11

Mn/DOT BridgesMn/DOT BridgesLegislative Staff BriefingLegislative Staff Briefing

Bridge Design and Bridge TypesBridge Design and Bridge Types

Bridge Inspection ProgramBridge Inspection Program

Bridge TerminologyBridge Terminology

Bridge Crews and Contract Work Bridge Crews and Contract Work

Current Bridge Structural Condition and TrendsCurrent Bridge Structural Condition and Trends

Bridge Preservation InvestmentsBridge Preservation Investments

February 5, 2008February 5, 2008

Bridges Are Designed Bridges Are Designed According to a National CodeAccording to a National Code

American Association of State Highway and American Association of State Highway and Transportation Officials (AASHTO) “LRFD Transportation Officials (AASHTO) “LRFD Bridge Design Specification” is the governing Bridge Design Specification” is the governing code.code.

All 50 states participate in code development All 50 states participate in code development and annual updating.and annual updating.

Development of the first national bridge design Development of the first national bridge design code began in the 1920’s and was published in code began in the 1920’s and was published in 1931.1931.

Reflects the combined experience of 50 states. Reflects the combined experience of 50 states.

Concrete Box CulvertsConcrete Box Culverts

ConcreteConcrete

Steel BeamsSteel Beams

Concrete slab for Concrete slab for shorter spans.shorter spans.

Prestressed beams Prestressed beams for intermediate for intermediate spans with straight spans with straight alignment.alignment.

Steel beams for Steel beams for intermediate/long intermediate/long spans or curved spans or curved alignment. alignment.

Steel or concrete Steel or concrete box girders for box girders for major spans.major spans.

Other types for very Other types for very long spans and long spans and “signature” bridges.“signature” bridges.– ArchArch– SuspensionSuspension– Cable-stayedCable-stayed– ExtradosedExtradosed

Safety Factors in Bridge Safety Factors in Bridge Design Design

Bridges are intentionally over-designed to provide a Bridges are intentionally over-designed to provide a safety factor for many issues including the following:safety factor for many issues including the following:

With a 75-100 year service life, traffic may increase With a 75-100 year service life, traffic may increase in frequency or weight.in frequency or weight.

Materials may have slight imperfections from Materials may have slight imperfections from specificationsspecifications

Tolerances in construction or fabrication may cause a Tolerances in construction or fabrication may cause a bridge component to be slightly different than bridge component to be slightly different than designed.designed.

Steel will corrode during the bridge lifetime and loose Steel will corrode during the bridge lifetime and loose some thicknesssome thickness

Deterioration of concrete, steel, timber Deterioration of concrete, steel, timber

Who Designs TH Bridges?Who Designs TH Bridges?

Mn/DOT Bridge Office (in Oakdale) has a Mn/DOT Bridge Office (in Oakdale) has a preliminary design unit, hydraulic unit, preliminary design unit, hydraulic unit, cost estimating unit and five final design cost estimating unit and five final design units to design bridges across the state.units to design bridges across the state.

In-house, Mn/DOT is staffed to design In-house, Mn/DOT is staffed to design for about $40 M-$50 M bridge for about $40 M-$50 M bridge program/year.program/year.

Program above this annual amount is Program above this annual amount is sent out to consultants.sent out to consultants.

InspectionsInspections

Bridge Inspections, generalBridge Inspections, general Bridge Inspection Cycles – Bridges are inspected Bridge Inspection Cycles – Bridges are inspected

once every two years per National bridge once every two years per National bridge Inventory System. In Minnesota, if the condition Inventory System. In Minnesota, if the condition of the deck, superstructure or substructure is of the deck, superstructure or substructure is rated “4” or less, bridges are inspected annually.rated “4” or less, bridges are inspected annually.

Fracture critical bridges get an in-depth Fracture critical bridges get an in-depth inspection at least once every two years.inspection at least once every two years.

Mn/DOT Bridge Inspectors – Mn/DOT has 75 Mn/DOT Bridge Inspectors – Mn/DOT has 75 certified inspection team leaders. These certified inspection team leaders. These inspection team leaders have taken three weeks inspection team leaders have taken three weeks of FHWA approved Bridge Inspector training.of FHWA approved Bridge Inspector training.

