FLH Bridge Inspection Manual_Current_20211227.pdf

FLH Bridge Inspection Manual Table of Contents

December 2021 i

Federal Lands Highway Bridge Inspection Program Manual

TABLE OF CONTENTS

CHAPTER 1 : INTRODUCTION ........................................................................................... 1-1

CHAPTER 2 : INSPECTION PROGRAM REQUIREMENTS ................................................ 2-1

2.1 Bridge Inspection Organization .............................................................................................................. 2-1

2.2 Responsibilities and Qualifications of Personnel .................................................................................... 2-1

2.3 Bridge Inspection Inventory ................................................................................................................... 2-3

2.4 Inspection Types and Frequencies .......................................................................................................... 2-3

CHAPTER 3 : INSPECTION PROCEDURES ....................................................................... 3-8

3.1 Preparation for Inspection ..................................................................................................................... 3-8

3.2 Field Inspection Equipment .................................................................................................................... 3-8

3.3 Safety Practices ...................................................................................................................................... 3-9

3.4 Field Documentation ............................................................................................................................ 3-10

3.5 Critical Finding ..................................................................................................................................... 3-11

3.6 Post-Inspection De-Briefing .................................................................................................................. 3-14

CHAPTER 4 : LOAD RATING AND POSTING ..................................................................... 4-1

4.1 Introduction ........................................................................................................................................... 4-1

4.2 Load Rating ............................................................................................................................................ 4-1

4.3 Posting ................................................................................................................................................... 4-7

CHAPTER 5 : SCOUR EVALUATION .................................................................................. 5-1

5.1 Introduction ........................................................................................................................................... 5-1

5.2 Scour Critical Bridges .............................................................................................................................. 5-1

CHAPTER 6 : BRIDGE RECORDS ...................................................................................... 6-1

Table of Contents

December 2021 ii

CHAPTER 7 : INSPECTION REPORT ................................................................................. 7-1

7.1 Introduction ........................................................................................................................................... 7-1

7.2 Cover Sheet ............................................................................................................................................ 7-2

7.3 Structure Summary ................................................................................................................................ 7-3

7.4 Recommendations and Estimated Costs ................................................................................................. 7-5

7.5 Field Inspection Report .......................................................................................................................... 7-9

7.6 Structure Load Rating ........................................................................................................................... 7-11

7.7 Structure Inventory and Appraisal........................................................................................................ 7-11

7.8 Profile Sheets ....................................................................................................................................... 7-12

7.9 Additional Photos................................................................................................................................. 7-12

CHAPTER 8 : QUALITY CONTROL AND QUALITY ASSURANCE ..................................... 8-1

8.1 Introduction ........................................................................................................................................... 8-1

8.2 Field Review of Inspection Teams .......................................................................................................... 8-1

8.3 Field Review of Inspection Findings ........................................................................................................ 8-1

8.4 Bridge Inspection Refresher Training Requirements ............................................................................... 8-1

8.5 Bridge Inspection Report Checking Procedures ...................................................................................... 8-2

Appendices Fracture Critical Plan Scour Critical Plan Interim Inspection Report Damage Inspection Report Damage Inspection Report Critical Findings Report Interim Inspections for NPS Railroad Bridges Load Rating Summary Sheets Bridge Inspection Field Review Form

Introduction

December 2021 1-1

CHAPTER 1 : INTRODUCTION

The Federal Lands Highway (FLH) Bridge Inspection Program (BIP) provides direct program oversight, performs safety inspections of bridges, and load rates bridges owned by Federal Agencies. The FLH Bridge Inspection Program provides technical leadership and support to the Federal Highway Administration (FHWA) and other Federal Agencies through technology advancement, bridge inspection technical assistance, and bridge inspection program policy and guidance.

Bridge inspection activities are performed in accordance with the National Bridge Inspection Standards (NBIS) published in the Code of Federal Regulations, 23 CFR 650, Subpart C. The NBIS set the national standards for the proper safety inspection, evaluation, and inventory of public bridges ensure that are in safe and usable condition.

The NBIS define a bridge as a structure including supports erected over a depression or an obstruction, such as water, highway, or railway. It has a track or passageway for carrying traffic or other moving loads and has an opening measured along the center of the roadway of more than 20 feet between under copings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes. It may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening.

This manual will address all bridges meeting this definition, including small bridges and culverts that are less than 20 feet, non-public bridges, pedestrian bridges, and railroad bridges that are considered non-National Bridge Inventory (NBI).

