Timber Local Bridge Load Rating and Evaluation

Location:	Minnesota
Posted:	May 22, 2026
Due:	Jun 1, 2026
Agency:	State Government of Minnesota
Type of Government:	State & Local
Category:	Z - Maintenance, Repair or Alteration of Real Property
Publication URL:	To access bid details, please log in.

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MnDOT Contract No. 1062621 - 1062625

Exhibit C: Specifications, Duties, and Scope of Work

PROJECT DESCRIPTION AND BACKGROUND

Short wheelbase trucks are a major component of the US transportation system. Specialized Hauling Vehicles (SHV)

include dump trucks, ready-mix concrete trucks, construction vehicles, solid-waste trucks and other hauling vehicles. The

trucking industry has, in recent years, introduced SHVs with closely spaced multiple axles that make it possible for these

short wheelbase trucks to carry the maximum load of up to nearly 80,000 lbs and still meet the Federal Bridge Formula B

and Minnesota laws. In recognition that the SHV may be overstressing bridges, the American Association of State

Highway Transportation Officials (AASHTO) developed new posting loads for single unit truck SHVs that meet the Federal

Bridge Formula B.

Recent research projects have been investigating impacts of Implements of Husbandry (IoH) on bridges commonly found

on the road system. In recognition that IoH may be overstressing bridges, State’s Bridge Office and State Aid for Local

Transportation Group have prepared a guide based on NCHRP Report 951 – Proposed AASHTO Load Rating Provisions

for Implements of Husbandry, to aid bridge owners in the load rating analysis for IoH vehicles. Until any new State

Statutes are added or updated, enforcement is only possible under Statutes 169.801 Implement of Husbandry and

169.824 Gross Weight Schedule. Meanwhile, load rating analysis for IoH vehicles will give owners the data necessary to

protect their bridges.

MnDOT’s Bridge Office and State Aid for Local Transportation Group have identified county and local bridges as

susceptible to supporting SHV, EV and now IoH vehicles. Some bridges may require posting for SHV and EV vehicles

(posting limits specified in online EV mapping tool), but no specific posting guidance has been formalized for IoH vehicles

to date. Hence, the final bridge list for evaluation in this contract will also include load rating for IoH. The list of bridges

for IoH load rating was based on current operating ratings, IoH notional load, bridge type and rating method.

Work under this Contract involves rating and load posting analysis of bridges on the State’s local system. Services

include new rating analysis, recommendations for posting at or below the legal load, when necessary, bridge field

investigations to insure rating accuracy and conformance with actual field conditions, examine current rating to ensure

conformance with the new posting loads, and a QA Review of ratings.

All bridges will be rated in AASHTOWare BrR 7.7.1.3001. Bridges not compatible with AASHTOWare BrR will be rated

by hand, approved spreadsheet or approved design software.

II. DEFINITIONS

A. Girder System Superstructure: The entire beam framing plan (includes all beams and diaphragms).

B. Girder Line Superstructure: A representative single line beam is analyzed.

C. Truss: An assemblage of members forming a rigid framework. Trusses are most often made up of a series of

triangular panels and are used to support forces such as gravity loads at discrete points with broad open spaces

in between.

D. Truss Main Members: The large section members of the truss. They carry the gravity loads and vertical moving

loads and form the main load carrying framework.

E. Gusset Plate: A one-piece element that connects all members to the joint.

F. Gusset Plate Connection System: One or multiple gusset plates with all splice plates, if any, at same joint.

G. Culvert: A structure that is used primarily to allow water to flow under a road, railroad, trail or similar

obstruction, although a variety of wildlife uses them as passageways. It may be made from a pipe, reinforced

concrete, steel or other materials.

Bridge Types:

A. CCONC BM SPAN

B. CCONC DK GIRD

C. CCONC SLAB SPAN

D. CONC ARCH

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MnDOT Contract No. 1062621 - 1062625

Exhibit C: Specifications, Duties, and Scope of Work

E. CONC BOX CULV

F. CONC DECK GIRD

G. CONC SLAB SPAN

H. CSTL BEAM SPAN

I. CSTL DECK GIRD

J. MASONRY ARCH

K. PRECST BOX CULV

L. PRECST CHAN SPAN

M. PRECST PIPE ARCH

N. PRESTR BM SPAN

O. PRESTR BOX GIRD

P. PRESTR QUAD TEE

Q. STEEL ARCH

R. STEEL BM SPAN

S. STEEL LONG SPAN

T. STEEL PIPE ARCH

U. STEEL PIPE CULV

V. STEEL THRU GIRD

W. TIMB BEAM SPAN

X. TIMB SLAB SPAN

III. RATING ANALYSIS METHODS

A. Girder System Structure Method:

Method where an entire framing plan unit is entered. Rate bridges as a system.