Bridge Inspections, cont’dBridge Inspections, cont’d Equipment used for inspection - inspection equipment Equipment used for inspection - inspection equipment

can include snooper trucks, aerial manlifts, ladders, can include snooper trucks, aerial manlifts, ladders, measuring devices and various tools.measuring devices and various tools.

In-depth inspections use ultrasonic testing, die In-depth inspections use ultrasonic testing, die

penetrant, and magnetic particle test methods and a penetrant, and magnetic particle test methods and a video scope in order to detect cracks and/or corrosion.video scope in order to detect cracks and/or corrosion.

Critical Deficiency – any condition discovered during a Critical Deficiency – any condition discovered during a scheduled bridge inspection that threatens public scheduled bridge inspection that threatens public safety and, if not promptly corrected, could result in safety and, if not promptly corrected, could result in collapse or partial collapse of the structure. When collapse or partial collapse of the structure. When inspectors report critical findings, immediate actions inspectors report critical findings, immediate actions are taken to further assess the situation and to repair are taken to further assess the situation and to repair or close the bridge.or close the bridge.

What Are Inspectors Looking What Are Inspectors Looking For?For?

Deterioration of bridge members such as:Deterioration of bridge members such as: - cracked or spalled concrete- cracked or spalled concrete

- corrosion of steel such that thickness is lost - corrosion of steel such that thickness is lost - corrosion that is causing distortion in a joint- corrosion that is causing distortion in a joint

Assess condition of paint systemsAssess condition of paint systems Distortion of members such as bowing not Distortion of members such as bowing not

aligned as originally builtaligned as originally built Scour from water flow around foundationsScour from water flow around foundations Leaking jointsLeaking joints Support piers that are tilting or movingSupport piers that are tilting or moving

Example of spalled concreteExample of spalled concrete

Example of corroded steel Example of corroded steel girdergirder

Example of tilting pierExample of tilting pier

Governor’s Inspection ProgramGovernor’s Inspection Program

TH System:

3,875 Routine and FC Inspections

270 By Consultants

Local System

141 FC inspections

43 By Consultants

As of December 20th all State Bridge inspections are up to date.

Bridge TerminologyBridge Terminology

Condition ratingCondition rating – overall assessment of the – overall assessment of the physical condition of the deck, superstructure physical condition of the deck, superstructure or substructure, range from 0 to 9.or substructure, range from 0 to 9.

Sufficiency rating (SR) Sufficiency rating (SR) — Sufficiency rating — Sufficiency rating is a computed numerical value that is used to is a computed numerical value that is used to determine eligibility of a bridge for Federal determine eligibility of a bridge for Federal funding. The sufficiency rating formula result funding. The sufficiency rating formula result varies from 0 to 100. The formula includes varies from 0 to 100. The formula includes factors for structural condition rating, bridge factors for structural condition rating, bridge geometry, and traffic considerations. geometry, and traffic considerations.

National Bridge InventoryNational Bridge Inventory Condition Ratings Condition Ratings

9 – Excellent9 – Excellent 8 – Very Good8 – Very Good 7 – Good - No problems noted.7 – Good - No problems noted. 6 – Satisfactory – Some minor 6 – Satisfactory – Some minor

problems.problems. 5 – Fair – All primary structural 5 – Fair – All primary structural

elements are sound but may have elements are sound but may have minor section loss, cracking, spalling, minor section loss, cracking, spalling, or scour.or scour.

National Bridge InventoryNational Bridge Inventory Condition Ratings, cont’d Condition Ratings, cont’d

4 – Poor – Advanced section loss, deterioration, 4 – Poor – Advanced section loss, deterioration, spalling or scour.spalling or scour.

3 – Serious – Loss of section, deterioration, 3 – Serious – Loss of section, deterioration, spalling or scour have seriously affected the spalling or scour have seriously affected the primary structural components.primary structural components.

2 – Critical – Advanced deterioration of primary 2 – Critical – Advanced deterioration of primary structural elements.structural elements.

