|
Policy and Procedure Manual: Fracture Critical Bridge Inspection Policy for Local Units of Government
Table of Contents
PREFACE
The Fracture Critical Inspection Policy and Practice Manual was developed as a team effort with local interest and concerns in mind.
It is intended to be a practical manual to provide assistance and guidance in the inspection and development of Fracture Critical Bridge Inspection Report.
Members of the team were:
- Francis Bennett - Assistant Bridge Maintenance Engineer, Wis DOT District #7, Rhinelander, WI
- Daniel J. Fedderly - Highway Commissioner, St. Croix County, Hammond, WI
- Philip Fish - Specialized Bridge Inspection, Wis DOT Central Office, Madison, WI
- David Lambert - County Engineer, Grant County, Lancaster, WI
- Matthew Murphy - Assistant Bridge Maintenance Engineer, Wis DOT District #1, Madison, WI
- Thomas H. Rohrer - Bridge Maintenance Engineer, Wis DOT District #6, Eau Claire, WI
- Steve Schofield - Certified Bridge Inspector, St. Croix County, Hammond, WI
SECTION 1.0 INTRODUCTION
1.1 Purpose
To ensure a safe transportation system for all who travel on highways in Wisconsin, and to comply with Federal Regulations 23 CFR 650.303(e)(1), a comprehensive Fracture Critical Bridge Inspection procedure has been developed by Wisconsin Department of Transportation and Wisconsin County Highway Association.
Wisconsin Administrative Code, Chapter Trans 212, "Standards For The Inspection Of Bridges In Wisconsin" shall apply.
The purpose of this policy and procedure manual is to serve as standard and to provide uniformity in the procedures and policies for determining the physical condition, reporting maintenance needs and to identify bridges that require load rating capacity for Fracture Critical Bridges in Wisconsin.
1.2 Scope
This procedure and practice manual was developed with priority given to the safety of bridges, practical inspection procedures, and the safety of the inspector. It was developed to assist bridge owners by establishing inspection procedures that meet the requirements of the National Bridge Inspection Standards (NBIS). The manual has been divided into six sections, with each section representing a distinct phase of the overall Fracture Critical Inspection Procedure.
SECTION 1 contains introductory information and background information on the Inspection of Fracture Critical Bridges along with specifications used to develop this policy and procedures manual.
SECTION 2 contains the qualification and responsibility requirements for the Inspection Program Manager and Inspection Team Leader.
SECTION 3 explains critical steps in inspection preparation; plan review, identification of fracture critical members, and developing an inspection plan.
SECTION 4 contains information on personal safety and public safety while performing Fracture Critical Bridge Inspections.
SECTION 5 includes procedures for field inspection to be used to perform Fracture Critical Inspections, Inspection Report Forms and Attachment Report Forms where additional information is required to explain the bridge inspection.
SECTION 6 is an appendix which is intended to be an inspectors guide while performing Fracture Critical Inspections. It includes examples of Fracture Critical Bridges, Bending and Stress Diagrams, Fracture Critical Components, Typical Pin & Hanger Parts, Typical Pin Parts, Typical Crack Locations, and a completed Fracture Critical Inspection Report.
1.3 Applicability
The provisions of this policy and procedure manual apply to all highway structures which qualify as Fracture Critical Bridges in accordance with the National Bridge Inspection Standards (NBIS).
1.5 Definitions
AASHTO: American Association of State Highway and Transportation Officials.
Bridge Owner: An organization or agency responsible for the inspection, maintenance and load rating of highway bridges.
Condition Rating: The result of the determination of functional capacity and the physical condition of bridge components including the extent of deterioration and other defects.
FHWA: Federal Highway Administration, U.S. Department of Transportation.
Fracture Critical Bridge: It is a bridge that contains fracture critical members or members components (FCMs) are tension members or tension components of members whose failure would be expected to result in collapse of the bridge.
"Hands-On" Inspection: Visual/Manual Inspection from a distance no greater than arm's length of the member and/or member component.
Load Rating: The determination of the live load carrying capacity of an existing bridge using existing bridge plans supplemented by information gathered from the field inspection.
MUTCD: The FHWA Manual of Uniform Traffic Control Devices.
National Bridge Inspection Standards (NBIS): Federal regulations establishing requirements for inspection procedures, frequency of inspections, qualifications of personnel, inspection reports, and preparation and maintenance of bridge inventory records. The NBIS apply to all structures defined as bridges located on or over all public roads.
Quality Control: Procedures that are intended to maintain the quality of a bridge inspection at or above the specified level.