B. Girder Line Structure Method:

Method where applicable line girder data is entered.

IV. WORK TASKS

Work under this Contract includes a rating and load posting analysis of the bridges on county and local highway systems,

an on-site field investigation of each bridge, and a QA Review of the bridges rated. Work will be in conformance with the

following:

A. Information and Data Gathering:

1. Contractor shall examine current Inventory Sheet and Inspection Reports for each bridge. Reports are

available on the MnDOT Bridge Office web site. The Inventory Sheet indicates if a plan is available, where

it can be found, and identifies the current bridge rating.

2. Contractor shall examine bridge files and records at respective county and local Municipal Offices. Plans

and previous rating information are on file for most bridges. Copy all pertinent information. Files for each

of these bridges are also kept at the MnDOT Bridge Office. In most cases these files will contain the same

information. However, in some cases one of them might contain more complete information. When

bridge plans are not available, data will be collected during field investigation (see below).

Note: Contractor is responsible for making arrangements with Counties and Municipalities to examine

and copy files.

3. Some plans are available at MnDOT’s Bridge Office and District Offices.

4. Contractor shall transmit copies of all bridge plans obtained or identified to MnDOT Bridge Inventory

Management Unit (BIMU) to support bridge inventory records. This requirement applies even if the plans

are already available at the MnDOT Bridge Office, District Offices, or other MNDOT repositories. The

Contractor shall ensure that copies of the plans used or obtained are transmitted to BIMU. All submitted

copies will be clear and readable. BIMI will provide access to a MnDOT FTP site for transmission. The

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MnDOT Contract No. 1062621 - 1062625

Exhibit C: Specifications, Duties, and Scope of Work

Contractor may also propose alternative electronic transfer methods, provided the method is compatible

with MnDOT security protocols and approved by MnDOT.

B. Field Investigations:

1. For bridges requiring field inspection under this contract, the Contractor shall notify that governing local

agency and the bridge owner at least two weeks prior to the scheduled bridge visit to inform them of the

planned investigation. A follow up email or phone call will be made by the Contractor to the bridge owner

2 or 3 days before the site visit. Finally, as a reminder, the Contractor shall notify the governing local

agency and the bridge owner on the day of the visit.

2. Conduct a field investigation of each bridge. Inspections will be to the extent necessary to perform an

accurate rating analysis of the bridge.

3. Upon discovering a Critical Finding (or determining that a deficiency is critical), the Contractor shall

immediately notify the local agency Program Administrator and the Bridge Owner. The Contractor shall

assist and support the Program Administrator in initiating the Critical Finding Report in SIMS within 24

hours of identifying the issue and provide all necessary documentation to aid in the reporting process.

Load Rater must determine within 24 hours of the finding to determine if closure or temporary traffic

restrictions (shoulder or lane closures) should be implemented. The load rater and all parties will prioritize

load ratings prompted by Critical Findings by expediting the 3 months load rating completion timeframe.

4. Measure all metal culverts in detail, by hand or by means of modern bridge inspection technologies such

as laser measuring device, drone and photogrammetry, Lidar etc. Follow MnDOT Metal Culvert Inspection

Guidance document. For those bridge inspection technologies that are unable to photograph and

measure below the water surface, hand inspection/measuring and probing will also be required. Because

this contract is federally funded, the use of non-US made drone is prohibited per American Security Drone

Act of 2023.

5. Contractor shall ensure that all inspection results are properly documented and communicated to

Program Administrator and Team Leader responsible for the bridge inventory. Contractor shall utilize

current inspection reports and bridge inventory report (sheet). Annotate each report to document

findings that are pertinent to a rating analysis or that verify no changes.

a) Contractor shall confirm that inspection data, notes, and condition findings have been

successfully transmitted for entry into SIMS.

b) If inspection findings indicate a condition that may require immediate action, Contractor shall

notify local agency Program Administrator and the Bridge Owner within 24 hours of discovery.

6. If substructure damage or deterioration is observed during field inspection, the Contractor shall document

the condition. Conditions that are pertinent to the load rating evaluation, including deterioration, section

loss, damage, or changes in structural behavior, will be clearly noted and considered in the rating analysis.

