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1 Mn/DOT Bridges Legislative Staff Briefing Bridge Design and Bridge Types Bridge Design and Bridge Types Bridge Inspection Program Bridge Inspection Program.

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Presentation on theme: "1 Mn/DOT Bridges Legislative Staff Briefing Bridge Design and Bridge Types Bridge Design and Bridge Types Bridge Inspection Program Bridge Inspection Program."— Presentation transcript:

1 1 Mn/DOT Bridges Legislative Staff Briefing Bridge Design and Bridge Types Bridge Design and Bridge Types Bridge Inspection Program Bridge Inspection Program Bridge Terminology Bridge Terminology Bridge Crews and Contract Work Bridge Crews and Contract Work Current Bridge Structural Condition and Trends Current Bridge Structural Condition and Trends Bridge Preservation Investments Bridge Preservation Investments February 5, 2008

2 Bridges Are Designed According to a National Code American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specification is the governing code. American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specification is the governing code. All 50 states participate in code development and annual updating. All 50 states participate in code development and annual updating. Development of the first national bridge design code began in the 1920s and was published in Development of the first national bridge design code began in the 1920s and was published in Reflects the combined experience of 50 states. Reflects the combined experience of 50 states.

3 Concrete Box Culverts

4 Concrete

5 Steel Beams

6 Concrete slab for shorter spans. Concrete slab for shorter spans. Prestressed beams for intermediate spans with straight alignment. Prestressed beams for intermediate spans with straight alignment. Steel beams for intermediate/long spans or curved alignment. Steel beams for intermediate/long spans or curved alignment.

7 Steel or concrete box girders for major spans. Steel or concrete box girders for major spans. Other types for very long spans and signature bridges. Other types for very long spans and signature bridges. –Arch –Suspension –Cable-stayed –Extradosed

8 Safety Factors in Bridge Design Bridges are intentionally over-designed to provide a safety factor for many issues including the following: With a year service life, traffic may increase in frequency or weight. With a year service life, traffic may increase in frequency or weight. Materials may have slight imperfections from specifications Materials may have slight imperfections from specifications Tolerances in construction or fabrication may cause a bridge component to be slightly different than designed. Tolerances in construction or fabrication may cause a bridge component to be slightly different than designed. Steel will corrode during the bridge lifetime and loose some thickness Steel will corrode during the bridge lifetime and loose some thickness Deterioration of concrete, steel, timber Deterioration of concrete, steel, timber

9 Who Designs TH Bridges? Mn/DOT Bridge Office (in Oakdale) has a preliminary design unit, hydraulic unit, cost estimating unit and five final design units to design bridges across the state. Mn/DOT Bridge Office (in Oakdale) has a preliminary design unit, hydraulic unit, cost estimating unit and five final design units to design bridges across the state. In-house, Mn/DOT is staffed to design for about $40 M-$50 M bridge program/year. In-house, Mn/DOT is staffed to design for about $40 M-$50 M bridge program/year. Program above this annual amount is sent out to consultants. Program above this annual amount is sent out to consultants.

10 Inspections

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13 Bridge Inspections, general Bridge Inspection Cycles – Bridges are inspected once every two years per National bridge Inventory System. In Minnesota, if the condition of the deck, superstructure or substructure is rated 4 or less, bridges are inspected annually. Bridge Inspection Cycles – Bridges are inspected once every two years per National bridge Inventory System. In Minnesota, if the condition of the deck, superstructure or substructure is rated 4 or less, bridges are inspected annually. Fracture critical bridges get an in-depth inspection at least once every two years. Fracture critical bridges get an in-depth inspection at least once every two years. Mn/DOT Bridge Inspectors – Mn/DOT has 75 certified inspection team leaders. These inspection team leaders have taken three weeks of FHWA approved Bridge Inspector training. Mn/DOT Bridge Inspectors – Mn/DOT has 75 certified inspection team leaders. These inspection team leaders have taken three weeks of FHWA approved Bridge Inspector training.

14 Bridge Inspections, contd Equipment used for inspection - inspection equipment can include snooper trucks, aerial manlifts, ladders, measuring devices and various tools. Equipment used for inspection - inspection equipment can include snooper trucks, aerial manlifts, ladders, measuring devices and various tools. In-depth inspections use ultrasonic testing, die penetrant, and magnetic particle test methods and a video scope in order to detect cracks and/or corrosion. In-depth inspections use ultrasonic testing, die penetrant, and magnetic particle test methods and a video scope in order to detect cracks and/or corrosion. Critical Deficiency – any condition discovered during a scheduled bridge inspection that threatens public safety and, if not promptly corrected, could result in collapse or partial collapse of the structure. When inspectors report critical findings, immediate actions are taken to further assess the situation and to repair or close the bridge. Critical Deficiency – any condition discovered during a scheduled bridge inspection that threatens public safety and, if not promptly corrected, could result in collapse or partial collapse of the structure. When inspectors report critical findings, immediate actions are taken to further assess the situation and to repair or close the bridge.