Quality Assurance: The use of sampling to verify or measure the level of the entire bridge inspection program.
1.6 Important References
- AASHTO Standard Specifications for Highway Bridges, Washington, D.C. 1989, with annual interim updated specifications.
- AASHTO Manual for Condition Evaluation of Bridges, Washington, D.C. 1994.
- AASHTO Guide Specifications for Strength Evaluation of Existing Steel and Concrete Bridges, Washington, D.C. 1989.
- AASHTO Guide Specifications for Fatigue Evaluation of Existing Steel Bridges, Washington, D.C. 1990.
- AASHTO Guide Specifications for Strength Design of Truss Bridges (Load Factor Design), Washington, D.C. 1985.
- AASHTO Guide Specifications for Fatigue Design of Steel Bridges, Washington, D.C. 1989.
- AASHTO Guide Specifications for Fracture Critical Non-Redundant Steel Bridge Members, Washington, D.C. 1986.
- AASHTO Standard Specifications for Movable Highway Bridges, Washington, D.C. 1988.
- FHWA Inspection of Fracture Critical Bridge Members, Washington, D.C. 1986.
- FHWA Bridge Inspector's Training Manual 90, Washington, D.C. 1990.
- FHWA Bridge Inspector's Manual for Movable Bridges, Washington, D.C. 1977.
- FHWA Non-Destructive Testing Methods for Steel Bridges, Washington, D.C. 1986.
- FHWA Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges, Washington, D.C. 1988.
- FHWA Technical Advisory - Revisions to the National Bridge Inspection Standards (NBIS), T5140.21, Washington, D.C. Sept. 1988.
- FHWA Manual of Uniform Traffic Control Devices, Washington, D.C. 1988.
- U.S. Government, National Bridge Inspection Standards, Code of Federal Regulations, Title 23, Part 650, Subpart C, Oct. 1988.
- Wisconsin Department of Transportation, Maintenance Manual, Madison WI. Jan. 1991.
- Wisconsin Department of Transportation, Standard Specifications for Road and Bridge Construction, Madison WI, Latest Edition.
SECTION 2.0 QUALIFICATIONS AND RESPONSIBILITIES
2.1 General
Qualified personnel shall be utilized in conducting Fracture Critical Bridge Inspections. Minimum qualifications for the levels of responsibility are described below. For purpose of the policy and procedure manual and in accordance with TRANS 212, the Inspection Program Manager shall be the County Highway Commissioner or their delegate.
2.2 Inspection Team
The Inspection Team shall consist of the Inspection Program Manager, the Inspection Team Leader (Inspector) and all individual assistants as required and designated by the Inspection Program Manager.
2.3 Inspection Program Manager
The National Bridge Inspection Standards, in conjunction with Wisconsin Department of Transportation policy, provide minimum qualifications for two levels of responsibility. The first, or senior, level is the individual in charge of the organizational unit. A unit leader should:
- Be a registered professional engineer and have passed a required two week comprehensive training course on "Bridge Inspectors Training Manual 90"
or
- Be qualified for registration as a professional engineer under the laws of the state and have passed a required two week comprehensive training course on "Bridge Inspectors Training Manual 90"
or
- Have a minimum of 10 years experience in bridge inspection assignments in a responsible capacity and have passed a required two week comprehensive training course on "Bridge Inspectors Training Manual 90."
2.4 Inspection Team Leader (Inspector)
The second level of responsibility described in the standards is the Inspection Team Leader who is in charge of the Bridge Inspection Team at the bridge site. The qualifications of a Team Leader are:
- Have the qualifications specified for the Program Manager
or
- Have a minimum of 5 years of experience in bridge inspection assignments in a responsible capacity and have passed a required two week comprehensive training course on "Bridge Inspectors Training Manual 90."
2.5 Quality Measures
In order to maintain accuracy and consistency of the Fracture Critical Bridge Inspection program, the following Quality Measures are required.
2.5.1 Wisconsin Department of Transportation
The Wisconsin Department of Transportation Bridge Maintenance Engineer and District Bridge Maintenance Engineers shall provide training to ensure consistency and accuracy in the program on a statewide basis.
2.5.2 Inspection Program Manager
All Fracture Critical Bridge Inspection Reports shall be reviewed, signed, and dated by the Inspection Program Manager or assigned delegate (person other than Team Leader).
The Inspection Program Manager shall review Fracture Critical Bridge Inspection report recommendations with Inspection Team Leader and bridge owners to develop a maintenance "Plan-of-Action" to assure inspection recommendations are acted on.
