Rating of Local Bridges for SHVs
Using Virtis Software
Virtis/Opis User Group Meeting
August 3-4, 2010
Moises C. Dimaculangan, P.E.
Minnesota Department of Transportation
Presentation Overview
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Specialized Hauling Vehicles (SHVs)
Bridge Rating for SHVs
Rating Contract
Rating Analysis
Challenges
Future Project
Specialized Hauling Vehicles
What is a SHV?
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Single unit (SU) trucks with closely-spaced
multiple axles
Maximum load of up to nearly 80,000 lbs
Must meet the Federal Bridge Formula B
Considered legal and typically allowed
unrestricted operation
Examples: Gravel Trucks, Redi Mix Trucks, Milk
Trucks
Specialized Hauling Vehicles
54 kips
18’
SU4
69.5 kips
26’
SU6
62 kips
22’
SU5
77.5 kips
30’
SU7
Bridge Rating for SHVs
 Why is bridge rating important?
• SHVs are increasingly common on our roadways
• Effects on short span bridges
• Fulfill National Bridge Inspection Standards (NBIS)
requirements
• Update local bridge rating database
Bridge Rating for SHVs
 Why is bridge rating important? (cont.)
• Create a consistent summary of load carrying
capacities of all state bridges
• Used for bridge posting and for issuing overweight
permits
• Monitor safety of bridges over time
• Determine when rehabilitation or replacement is
needed
Bridge Rating for SHVs
Minnesota legal trucks used to determine load posting
Type M3
48 kips
16’
Type M3S2-40
80 kips
51’
Type M3S3
80 kips
47’
Rating Contract
Funding - $800,000 from FHWA and State Aid
14,786 bridges in the local system
Bridge selection process
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Operating Rating < HS 27
Rating date, 30+ years old
Rating Method
Bridge type
Local agencies input - 2 year replacement
581 bridges selected for rating
ID Number
106
109
206
209
301
401
501
511
520
521
522
701
709
Rating Contract
Bridge Type
No. of Bridges
Reinforced Concrete Deck Girder (T-Beam)
13
Reinforced Concrete Slab Span
54
Reinforced Concrete Continuous Deck Girder
65
Reinforced Concrete Continuous Slab Span
1
Steel Beam Span
109
Continuous Steel Beam Span
42
Prestressed Concrete Beam Span
14
PreCast Concrete Channel Span
24
Prestressed Concrete Double Tee
1
Prestressed Concrete Quad Tee
10
Prestressed Concrete Bulb Tee
4
Timber Beam Span
87
Timber Slab Span
157
Total # of Bridges =
581
Rating Contract
$1400 ±/bridge
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Data gathering, field investigation,
inspections, rating analysis
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4 bridge rating contracts
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$200,000/contract
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Bonestroo – national firm
HDR – national firm
LHB – local firm
WSN – local firm
Rating Contract
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Phase I
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May 2010 – May 2011
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Impact of the project is
statewide
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Heaviest concentration of
work located in southern
Minnesota
Rating Contract
Scope of work
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Information and Data Gathering
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Examine current inventory rating sheets and
inspection reports
Examine bridge files and records
Field Investigations
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Bridge inspections
Field measurements
Rating Analysis
Virtis 6.1
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Bridge will be rated in Virtis
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Provides consistency in rating
Bridges not compatible with Virtis will be rated by
hand or other design approved software such as MDX
Rating analysis based on AASHTO Design Trucks,
MnDOT Legal (posting) Vehicles, and SHV’s
Ratings must meet AASHTO Manual for Bridge
Evaluation, MnDOT LRFD Bridge Design Manual
requirements
Perform a complete QC of each rating
Rating Analysis
 Virtis 6.1 (cont.)
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Rating method
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Reinforced and prestressed concrete
bridges will be rated for both LFR and
LRFR methods
Steel bridges - LFR method
Timber bridges - ASR method
Rating Analysis
 Virtis 6.1 (cont.)
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Why use Virtis for local bridges?
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Consistent with TH system
Ease of permitting with local bridges
Ease of re-rating bridges when a change in
rating codes, bridges condition or truck
configuration occurs
Challenges
No plans available
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Timber and steel bridges
Prestress concrete bridges
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Physical Inspection Rating (PIR)
No Access
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Bridge No. 88494
Built in 1950
Concrete Slab Span – 12ft in length
Operating Rating = HS18, Date: 1973
Br. No. 88494
Challenges
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Deteriorated Substructures
• Bridge No. L3612
• Built in 1958
• Timber Slab Span – 26ft in length
• Operating Rating = HS26, Date: 1974
Br. No. L3612
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Abutment
pile failure
from earth
pressure
Br. No. L3612
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Deteriorated
abutment
pile
Challenges
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Unique Design
• Bridge No. 92079
• Built in 1958
• Steel Beam Span – 16ft in length
• Operating Rating = HS20, Date: 1973
Br. No. 92079
Br. No. 92079
Br. No. 90343
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Concrete
slab span
20ft long
Built in 1923
Operating
rating = HS19
Rating Date:
1973
No plans
available
Br. No. 90343
Br. No. 94063
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Steel beam span
17ft long
Built in 1941
Operating rating
= HS20
Rating Date: 1973
Br. No. 94063
Br. No. 94063
Future Project
Phase II
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$500,000 budget, 2011-2012 contract
FHWA audit of load ratings and postings
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Emphasis on load rating updates
Help locals with permitting by giving them
procedures and guidelines
Accommodate changing truck weights
Questions?