15 What Are Inspectors Looking 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 that is causing distortion in a joint Assess condition of paint systems Assess condition of paint systems Distortion of members such as bowing not aligned as originally built Distortion of members such as bowing not aligned as originally built Scour from water flow around foundations Scour from water flow around foundations Leaking joints Leaking joints Support piers that are tilting or moving Support piers that are tilting or moving

16 Example of spalled concrete

17 Example of corroded steel girder

18 Example of tilting pier

19 Governors Inspection Program TH System: 3,875 Routine and FC Inspections 270 By Consultants Local System 141 FC inspections 43 By Consultants As of December 20 th all State Bridge inspections are up to date.

20 Bridge Terminology Condition rating – overall assessment of the physical condition of the deck, superstructure or substructure, range from 0 to 9. Condition rating – overall assessment of the physical condition of the deck, superstructure or substructure, range from 0 to 9. Sufficiency rating (SR) Sufficiency rating is a computed numerical value that is used to determine eligibility of a bridge for Federal funding. The sufficiency rating formula result varies from 0 to 100. The formula includes factors for structural condition rating, bridge geometry, and traffic considerations. Sufficiency rating (SR) Sufficiency rating is a computed numerical value that is used to determine eligibility of a bridge for Federal funding. The sufficiency rating formula result varies from 0 to 100. The formula includes factors for structural condition rating, bridge geometry, and traffic considerations.

21 National Bridge Inventory Condition Ratings 9 – Excellent 9 – Excellent 8 – Very Good 8 – Very Good 7 – Good - No problems noted. 7 – Good - No problems noted. 6 – Satisfactory – Some minor problems. 6 – Satisfactory – Some minor problems. 5 – Fair – All primary structural elements are sound but may have minor section loss, cracking, spalling, or scour. 5 – Fair – All primary structural elements are sound but may have minor section loss, cracking, spalling, or scour.

22 National Bridge Inventory Condition Ratings, contd 4 – Poor – Advanced section loss, deterioration, spalling or scour. 4 – Poor – Advanced section loss, deterioration, spalling or scour. 3 – Serious – Loss of section, deterioration, spalling or scour have seriously affected the primary structural components. 3 – Serious – Loss of section, deterioration, spalling or scour have seriously affected the primary structural components. 2 – Critical – Advanced deterioration of primary structural elements. 2 – Critical – Advanced deterioration of primary structural elements. 1 – Imminent Failure – Major deterioration or section loss in critical structural components. Bridge is closed to traffic, but corrective action may put it back in light service. 1 – Imminent Failure – Major deterioration or section loss in critical structural components. Bridge is closed to traffic, but corrective action may put it back in light service. 0 – Failed – Out of service, beyond corrective action. 0 – Failed – Out of service, beyond corrective action.

23 Summary of Sufficiency Rating (SR) Factors 1. Structural Adequacy & Safety (55% max) 2. Serviceability & Functional Obsolescence (30% max) 3. Essentiality for Public Use (15% max)

24 Summary of Sufficiency Rating (SR) Factors 1. Structural Adequacy & Safety (55% max) – includes superstructure, substructure, culverts, and inventory rating. 1. Structural Adequacy & Safety (55% max) – includes superstructure, substructure, culverts, and inventory rating. 2. Serviceability & Functional Obsolescense (30% max) – includes number of lanes on the structure, Average Daily Traffic (ADT), approach roadway width, structure type, bridge roadway width, vertical clearance over deck, deck condition, structural evaluation, deck geometry, under- clearances, waterway adequacy, approach roadway alignment, STRAHNET highway designation. 2. Serviceability & Functional Obsolescense (30% max) – includes number of lanes on the structure, Average Daily Traffic (ADT), approach roadway width, structure type, bridge roadway width, vertical clearance over deck, deck condition, structural evaluation, deck geometry, under- clearances, waterway adequacy, approach roadway alignment, STRAHNET highway designation. 3. Essentiality for Public Use (15% max) – includes detour length, ADT, and STRAHNET highway designation. 3. Essentiality for Public Use (15% max) – includes detour length, ADT, and STRAHNET highway designation.

25 Bridge Terminology, contd Structurally deficient (SD) Bridges are classified as structurally deficient if they have a general condition rating for the deck, superstructure, substructure or culvert as 4 or less or if the road approaches regularly overtop due to flooding. The fact that a bridge is structurally deficient does not imply that it is unsafe. Structurally deficient (SD) Bridges are classified as structurally deficient if they have a general condition rating for the deck, superstructure, substructure or culvert as 4 or less or if the road approaches regularly overtop due to flooding. The fact that a bridge is structurally deficient does not imply that it is unsafe. Functionally obsolete (FO) a functionally obsolete bridge is one that was built to standards that do not meet the minimum federal clearance requirements for a new bridge. These bridges are not automatically rated as structurally deficient, nor are they inherently unsafe. Functionally obsolete (FO) a functionally obsolete bridge is one that was built to standards that do not meet the minimum federal clearance requirements for a new bridge. These bridges are not automatically rated as structurally deficient, nor are they inherently unsafe.