The Inspection Program Manager shall maintain a "Master List" of bridges containing:
- Fracture Critical Members or Member Components.
- Inspection Interval or Interim Inspection Interval.
- Status of "Plan-of-Action" recommendations.
The Inspection Program Manager shall perform a periodic field review of inspection teams to assure consistent inspection procedures and quality.
2.5.3 Inspection Team Leader
All Fracture Critical Bridge Inspection Reports shall be signed and dated by the Inspection Team Leader.
The Inspection Team leader shall perform periodic reviews with bridge owner of maintenance "Plan-of-Action" to assure that inspection recommendations are performed. All deficiencies identified by the inspection shall be reported to the Inspection Program Manager.
SECTION 3.0 INSPECTION PREPARATION
3.1 General
The inspection team should develop the Inspection Plan. Inspection preparation is an important part of the Fracture Critical Bridge Inspection. Important steps that will help in accomplishing a successful inspection are; Planning, Scheduling, Equipment, Personnel Requirements, and Field Inspection Procedures.
3.2 Inspection Interval
Fracture Critical Bridge Inspections shall be at regular intervals not to exceed seventy two (72) months or more frequently, as approved by the Inspection Program Manager (County Highway Commissioner or their delegate). This inspection may be a supplemental inspection to the routine (Trans 212) inspection.
3.3 Interim Inspection Interval
Interim inspections shall consist of the fracture critical members and/or member components determined to be deficient and in need of more frequent inspections. These shall be determined at the discretion and recommended frequency of the Inspection Program Manager.
3.4 Historical and Plan Review
It is critical to gather all of the historical information that is available. Suggested information that may be available:
- Original Design Plans
- "As-Built" Plans
- Original Shop Drawings
- Construction History
- Maintenance History
- Rehabilitation History
- Bridge Inspection Reports and Photographs
This information should be reviewed by the Inspection Program Manager and Inspection Team Leader prior to performing the Fracture Critical Inspection in order to determine the Fracture Critical Members or Member Components. It is strongly recommended that original plans and documents remain in the office of the maintaining agency and that only copies be taken to the field.
3.5 Identification of Fracture Critical Members (FCMs)
FCMs and Tension Members shall be identified by the Program Manager working with the Inspection Team Leader. This identification shall be shown on the plans or a sketch of the bridge.
FCMs, Member Components, and all other Tension Members must be identified on the Inspection form or an attached plan. (Examples shown Appendix Section 6.)
To qualify as a FCM, the member or components of the member must be in tension and there must NOT be any other member or system of members which will serve the functions of the member in question should it fail. The alternate systems or members represent redundancy.
Tension components of a bridge member consist of components of tension members and those portions of a flexural member that are subject to tension stress. Any attachment having a length in the direction of the tension stress greater than 4 inches (10 cm) that is welded to the tension area of a component of a "Fracture Critical" member shall be considered part of the tension component and, therefore shall be considered "Fracture Critical."
FCMs have all or part of their cross section in tension. Most cracks in steel members occur in the tension zones, generally at a flaw or defect in the base material. Frequently the crack is a result of fatigue occurring near a weld, a material flaw and/or changes in member cross section.
After the crack occurs, failure of the member could be sudden and lead to collapse of the bridge. For this reason steel bridges with the following structural characteristics or components should be reviewed for a Fracture Critical Inspection.
- Overhead Two-Truss Bridges
- Low Two-Truss Bridges
- Deck Two-Truss Bridges
- Thru Girder Bridges
- Two Girder Bridges
- Tied Arch Bridges
- Movable Bridges
- Steel Pier Caps and Cross Girders
- Pin and Hanger System on 2 or 3 Girder Systems
See Appendix Section 6, for examples of Fractures Critical Bridges, Components, Bending Definitions, Typical Crack Locations, and Typical Pin & Hanger Parts.
3.6 Inspection Plan
The inspection plan is the final step in preparation for the field inspection. From the information gathered, a plan needs to be organized for the field inspection. A pre-inspection visit to the site may be required to finalize the Inspection Plan.
Visual inspection is intended to be the primary inspection method of this policy. This policy requires that each Fracture Critical Member or Member Component be inspected "hands-on"* a maximum distance of one arm's length for the entire length of the member and/or member component.
An inspection plan may include some or all of the following and must be prepared prior to the field inspection:
- A brief historical fact statement
- Essential plans that would help with field inspection
- Identification of Fracture Critical Members and/or Member Components along with tension members on inspection form or attached plan.