If severe damage or significant change in bridge condition is observed that may affect structural capacity

or bridge safety, the Contractor shall immediately notify the local agency Program Administrator and the

Bridge Owner. Notification will occur within 24 hours of discovery.

7. There are no plans for some of the bridges. Some bridge description information may be found in previous

rating documents. This information will be verified during inspections. The Contractor shall be responsible

to attain detailed measurements when necessary to document member lengths, spacing, sizes, etc. In

order to conduct the necessary field work, the Contractor shall:

a) Secure all access permits, including those required from railroads. Scheduling of railroad

flaggers will be the responsibility of the Contractor. For bridges over navigable waterways the

Contractor shall also notify the Coast Guard that inspection teams will be working on bridge

elements over or adjacent to waterways.

b) Access to structure elements for field measurements will be by aerial platforms, aerial lifts,

Under Bridge Inspection Units (UBIUs,) bucket trucks, rigging, staging, ladders, walking or

combination thereof. The Contractor shall be fully responsible for determining the overall

method(s) of access and safety of inspectors.

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MnDOT Contract No. 1062621 - 1062625

Exhibit C: Specifications, Duties, and Scope of Work

c) Establish method of access, schedule and provide all necessary access equipment.

d) Safety when conducting field measurements and survey will comply with all applicable pertinent

sections of State and Occupational Safety and Health Administration (OSHA) Standards which

must be strictly adhered to. Failure to comply with all State and OSHA safety requirements will

result in immediate cessation of activities until safety requirements are met.

8. When taking field measurements and survey of the structure, the following restrictions will be adhered to:

a) Inspection of structures in the Twin Cities metro area that require any lane restrictions will

adhere to the State’s Lane Closure Manual as found at:

www.dot.state.mn.us/metro/trafficeng/laneclosure/index.html

b) When the local agency is not able to provide traffic control for bridge access, the Contractor

shall be responsible for providing all traffic control. Traffic control efforts will be coordinated

with the appropriate State’s District level contacts and local agency to determine if a traffic

control plan will be required. If needed a traffic control plan meeting the requirements of the

Federal and the State’s Manual of Uniform Traffic Control Devices (MUTCD) and other State

requirements will be prepared and submitted for approval prior to commencing any work.

c) The Contractor shall notify local and State law enforcement agencies and traffic management

centers at least 72 hours in advance of any proposed lane closures.

9. All inspection work will comply with MnDOT safety standards, MnDOT Bridge and Structure Inspection

Program Manual, Minnesota Advanced Timber Bridge Inspection Field Manual & Supplement, applicable

State and OSHA regulations.

C. Rating Analysis:

1. Following completion of the field investigation for each bridge, the Contractor shall complete the

corresponding load rating analysis and submit rating documentation to the local agency and MnDOT as

soon as practical, but no later than 3 months after the inspection.

2. Perform a new rating analysis for each bridge as specified based on AASHTO Design Trucks, MnDOT Legal

(posting) Vehicles, AASHTO Single Unit Vehicles SU4 through SU7, Minnesota Standard Permit Trucks, 6-

axle (90k) and 7-axle (97k) annual permit trucks, emergency vehicles Type EV2 and Type EV3. In general,

ratings will be based solely on the superstructure however some ratings will require substructure analysis

if serious substructure damage or deterioration is encountered. New rating analysis must be completed

using the latest copy of the MnDOT Form RC-CL, MnDOT PIR-CL or MnDOT Form Truss R.

3. Perform a re-load rating analysis of IoH Tier 1 & Tier 2 vehicles for specified bridges that are compatible

with AASHTOWare BrR, using LRFR method. The rating analysis will not require a site visit if there is no

significant change in the NBI condition ratings and/or structural element condition states of the bridge for

deck, super or sub since the last load rating, and the Contractor shall only annotate and initial the current

load rating form. Reviewing the existing BrR file will be necessary. Also, IoH rating values will be recorded

in Exhibit K spreadsheet.

4. For bridges where load rating analysis cannot be performed due to lack of necessary plan information or

inability to attain a complete field measurement, use a Physical Inspection Rating (PIR) based on

Minnesota Standard Permit Trucks and emergency vehicles Type EV2 and Type EV3. The load rating

engineer must use the inspection information and data, available knowledge of the design live load, live

load history and the current condition of the structure (superstructure and substructure) to support the

PIR. Plans from a similar size, type and vintage bridge structure and with known plan details, may be used

to provide the basis for the PIR evaluation. EV rating factors will be recorded on page 2 of the PIR rating

form. Note: LFR, LRFR, ASR, EV2 and EV3 rating values will be recorded in Exhibit K spreadsheet.

