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Kansas Local Bridge Rating Program
Kansas Local Bridge Rating Program
Presentation Outline
• Past and Present Requirements Leading to KLBRP• KDOT Project Manager – Colby Farlow, P.E.
• Program Details• Consultant Team Project Manager – Lindsay Madsen, P.E.
• Load Rating Local Bridges• Consultant Team Project Manager – Scott Moeder, P.E
• Arch Bridge Load Rating • TranSystems Team Sub-Consultant – Mark Johnston, P.E
– Keith Wetter, P.E
• Bridge Collapses
• Investigations
• Findings
LAWMAKERS ATTEMPTING TO ENACT LEGISLATION OR REGULATIONS TO PREVENT IT FROM HAPPENING AGAIN
• State by State Audit from FHWA
• For Kansas…..• State System – Minimal List of Items• Local System – Bullet Point List of Required Improvements for
Compliance with the NBIS• Plan of Action Submitted by KDOT BLP
• Standardization of Bridge Inspection Program• Standard Bridge Inspection Scopes of Services• Manuals• Inspector Requirements• Inspection Data Entry• Need for Statewide Programs
• 15 (+) Years (2010-2015)• 5 (+) Consultants Involved• Identify all Scour Susceptible Bridges
• Evaluate scour vulnerability• Prepare scour plan of actions where necessary
• Identify all Fracture Critical Bridges (Approx. 550 Bridges)• Perform first fracture critical inspection• Load rate bridges where deemed necessary
• 10 Year Program (2015-2024)• 7 Consultants Involved• Load Rate all remaining local structures (about 19,000)• Next step to meet current regulations• Updates local system for changes to Legal Loads• Delivers a valid, legal load rating for every local structure
Previous Load Ratings Projects (1990s)
• Very few included Special Haul Vehicles• No consistency from consultant to consultant
• Assumptions• Load Rating Methods• Stamped/Sealed by P.E.• Reporting methods• Not all counties/bridge owners took advantage of the
program• No ability to easily modify load ratings• Structures w/o plans – some ultra-conservative;
others less so
Special Haul Vehicles (SHVs)
Applicable on all bridges unless explicitly excluded by State Law…Kansas Laws do not exclude SHVs.
NRL – Notional Rating Load
• TranSystems team project manager
Lindsay Madsen
• GBA team project manager
Scott Moeder
~19,000 Off-System Bridges Statewide
Two Teams
Completed During the 1st Year
• Step 1 – Data Gathering
• Step 2 – Field Investigation
• Step 3 – Load Rating
Data Gathering
Data Gathering
Field Investigation
Load Rating
American
Association of
State
HIGHWAY and
Transportation
Officials
Our Project Guidelines -
Is it a Highway???
Is it a Highway???
Is it a Highway???
Is it a Highway???
Is it a Highway???
Some common gray areas:
- What to do with exterior girders?
- When is something one lane vs. two lane?
- When is a top flange laterally braced?
- How much overburden is too much?
Code Interpretation Areas
Close the bridge? Or not?
2 lane distribution factor for timber deck: S/3.75 = 0.53 wheels
Interior Girder:
Exterior Girder:
LLDF = 1.0?
Timber Deck with a cantilever?
ADT = 10 vpd
Interior Girder:1 lane distribution factor for timber deck: S/4.0 = 0.50 wheels
Close the bridge? Or not?
Exterior Girder:
LLDF = 1.0?
ADT = 20
Roadway width = 18’-0”
One lane or two?
S/5.5 or S/7 ?
When is a flange laterally braced?
Yes – braced. No – not braced.
Maybe?
Overburden
Overburden
Overburden
Overburden
Overburden
The bridge is….where?
The bridge is here.