- Access equipment and personnel needed to perform the field inspection
- Inspection tools and safety equipment needed to perform the field inspection
- Traffic Control requirements
- Estimate of inspection time
- Coordination and notification of owner and other agencies.
To meet the minimum requirements of this policy, all of the required information shall be noted in appropriate locations of the Fracture Critical Bridge Inspection Report Form. On larger or more complex structures, it may be necessary to create separate chapters for each of the required areas of the Inspection Plan, which can be attached to the Fracture Critical Bridge Inspection Report Form.
SECTION 4.0 SAFETY
4.1 General
Safety of both the inspection team members and the public is paramount. Bridge owners or their delegated inspection authority should develop a safety program to provide inspection personnel with information concerning their safety and health including the proper operation of inspection tools and equipment. The program should embody applicable Federal, State, and Local legislation governing safety and health in the bridge inspection work environment.
4.2 Public Safety
In the interest of public safety, bridge owners or their delegated inspection authority should employ proper procedures for traffic control and work zone protection during the inspection of the bridge. The MUTCD as supplemented by Wisconsin DOT should be used as a guide for such procedures.
4.3 Personnel Safety
Personal protective clothing should be worn at all times including hard hats, vests, safety glasses (where needed), appropriate footwear, climbing lanyards and floatation devices (where needed). Proper hearing, sight, respiratory and face protection methods should be practiced whenever using manual or power tools. All equipment, safety devices, and machinery should be kept in the best possible operating condition.
Inspection vehicles, aerial lifts, and other access equipment should be operated in accordance with the operating manuals provided by the manufacturer. Personnel should be trained in safe use of the equipment and emergency procedures in event of malfunction.
Belts, lanyards, harnesses, flotation devices and other personal safety equipment should be used in accordance with applicable standards. All lifelines, belts, lanyards, and floatation equipment should be maintained in good repair. Worn or damaged equipment should be repaired or replaced.
Proper safety precautions should be employed when entering confined spaces, such as the interior of a box girder. Air testing, air changes and/or the use of air packs may be required.
Inspection personnel should be trained in proper safety precautions when working on bridges with lead paint. Lead paint is classified as a hazardous material and is harmful to persons not taking proper precautions.
Inspection personnel should have first aid training.
Safety programs provide a guide to inspection personnel but do not substitute for good judgement and common sense. It should be recognized that each bridge site is unique. In situations where unusual working conditions exist, specialized safety precautions may be required.
SECTION 5.0 FIELD INSPECTION PROCEDURES, REPORTS AND CONDITION RATINGS
5.1 General
Field inspection procedures are the implementation of an inspection plan. Good preparation will increase the quality of the field inspection and ensure that all needed tools, safety devices and operational procedures are available to effectively and efficiently complete the task. It is critical that the Inspection Team Leader guide the field inspection process to assure that each inspection emphasizes obtaining the desired level of quality and assures public safety.
5.2 Field Inspection Procedures
5.2.1 History Review
The construction history along with any rehabilitation history and maintenance history should be reviewed at the bridge site prior to performing an inspection. This will be helpful in possibly defining deficiencies that may be found during the inspection. It also is advantageous to know the age of possible deficiencies to determine their criticality when making final recommendations.
5.2.2 Fracture Critical Member, Tension Member Plan Review
Bridge orientation should be evaluated to determine the location of Fracture Critical Members and Tension Members. Location of panel points in relation to orientation of the bridge should be determined.
The Fracture Critical Members and Tension Members that have been identified on the Inspection Plan, should be reviewed prior to performing the inspection. Discussion should take place as to the type of deficiencies that may be expected from the details shown for the bridge and if any of the repairs or rehabilitation that has occurred since original construction could have influenced the deterioration of a particular member or connection. Possible locations for potential cracking should be identified and highlighted on the inspection plan.
5.2.3 Traffic Control
Traffic Control Requirements should be reviewed prior to performing an inspection to assure safety of the Inspection Team and the traveling public. The Inspection Team should review the traffic control requirements with persons performing the traffic control, if they are not part of the inspection team. The traffic control requirements shall be documented on the Fracture Critical Bridge Inspection Report Form. Any unsafe traffic control conditions should be corrected before performing an inspection.
5.2.4 Access Equipment and Procedures
Access equipment must be evaluated to determine if it can provide the required visual "hands-on" inspection of all Fracture Critical Members and/or Components.