5. All bridges and culverts compatible with AASHTO BrR will be rated in BrR 7.7.1.3001. Visit the

AASHTOWare Bridge Design and Rating Technical Support web page for the list of bridges compatible with

BrR. Bridges not compatible with BrR will be rated by hand, other design software or spreadsheet. In BrR,

the girder system method will be used whenever reasonably feasible.

6. BrR input file will be recorded in LRFR and LFR/ASR method.

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MnDOT Contract No. 1062621 - 1062625

Exhibit C: Specifications, Duties, and Scope of Work

7. All bridges that require calculations will be rated for LRFR method including timber bridges. If LRFR results

in a load posted bridge, ASR (timber bridges) or LFR method may be used to result in a better load rating

and/or eliminate a load posting requirement except for metal culvert which will always be rated in LRFR.

When considering using ASR or LFR, please contact MnDOT’s Project Manager of this contract. Note: LFR,

LRFR, ASR, EV2 and EV3 rating values will be recorded in Exhibit K for the bridge types specified to be

rated. Timber bridges will be load rated for ASR method only

8. All timber abutments/piers in a condition state of 4 will be inspected to determine if a new load rating is

required.

9. Substructure ratings to be performed in accordance with the MnDOT Bridge Load Rating and Evaluation

Manual, section 7.1.4. Incorporate any advanced timber bridge inspection deterioration data into the

rating analysis.

10. Load rating of timber abutment piling to consider axial/flexural interaction due to vertical superstructure

loads and lateral loads from retained earth pressure and live load surcharge

11. Use hand calculations, finite element software, or other computer programs for timber abutment

structural analysis. For timber abutment cap, consider shear, flexure, and bearing limit states as

applicable. For timber abutment pile load rating, consider axial, flexure, and shear limit states as

applicable.

12. Use hand calculations, finite element software, or other computer programs for timber pier structural

analysis. For timber pier cap, consider shear, flexure, and bearing limit states as applicable. For timber

pier pile load rating, consider axial, flexure, and shear limit states as applicable.

13. All metal culverts will be load rated using CMP LRFR Load Rating Spreadsheet that will be provided by

MnDOT. Follow MnDOT LRFR Metal Culvert Spreadsheet Guidance document.

14. Follow the AASHTO Manual for Bridge Evaluation (3rd Edition 2018), AASHTO Standard Specifications for

Highway Bridges, 17th Edition, and State supplemental instructions, Load and Resistance Factor Design

(LRFD), American Institute of Steel Construction (AISC), and all other pertinent AASHTO Specifications and

MnDOT Bridge Load Rating and Evaluation Manual (2023).

15. Use AASHTO Manual for Bridge Evaluation (3rd Edition 2018) to rate the gusset plate connection system

of main members at all truss joints.

16. Perform a complete QC check of each new load rating which includes but not limited to, the load rating

form which includes the load posting sign type and values (prior to owner obtaining load posting signs),

the load rating & load posting report, computer input, output and hand calculations, inspection report.

Perform a complete QC check of each bridge that requires re-load rating which includes but not limited to,

the load rating form which includes the load posting sign type and values (prior to owner obtaining load

posting signs), the load rating, computer input, output and hand calculations, inspection report. Approved

non-BrR software accuracy must be verified by Contractor’s internal QA/QC process.

17. Contractors will use the current MnDOT load rating forms for all work performed under this contract. The

most up-to-date versions of the forms will be obtained from the MnDOT Bridges and Structures website.

Contractors are responsible for verifying that the latest versions are used at the time of analysis and prior

to submittal. Use of outdated forms will not be accepted. All rework required to update to the current

forms will be performed at no additional cost to MnDOT and will not be grounds for schedule extension

unless otherwise approved by MnDOT.

D. Rating/Posting Report Coordination with Bridge Owner:

1. When a bridge requires load posting, the Contractor must verbally discuss with the bridge owner

(county/city/township) their options. This may include the available load posting sign options, for

example the SHV sign, R12-5M, as an option. Another option may include re-rating the bridge from LRFR

to LFR for a better load rating, or the owner may elect to perform an emergency repair to carry legal loads,

establish a partial lane closure, etc.

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This is the opportunity summary page. It provides an overview of this opportunity and a preview of the attached documentation.

Timber Local Bridge Load Rating and Evaluation

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See also