NCHRP 12-78 VOBUG Nashville– 2010 NCHRP 12-78 Evaluation of Load Rating by LRFR Mark Mlynarski,...

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

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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

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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?

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NCHRP 12-78

Background

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• 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

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• 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

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NCHRP 12-78

Preliminary PhaseSurvey

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• Surveys sent to all states• Questions related to load

rating procedures• Solicit vehicle information and

bridge data (Virtis)

NCHRP 12-78

Preliminary PhaseSurvey

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• Responses to survey (33 total) Manitoba

NCHRP 12-78

Preliminary PhaseCollect Virtis Data

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AASHTOWare Bridge Data Manitoba

State#

Bridges

Alabama 3139Illinois 3232Michigan 378Missouri 4644New York 5412Oklahoma 44S. Dakota 1135Tennessee 53

Total 18038

NCHRP 12-78


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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


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• 18,000 + Virtis bridges• 1500 from these

• 300 + vehicles• 8 selected

NCHRP 12-78

Preliminary PhaseAnalyze NBI Data

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• 2008 NBI data used• Software to analyze NBI DB• Certain records ignored

NCHRP 12-78


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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


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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


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Software to breakdown data

NCHRP 12-78


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Software to breakdown data

NCHRP 12-78


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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

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NCHRP 12-78


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Vehicle Selection

•States - ~ 300 vehicles•Panel - divide into regions•Select vehicles from regional groupings

NCHRP 12-78


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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


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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


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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


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


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Vehicle Selection

Special Permit Vehicles


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


• Eight (8) vehicles• HL-93 (LRFR)• HS-20 (LFR)• Type 3, 3S2, 3-3

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Vehicle Selection

NCHRP 12-78


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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


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Bridge Selection

Virtis Data AnalysisSame Software for

NBI analysis

NCHRP 12-78


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Bridge Selection

Graphic comparisons (Year built)

VirtisNBI

NCHRP 12-78


• Virtis bridges selected by–Year–Span length–Bridge/Material Type–Bridge systems only (no line

girders)29

Bridge Selection

NCHRP 12-78


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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


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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


• Modifying Data in Virtis–Small application modify Virtis DB–Effective Flange width–Development length (P/S)–Shear analysis flag–Discard some bridges- choose others

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Bulk Data Change

NCHRP 12-78

Gathering/Analyzing

• Software used• Process 12-50• Manipulating 12-50 data

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NCHRP 12-78

Gathering/Analyzing

• Virtis 6.1• BRASS LRFR and LFR• Wyoming/ BridgeTech provided

modifications for 12-50 output

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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)

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Software used

NCHRP 12-78

Gathering/Analyzing

3043 x 12 x 2 =73,032 BRASS runs

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Software used

NCHRP 12-78

Gathering/Analyzing

How do we review 73,032 BRASS runs?

Process 12-50

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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

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Process 12-50

NCHRP 12-78

Gathering/Analyzing

Process 12-50

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Process 12-50

NCHRP 12-78

Gathering/Analyzing

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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

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• 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

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• 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

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Angle of Skew

Tributary Width (Girder Spacing)

Year of Construction

NCHRP 12-78

Gathering/Analyzing

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• 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

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• Panel has reviewed and provided comments on our ‘Findings’ report

• We are reviewing and replying to the comments

• Scheduled finish date: November, 2010

NCHRP 12-78 VOBUG Nashville– 2010 NCHRP 12-78 Evaluation of Load Rating by LRFR Mark Mlynarski,...

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