Typical methods of access are available but not limited to:
- Under Bridge Inspection Units
- Aerial Lifts
- Scaffolding and Staging
- Boats
- Ladders
- Climbing
Access equipment and procedures need to be evaluated for personal safety prior to inspection. The safety sheet provided with the equipment, including emergency evacuation procedures should be reviewed.
5.2.5 Personal Safety
All personal safety equipment needed for an inspection shall be identified and checked for condition. Such equipment may include but not be limited to: high visibility clothing, body harnesses, hard hat, safety shoes, eye protection, ear protection, respiratory protection, and protection from hazardous paint or other materials.
Safety of the inspector is essential in providing a quality Fracture Critical Inspection. Provision for all the proposed safety requirements is paramount to providing the necessary confidence for the inspector, to ensure a quality fracture critical inspection.
5.2.6 Inspection Tools
A review of the tools listed on the inspection plan should be done along with a review of conditions on the bridge to determine what tools may be required to perform a thorough visual "hands-on" inspection.
There may a considerable amount of debris or corrosion in the areas that require inspection. It is critical that all debris and loose corrosion be removed to perform the inspection.
Inspection tools that may be helpful for an inspection include:
- Hand Scraper
- Geological Chipping Hammer
- Wire Brush
- Drafting Brush
- Pocket Knife
- Rulers
- Flash Light or Halogen Light if power is available
- 10 Power Magnifying Glass or Crack Comparator
- Camera
For difficult areas, small power grinders, wire brushes, or end grinders may be helpful.
5.2.7 Field Inspection
All Fracture Critical Members and/or Components identified on the Inspection plan must be inspected "hands-on". They shall be cleaned so that all extraneous material is removed to provide for a thorough evaluation.
The condition of each member and/or component must be determined including any deficiencies such as section loss, cracks, unspecified welds, field welds, tack welds, sharp bends or kinks, or other unspecified damage. See Appendix for examples.
Each member and/or component shall have its condition recorded on the Fracture Critical Bridge Inspection Form. If no deficiencies are noted, an ok must be recorded.
Additional information should be recorded for serious deficiencies and placed on attachment inspection forms. Such information may be sketches and photographs. The description of such deficiencies should include exact location and detailed dimensions which could help in determining the overall condition rating of the bridge.
Deficiencies that require emergency repairs or action shall be reported to the Inspection Program Manager and bridge owner immediately. If the Inspection Team Leader has doubt about the load carrying capacity of a bridge when such deficiencies are found, they shall take action to close the bridge to ensure safety to the public and make immediate contact with the Inspection Program Manager. Only the Program Manager (County Commissioner or their delegate) shall have the authority to reopen a bridge.
Section 5.3 Inspection Report Form and Attachments
 Click HERE to see Inspection Report Form.
 Click HERE to see Fracture Critical Bridge Inspection Report.
 Click HERE to see Fractural Critical Bridge Inspection Report.
SECTION 6.0 APPENDIX
6.1 Examples of Fracture Critical Bridges
- Truss Members
- Through Howe Truss
- Through Warren Truss
- Through Wipple Truss
- Through Baltimore Truss
- Through Pratt Truss
- Quadrangular Through Warren Truss
- Camel Back Truss
- K-Truss
- Through Truss
- Pony Truss
- Deck Truss
6.2 Bending and Stress Definitions
6.3 Examples of Fracture Critical Components
- Bending in Truss
- Bending in Girders
- Tension Stress - Cracks being pulled open by tensile forces.
6.4 Typical Pin Parts and Pin and Hanger Parts
6.5 Typical Crack Locations
6.6 Sample Fracture Critical Bridge Inspection
6.7 Sample Fracture Critical Bridge Member Identification Diagram
- Sample Bridge Inspection Report: Fracture Critical Bridge Inspection Report
6.8 Specialized Services
The Wisconsin Department of Transportation can offer specialized services which may be required on certain bridges for access or conditions found during inspection. These services may be used upon mutual agreement between the Program Manager and the appropriate Wisconsin DOT office. The cost of the services will be the actual cost of personnel and equipment utilized.
6.8.1 Access Equipment
The following equipment is available but not limited to:
- Under bridge Inspection Units
6.8.2 Specialized Inspection Methods
The following nondestructive inspection methods are available but not limited to:
- Ultrasound for analysis of pins, welds and cracks
- Dye penetrant for surface flaw analysis
- Magnetic particle for surface flaw analysis
- Ultrasound thickness gauge for section loss analysis
For further information, please contact Phil Fish, former Senior Bridge Inspection Engineer and NDE Manager, Wisconsin Department of Transportation
|
