyzing
43
Manipulating 12-50 data
Angle of Skew
Tributary Width (Girder Spacing)
Year of Construction
NCHRP 12-78
Gathering/Analyzing
44
Manipulating 12-50 data
• New checks were noted for LRFR that have significant affect on rating– Longitudinal Steel Stress Rating near ends of
concrete superstructure elements
Without Report ID 85004 With Report ID 85004
NCHRP 12-78
Current Status
45
• Panel has reviewed and provided comments on our ‘Findings’ report
• We are reviewing and replying to the comments
• Scheduled finish date: November, 2010
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