Rating and Posting Bridges for SHVs

-- Iowa Timeline

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Ping Lu and Scott Neubauer

The Office of Structures and BridgesIowa Department of TransportationPing.lu@dot.iowa.gov Scott.Neubauer@dot.iowa.gov515-239-1290 (515) 239-1165

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SHVs (Special Hauling Vehicles) Closely-spaced multi-axle single unit trucks

Comply with Bridge Formula B Legal in Iowa Design truck HS20 might not envelope SHVs, especially for short span

bridges

Examples: dump trucks, construction vehicles, solid waste trucks and other hauling trucks

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Truck Models for SHVs Developed and adopted by

AASHTO in 2005

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FHWA Timeline (11/15/2013 Memo)

Any bridge needing to be re-rated should include SHVs Group 1, rated before 12/31/2017

Shortest span <= 200 ft; and Operating Rating (ASR, LFR) for Type 3 < 33 Tons, Type 3S2 < 47 Tons,

or Type 3-3 < 52 Tons (all English Tons); or LRFR, legal load rating factor for Type 3, Type 3S2, or Type 3-3 < 1.3

Group 2, rated before 12/31/2022 Bridges not in group 1

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Concerns for FHWA Timeline Minimum span is not an NBI item The cutoffs were measured in terms of legal rating

not necessarily provided by current load rating report

don’t know which bridge needs to be re-rated don’t know when a bridge needs to be re-rated

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Questions to be Solved for SHV Rating

Bridges currently posted: need to update posting? Bridges not currently posted : How many need to be posted? Determine a practical timeline to rate Iowa bridges for SHVs

Parametric study (simple span bridges) State bridge study (more than 3,000 Iowa state owned

bridged were rated)

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Parametric Study Simple span ranges from 20 ft to 300 ft SHV’s, H20, HS20, and Iowa legal trucks

Name Picture Weight

SU4

54 k

SU5

62 k

SU6

69.5 k

SU7

77.5 k

Name Picture Weight

SU4-2nd

53 k

SU5-2nd

57.5 k

SU6-2nd

63 k

SU 7-2nd

64.5 k

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Parametric Study (Moment)

0.9

0.95

1

1.05

1.1

1.15

1.2

1.25

1.3

20 30 40 50 60 70 80 90 100 110 120 130 140 150

Ratin

g Ra

tio w

ith R

egar

d to

Typ

e 4

Truc

k -M

Span Length (ft)

SU4 SU5 SU6 SU7

𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑆𝑆𝑆𝑆𝑆𝑆 (𝑇𝑇𝑇𝑇𝑅𝑅𝑇𝑇)𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑇𝑇𝑦𝑦𝑦𝑦𝑦𝑦 4 (𝑇𝑇𝑇𝑇𝑅𝑅𝑇𝑇)

= 𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚−𝑇𝑇𝑦𝑦𝑦𝑦𝑦𝑦 4

𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚−𝑆𝑆𝑆𝑆𝑆𝑆

𝑊𝑊𝑆𝑆𝑆𝑆𝑆𝑆𝑊𝑊𝑇𝑇𝑦𝑦𝑦𝑦𝑦𝑦 4

• Ratio > 1 for all SHVs except SU4• SU7 Rating/Posting (Tons) > SU6 > SU5 > Type 4 > SU4

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Parametric Study (Shear)

• Ratio > 1 for all SHVs except SU4• SU7 Rating/Posting (Tons) > SU6 > SU5 > Type 4 > SU4

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

20 30 40 50 60 70 80 90 100 110 120 130 140 150

Ratin

g Ra

tio w

ith R

egar

d to

Typ

e 4-

V

Span Length (ft)

SU4

SU5

SU6

SU7

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Bridges Currently Posted Moment control:

The rating/posting ratio for SU4 to Type 4 truck is (0.95, 1) The posting difference < 1.36 Tons (27.25 Tons x 5% = 1.36 Tons) and

within 5% margin. Current posting is acceptable

Shear Control The rating/posting ratio for SU4 to Type 4 truck is (0.93, 1) The posting difference < 1.90 Tons (27.25 Tons x 7% = 1.90 Tons) and

within 7% margin. Current posting is acceptable

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Bridges Not Currently Posted HS20 operating rate < 45.0 Tons -> need to be re-rated and possibly

posted for the closest SHV

25.00

30.00

35.00

40.00

45.00

20 30 40 50 60 70 80 90 100 110 120 130 140 150

Cut

off O

pera

ting

Rat

ing

-H

S20

(T

ons)

Span Length (ft)

SU4

SU5

SU6

SU7

Type 4

Re-rate and post for SU6

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Conclusions from Parametric Study Simple span bridges* with HS20 operating rating > 45.0 Tons

No SHV rating is required

Simple span bridges currently posted The posting is conservative for SHVs except SU4 The posting difference between Type 4 and SU4 is smaller than

1.36 tons (within 5% margin) if bending controls; 1.9 tons (within 7% margin) if shear controls

Current posting is acceptable and re-rating is not required

Simple span bridges not currently posted and HS20 operating rating < 45.0 Tons Need to be re-rate and possibly post for the controlling SHV following

the timeline suggested by Iowa DOT

* Include PPCBs; only beam type bridges

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Results from State Bridge Check More than 3,000 Iowa state owned bridges were checked

No bridge with HS20 operating rating > 45.0 Tons (actual number is 43.2 Tons) need to be posted for SHV’s

All bridges posted for Type 4 need to be posted for SHV’s and the posting is controlled by SU4, which, in maximum, is 0.96 Tons lower than Type 4 posting. -> within 1.00 ton limit, so current posting is acceptable

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Proposed Limits for SHV Rating

HS20 operating rating < 45.0 Tons ; and Not currently posted Number of bridges within limits

Number of bridges not needing re-ratingOperating Rating > 45.0 Tons Currently Posted

Special/Multi-Span Simple Span/PPCB Special/Multi-Span Simple Span/PPCBLocal 2971 3384 1291 2493State 1227 1824 10 4

Operating Rating <= 45.0 Tons & Not PostedSpecial/Multi-Span Simple Span/PPCB

Local 2587 2886State 174 90

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Proposed Iowa DOT Timeline Group 1, before 12/31/2016 (can be done by the ratio of HS20 operating

rating; ratio table will be provided) Simple span beam type bridges + multi-span PPCBs (not posted)

2,886 local bridges and 90 state bridges

Group 2, before 12/31/2020 Multi-span (not posted)

2,351 local bridges and 171 state bridges

Simple span special bridges (arch, truss, etc) (not posted) 236 local bridges and 3 state bridges

Group 3, before 12/31/2022 Bridges not belonging to Group 1 or Group 2

Bridges > 45 tons or Posted Number would be 0 if FHWA can confirm the requested items 6,355(2,971+3,384) local bridges & 3,051 (1,227+1,824) state bridges (>45 tons) 3,784 local bridges and 14 state bridges (posted)

Any group, if re-rating is warranted, re-rating should include SHV’s

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Iowa DOT SHV Rating Actions Rate 1987 and newer standards

H-standard– done except 1994-std Propose for IHRB research project to rate J-standard and RS-std-04

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Comments and Questions?