Soil Weight = 21’ x 28’ x 4.0’ x 120 pcf = 282,240 lbs!(almost 4 - HS20 trucks)
Girders provided by ATSF Railroad – used railcar superstructure
Other unusual structures…
- One lane bridge due to timber runners/signed one lane
- Used a distribution factor of 1 wheel per railcar
- Modeled as a series of built up sections
Other unusual structures…
o One of the Oldest Construction Materials – Stone
o ~ 1,700 In-Service Masonry Arch Bridges in the U.S.
o 50% Built Prior to 1910
Modified MEXE Arch Assessment Method
Modified MEXE Arch Assessment Method
o Majority of Masonry Arches Located in NE U.S.
o KDOT Bridge Database : Between 280-650 Arches
o Arch Load Rating Challenges
• No As-Built Plans
• Unknown Fill & Arch Properties
• Interaction of Fill with Barrel
• Unknown Effects of Material
Degradation
Modified MEXE Arch Assessment Method
o Arch Load Rating Options
• Non-Destructive Evaluation
or Ground Penetrating Radar
• Collect/Test Material Properties
• Proof Test or Live Load Test
• Finite or Discrete Element Analysis
• Empirical Load Rating Method
U.K.’s Modified MEXE Method
Modified MEXE Arch Assessment Method
o MEXE (Military Engineering Experimental Establishment)
• MEXE/Predecessors – Numerous R&D Tasks
Earth Moving Techniques
Road & Airfield Construction Equipment
Crossing Wet & Dry Gaps
Developed Bailey Bridge
o MEXE Method Evolved from
1930s Field & Lab Tests
o During WW II, Needed Quick
Field Method for Military Vehicles
Modified MEXE Arch Assessment Method
12m span arch with a 1m total crown can
carry 27 Tonnes
Modified MEXE Arch Assessment Method
o Modified MEXE Method
• First Published in 1997
• Used by the United Kingdom
currently as main method for
assessments of masonry
filled/solid spandrel arches
o Modified MEXE Method Description
• Assesses the load capacity of the Barrel of the Arch only
Does not cover deficiencies in other portions of bridge (spandrel
walls, wing walls, foundation, etc.)
• Directly determines the allowable 2-axle tandem load
VALID
NOT VALID
Modified MEXE Arch Assessment Method
• Modifications to this load are then made for
Arch Proportions
Barrel Material and Fill Type
Condition of the Barrel
• Conversion to Allowable Gross Vehicle weights for various vehicles
• Requires structure details
obtained from a site visit
Span
Rise of Arch at
Crown/Quarter Points
Arch thickness
Avg. fill depth at Crown
Modified MEXE Arch Assessment Method
o Positive Items to Note
• Allows for Concrete Arches if plans/design not available
• Descriptions/Photo Guide for various Condition Factor values
Modified MEXE Arch Assessment Method
o Positive Items to Note (Cont.)
• Accounts for many aspects of
the arch construction and
condition that other methods
could not readily incorporate
• Provides means to account for
single and multiple axle
tandems
• Standardized Template can be
Developed for Rating
Modified MEXE Arch Assessment Method
o Positive Items to Note (Cont.)
• Method is equivalent to an Allowable Stress Inventory Rating (ASR)
• Consistent with the requirements of the AASHTO MBE
• Masonry to be evaluated by ASR Method
• No separate Operating Rating : OR = IR
• LRFR and LFR in the MBE require use of ASR for masonry
structures
Modified MEXE Arch Assessment Method
o Limitations to Note
• Assumes Adequately Fixed Abutments
• Span Range Limit 5 ft. to 59 ft.
• Total Crown Thickness Range 10” to 70”
• Not Applicable if Arch is Flat or Appreciably Deformed
Modified MEXE Arch Assessment Method
o Evaluation Accomplishments
• Created Conversion Table for NBI Culvert Rating
(Item 62) to MEXE Condition Factor
• Developed Modification Factors to Convert
2-Axle Tandem Load to AASHTO MBE Vehicles
• Developed Field Data Forms
• Developed Excel File for Load Rating All Vehicles
Modified MEXE Arch Assessment Method
o Beta Test Results
• 9 Arch LR’s Completed in SE Kansas
8 Concrete, 1 Stone
1 Closure, 5 Load Posting Reductions, 3 No Change
• Low Fill – Lower Rating
Lower Fills Don’t Distribute Load to Entire Arch
o Arch Load Ratings Statewide to Begin Fall/Winter 2017
References: Department of Transport London, UK Design Manual for Roads and Bridges Vol. 3 Sec. 4, Parts 3 &4 BD 21/01 and BA 16/97 Amend. NO. 2, BridgeHunter.com (background photo), Connecticut AHS (Arch images), and Structure Mag. 5/15 article
Modified MEXE Arch Assessment Method
QUESTIONS?