26 Federal Funding Eligibility A bridge that is Structurally Deficient or Functionally Obsolete and has a SR of 80 or less is eligible for federal rehabilitation funding. A bridge that is Structurally Deficient or Functionally Obsolete and has a SR of 80 or less is eligible for federal rehabilitation funding. A bridge that is Structurally Deficient (has a condition code of 4) or Functionally Obsolete and has a SR of less than 50 is eligible for federal replacement funding. A bridge that is Structurally Deficient (has a condition code of 4) or Functionally Obsolete and has a SR of less than 50 is eligible for federal replacement funding.

27 Bridge Crews Emergency Repairs Flushing Crack Sealing Deck Sealing Structural Repairs

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29 Flushing the deck and railing

30 Water leakage, hairline cracks resulting from pack rust

31 Cleaning the joints & documenting leaking areas

32 Sealing Hairline Cracks Sealing hairline cracks with epoxy penetrant sealer

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34 Contract Work Deck Overlays Expansion Joint Replacement Deck Replacements Painting Railing Repair/Replacement

35 Deck Overlay

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37 Deck Replacement

38 Painting

39 2007 Performance Summary for TH Bridge Structural Condition (20 and over) Statewide average of bridges in Poor condition dropped from 3.6% to 3.1% reflecting a steady improvement in condition since 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.

40 STATEWIDE Trunk Highway Principal Arterial Bridges (Over 20) Structural Condition Performance Target (Percentage by Area) 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%

41 Minnesota Deficient & Functionally Obsolete Bridges – how we compare* Interstate and State Bridges (20 and over) Interstate and State Bridges (20 and over) –Total F.O. – 6% MN : 14.6% Nationally –Total S.D. – 3% MN : 6.6% Nationally City/County/Township Bridges (20 and over) City/County/Township Bridges (20 and over) –Total F.O. – 3% MN : 11.6% Nationally –Total S.D. – 11% MN : 14.9% Nationally * Source: Better Bridges Better Roads 2007 Bridge Inventory, November 2007; 42 states reporting.

42 42 MN/DOT BRIDGE CONSTRUCTION L et 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 '00'01' DOLLARS IN MILLIONS

43 43 MN/DOT BRIDGE CONSTRUCTION L et 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. Fiscal Year

44 Long Term Planning

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46 Planned Investments vs. Bridge Needs ( ) STIP Annual Bridge Project Needs in Millions (Including Inflation) /- 60 Bridge Needs (STIP & Model) Planned Investments 01/31/08 Gap = 20M/yr 200+/- Addl Major Bridges: 29 Addl Major Bridges: 98 Addl Major Bridges: 42

47 Targeting the Right TH Bridges Goal is to Fund the Replacement/Renovation in the STIP years or time period of the current: 3.1% Poor Condition (Structurally Deficient) & 8% Fair Condition Bridges

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

49 Fracture Critical Bridges, contd Not all fracture critical bridges are planned for replacement in the next 20 years. The right work planned for some FC bridges is painting, overlays and/or other repairs. Not all fracture critical bridges are planned for replacement in the next 20 years. The right work planned for some FC bridges is painting, overlays and/or other repairs. Three bridges are planned for replacement in the STIP years ( ): Three bridges are planned for replacement in the STIP years ( ): – TH 11 Bridge in Drayton, ND/Robin, MN – Bridge 5388 TH 24 in Meeker County – TH 52 Lafayette Bridge in St. Paul Another 13 bridges are planned for replacement in Another 13 bridges are planned for replacement in

50 DistrictBridgeFY Bridge Cost in Construction FY 2 TH 11 /Red River at Robbin * M TH 52/Mississippi River – Lafayette I-90/Mississippi River – Dresbach * 6 TH 43/Mississippi River – Winona TH 23/Mississippi River – St Cloud M TH 61/Mississippi River – Hastings M TH 36/St Croix River * TOTAL 668 Million Statewide Bridge Preservation Fund Fund Large Bridge Preservation Projects Where Project Cost Exceeds 50% of an ATPs 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 * Mn/DOT Share of Border Bridge

51 Mn/DOT Bridges Legislative Staff Briefing February 5, 2008 Questions? Contact Information: Dan Dorgan, State Bridge Engineer Phone: (651) , Nancy Daubenberger, Bridge Planning Engineer Phone: (651) ,


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