1 – Imminent Failure – Major deterioration or 1 – Imminent Failure – Major deterioration or section loss in critical structural components. section loss in critical structural components. Bridge is closed to traffic, but corrective action Bridge is closed to traffic, but corrective action may put it back in light service.may put it back in light service.

0 – Failed – Out of service, beyond corrective 0 – Failed – Out of service, beyond corrective action.action.

Summary of Sufficiency Rating Summary of Sufficiency Rating (SR) Factors(SR) Factors

1. Structural Adequacy & Safety (55% max)2. Serviceability & Functional Obsolescence (30% max)3. Essentiality for Public Use (15% max)

Summary of Sufficiency Rating Summary of Sufficiency Rating (SR) Factors(SR) Factors

1. Structural Adequacy & Safety (55% max) – includes 1. Structural Adequacy & Safety (55% max) – includes superstructure, substructure, culverts, and inventory superstructure, substructure, culverts, and inventory rating.rating.

2. Serviceability & Functional Obsolescense (30% max) 2. Serviceability & Functional Obsolescense (30% max) – includes number of lanes on the structure, Average – includes number of lanes on the structure, Average Daily Traffic (ADT), approach roadway width, structure Daily Traffic (ADT), approach roadway width, structure type, bridge roadway width, vertical clearance over type, bridge roadway width, vertical clearance over deck, deck condition, structural evaluation, deck deck, deck condition, structural evaluation, deck geometry, under-clearances, waterway adequacy, geometry, under-clearances, waterway adequacy, approach roadway alignment, STRAHNET highway approach roadway alignment, STRAHNET highway designation.designation.

3. Essentiality for Public Use (15% max) – includes 3. Essentiality for Public Use (15% max) – includes detour length, ADT, and STRAHNET highway detour length, ADT, and STRAHNET highway designation.designation.

Bridge Terminology, cont’dBridge Terminology, cont’dStructurally deficient (SD)Structurally deficient (SD) — Bridges are — Bridges are

classified as “structurally deficient” if they have classified as “structurally deficient” if they have a general condition rating for the deck, a general condition rating for the deck, superstructure, substructure or culvert as 4 or superstructure, substructure or culvert as 4 or less or if the road approaches regularly overtop less or if the road approaches regularly overtop due to flooding. The fact that a bridge is due to flooding. The fact that a bridge is structurally deficient structurally deficient does notdoes not imply that it is imply that it is unsafe. unsafe.

Functionally obsolete (FO) Functionally obsolete (FO) — a functionally — a functionally obsolete bridge is one that was built to standards obsolete bridge is one that was built to standards that do not meet the minimum federal clearance that do not meet the minimum federal clearance requirements for a new bridge. These bridges are requirements for a new bridge. These bridges are not automatically rated as structurally deficient, not automatically rated as structurally deficient, nor are they inherently unsafe. nor are they inherently unsafe.

Federal Funding EligibilityFederal Funding Eligibility

A bridge that is Structurally Deficient A bridge that is Structurally Deficient or Functionally Obsolete and has a or Functionally Obsolete and has a SR of SR of 8080 or less is eligible for federal or less is eligible for federal rehabilitationrehabilitation funding. funding.

A bridge that is Structurally Deficient A bridge that is Structurally Deficient (has a condition code of 4) or (has a condition code of 4) or Functionally Obsolete and has a SR Functionally Obsolete and has a SR of less than of less than 5050 is eligible for federal is eligible for federal replacementreplacement funding. funding.

Bridge CrewsBridge Crews

Emergency RepairsEmergency RepairsFlushingFlushingCrack SealingCrack SealingDeck SealingDeck SealingStructural RepairsStructural Repairs

Flushing the deck and railingFlushing the deck and railing

Cleaning the joints & Cleaning the joints & documenting leaking areasdocumenting leaking areas

Sealing Hairline CracksSealing Hairline Cracks

Sealing hairline crackswith epoxy penetrant sealer

Contract WorkContract WorkDeck OverlaysDeck OverlaysExpansion Joint ReplacementExpansion Joint ReplacementDeck ReplacementsDeck ReplacementsPaintingPaintingRailing Repair/ReplacementRailing Repair/Replacement

Deck Overlay

Deck Replacement

Painting

2007 Performance Summary 2007 Performance Summary for TH Bridge Structural for TH Bridge Structural Condition (20’ and overCondition (20’ and over))

Statewide average of bridges in Poor condition dropped from 3.6% to 3.1% reflecting a steady improvement in condition since 2003.

Bridges in Poor and Fair condition dropped slightly from 11.3 to 11.1%.

Statewide average bridges in “Good” structural condition moved above the 55% target to 55.2% this year as a result of the increased level of system expansion and bridge preservation investments that began in 2002.

0

2

4

6

8

10

12

14

16

18

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

% i

n Po

or C

ondi

tion STATEWIDESTATEWIDE

Trunk Highway Trunk Highway Principal Arterial Principal Arterial

BridgesBridges (Over 20’) (Over 20’)

Structural Condition Structural Condition Performance TargetPerformance Target

(Percentage by Area)(Percentage by Area)

50

55

60

65

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

% i

n G

ood C

ondit

ion

Poor Condition Target – 2%

Good Condition Target – 55%

January 2008

Principal Arterial = 85% of TH Bridge Area

Fair & Poor Condition Target – 16%

55.2%

11.1%

3.1%

Minnesota Deficient & Functionally Minnesota Deficient & Functionally Obsolete Bridges – how we Obsolete Bridges – how we

compare*compare* Interstate and State Bridges (20’ and over)Interstate and State Bridges (20’ and over)

– Total F.O. – 6% MN : 14.6% NationallyTotal F.O. – 6% MN : 14.6% Nationally– Total S.D. – 3% MN : 6.6% NationallyTotal S.D. – 3% MN : 6.6% Nationally

City/County/Township Bridges (20’ and City/County/Township Bridges (20’ and over)over)– Total F.O. – 3% MN : 11.6% NationallyTotal F.O. – 3% MN : 11.6% Nationally– Total S.D. – 11% MN : 14.9% NationallyTotal S.D. – 11% MN : 14.9% Nationally

* Source: “Better Bridges” Better Roads 2007 Bridge Inventory, November 2007; 42 * Source: “Better Bridges” Better Roads 2007 Bridge Inventory, November 2007; 42 states reporting.states reporting.

42

MN/DOT BRIDGE CONSTRUCTIONLet or Programmed

Includes Bridge Expansion, Replacement, Preservation, and Culverts January 4, 2008

ACTUAL BRIDGE & CULVERTS ESTIMATED BRIDGE & CULVERTS

Cost is for bridge portion of contract, does not include approach roadway cost. Yearly total is the sum of all bridge contract let that fiscal year. FY 2008 does not include I-35W Emergency Replacement Bridge Costs.

Fiscal Year

57.144.846.5

74.5 86.3

45.8 44.9

133.9

110.4 113.0

192.5

174.2

0

20

40

60

80

100

120

140

160

180

200

97 98 99 '00 '01 '02 03 04 05 06 07 08

DO

LL

AR

S I

N M

ILL

ION

S

43

MN/DOT BRIDGE CONSTRUCTIONLet or Programmed

Includes Bridge Replacement, Preservation and Culverts January 4, 2008

ACTUAL BRIDGE & CULVERTS ESTIMATED BRIDGE & CULVERTS

Cost is for bridge portion of contract, does not include approach roadway cost. Yearly total is the sum of all bridge contract let that fiscal year. FY 2008 does not include I-35W Emergency Replacement Bridge Costs.

30.426.132.2

52.6

25.927.336.5

91.3

75.3

40.3

132.0

103.1

0

20

40

60

80

100

120

140

160

180

200

97 98 99 '00 '01 '02 03 04 05 06 07 08

DO

LL

AR

S I

N M

ILL

ION

S

Fiscal Year

Long Term PlanningLong Term Planning

Planned Investments vs. Bridge Needs(2008-2028)

0

50

100

150

200

250

2019-20282012-20182008-2011STIP

Annual Bridge ProjectNeeds

in Millions(Including Inflation)

80

130+/-

60

Bridge Needs (STIP & 2012-2028 Model)

Planned Investments

01/31/08

Gap = 20M/yr

200+/-

Add’l Major Bridges:29

Add’l Major Bridges:98

Add’l Major Bridges:42

Targeting the Right TH Targeting the Right TH BridgesBridges

Goal is to Fund the Goal is to Fund the Replacement/Renovation in the Replacement/Renovation in the STIP years or 2012-2018 time STIP years or 2012-2018 time period of the current:period of the current:

3.1% Poor Condition (Structurally 3.1% Poor Condition (Structurally Deficient) &Deficient) &

8% Fair Condition Bridges8% Fair Condition Bridges

Fracture Critical BridgesFracture Critical Bridges

Fracture-criticalFracture-critical (FC)(FC) — — a fracture-a fracture-critical bridge typically has a steel critical bridge typically has a steel superstructure with load (tension) superstructure with load (tension) carrying members arranged in a carrying members arranged in a manner in which if one fails, the bridge manner in which if one fails, the bridge could collapse. Examples of fracture could collapse. Examples of fracture critical bridges are two girder bridges critical bridges are two girder bridges or truss bridges. The classification of or truss bridges. The classification of fracture critical fracture critical does notdoes not mean the mean the bridge is inherently unsafebridge is inherently unsafe

Fracture Critical Bridges, Fracture Critical Bridges, cont’dcont’d

Not all fracture critical bridges are planned for Not all fracture critical bridges are planned for replacement in the next 20 years. The right work replacement in the next 20 years. The right work planned for some FC bridges is painting, overlays planned for some FC bridges is painting, overlays and/or other repairs.and/or other repairs.

Three bridges are planned for replacement in the Three bridges are planned for replacement in the STIP years (2008-2012):STIP years (2008-2012):

- 2008 – TH 11 Bridge in Drayton, ND/Robin, MN- 2008 – TH 11 Bridge in Drayton, ND/Robin, MN

- 2009 – Bridge 5388 TH 24 in Meeker County- 2009 – Bridge 5388 TH 24 in Meeker County

- 2011 – TH 52 Lafayette Bridge in St. Paul- 2011 – TH 52 Lafayette Bridge in St. Paul Another 13 bridges are planned for replacement Another 13 bridges are planned for replacement

in 2012-2018.in 2012-2018.

DistrictDistrict BridgeBridge FYFY Bridge Cost in Bridge Cost in Construction FYConstruction FY

22 TH 11 /Red River at RobbinTH 11 /Red River at Robbin 20092009 14*14*

MM TH 52/Mississippi River – LafayetteTH 52/Mississippi River – Lafayette 20112011 130130

66 I-90/Mississippi River – DresbachI-90/Mississippi River – Dresbach 20142014 58*58*

66 TH 43/Mississippi River – WinonaTH 43/Mississippi River – Winona 20172017 9090

33 TH 23/Mississippi River – St CloudTH 23/Mississippi River – St Cloud 20152015 3838

MM TH 61/Mississippi River – HastingsTH 61/Mississippi River – Hastings 20172017 120120

MM TH 36/St Croix RiverTH 36/St Croix River 20242024 218*218*

TOTALTOTAL 668 Million668 Million

Statewide Bridge Preservation Statewide Bridge Preservation FundFund

2009-20242009-2024• Fund Large Bridge Preservation Projects Where Project Cost

Exceeds 50% of an ATP’s Annual Federal Funds.

• 100% of Bridge Costs Eligible for Funding (does not include grading, R/W)

• Fund is Capitalized with up to $80 Million Annual in Fiscal 2009-2024

* Mn/DOT Share of Border Bridge

Mn/DOT BridgesMn/DOT Bridges Legislative Staff Briefing Legislative Staff Briefing

February 5, 2008February 5, 2008

Questions?

Contact Information:

Dan Dorgan, State Bridge Engineer

Phone: (651) 366-4501, email:dan.dorgan@dot.state.mn.us

Nancy Daubenberger, Bridge Planning Engineer

Phone: (651) 366-4504, email:nancy.daubenberger@dot.state.mn.us