The FLH Bridge Inspection Program Manual is intended to ensure the proper safety inspection and evaluation of bridges owned by Federal Agencies, standardize reporting procedures, and provide the guideline to complying with the NBIS, FHWA and FLH requirements. This manual is not intended to be a step-by-step instruction, nor will it identify all current office policies for specific operations. Specific guidelines should always be obtained from the FLH Program Manager (as defined in Chapter 2.2). Bridge inspection personnel may find additional guidance in, but not limited to, the most current editions of the following:

● Bridge Inspector’s Reference Manual (BIRM)

● AASHTO Manual for Bridge Evaluation (MBE)

● AASHTO Inspection of Fracture Critical Members

This manual will be continuously updated to reflect new policies and other changing conditions.

It is encouraged to refer to this manual often so that policies are applied consistently and thoroughly. As this manual is written primarily for FLH Bridge personnel, some content may not apply to consultant inspection teams.

Inspection Program Requirements

December 2021 2-1

CHAPTER 2 : INSPECTION PROGRAM REQUIREMENTS

2.1 Bridge Inspection Organization

The NBIS requires Federal Agencies to have a bridge inspection organization to inspect, or cause to be inspected, all highway bridges located on public roads within their jurisdiction. The bridge inspection organization must provide quality control (QC) and quality assurance (QA) for their policies and procedures, and maintain a current bridge inventory, including records of the inspection reports, load ratings, and other NBIS requirements. A qualified Program Manager is charged to administrate the bridge inspection organization.

2.2 Responsibilities and Qualifications of Personnel

The following section describes the responsibilities and minimum qualifications of FLH Bridge Inspection Program personnel in compliance with the NBIS.

Program Manager

The FLH Program Manager is responsible for setting all bridge inspection policies and procedures, assuring compliance with all NBIS requirements. The FLH Program Manager shall also review and approve inspectors’ qualifications, and also schedule the required training for in-house inspectors, as needed, in order to keep their inspection qualifications up to date.

The FLH Program Manager must have successfully completed an FHWA-approved comprehensive bridge inspection training course and either be a registered Professional Engineer (PE) or have ten years of bridge inspection experience.

Inspection Team Leader

The Inspection Team Leader is the individual in charge of an inspection team responsible for planning, preparing, and performing the field inspection of bridges. A qualified Inspection Team Leader is always required to be present during a bridge inspection. The Inspection Team Leader will be updating inventory data and preparing the formal inspection reports.

The Inspection Team Leader must have successfully completed an FHWA-approved comprehensive bridge inspection training course and meet one of the following qualifications:

● Registered Professional Engineer (PE); or

● Five years of bridge inspection experience; or

● Certified as a Level III or IV Bridge Safety Inspector by the National Institute for

Certification in Engineering Technologies (NICET); or

● Bachelor’s degree in engineering from a college or university accredited by the

Accreditation Board for Engineering and Technology, successfully passed the Fundamentals of Engineering Exam, and two years of bridge inspection experience; or

December 2021 2-2

● Associate degree in engineering or engineering technology from a college or university accredited by the Accreditation Board for Engineering and Technology and four years of bridge inspection experience.

EFL Inspection Team Leader must successfully complete periodic bridge inspection refresher training course to remain qualified.

Inspection Team Member

The Inspection Team Member accompanies and assists the Inspection Team Leader during field bridge inspections. Typical duties include helping to organize bridge inspection trips, taking measurements, documenting findings, taking photographs, and providing support in the preparation of the inspection report as needed.

The NBIS does not set specific training or educational requirements for the Inspection Team Member. However, Inspection Team members are encouraged to take the FHWA-approved comprehensive bridge inspection training course and other FHWA training listed in the BIRM.

Inspection Team Member must be familiar with NBIS, FHWA Recording and Coding Guide, and this manual.

Load Rating Engineer

The Load Rating Engineer determines the safe carrying capacity of each bridge as required by the NBIS. The individual(s) responsible for load ratings must be a registered PE or be supervised by a registered PE. Load rating calculations of bridges are performed and maintained by the Load Rating Engineer.

Underwater Bridge Inspection Diver

An Underwater Bridge Inspection Diver must successfully complete either an FHWA-approved comprehensive bridge inspection training course or an FHWA-approved underwater bridge inspection diver training course.

Nondestructive Testing Specialists

Individuals performing nondestructive testing (NDT) shall be qualified in accordance with American Society for Nondestructive Testing (ASNT).

Bridge Inspection Consultant

The Bridge Inspection Consultant is a prequalified consulting firm who is responsible for all contracted inspections. Consultant inspection team must have an Inspection Team Leader during all bridge inspections that meet the same qualifications specified for the Inspection Team Leader.

December 2021 2-3

2.3 Bridge Inspection Inventory

The FLH Bridge Inspection Program prepares and maintains an inventory of all bridges per NBIS requirement on behalf of other Federal Agencies. Collected for each bridge, is the Structure Inventory and Appraisal (SI&A) data which is transmitted to the FHWA in accordance with Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges.

The bridge inventory for FLH Bridge Inspection Program is managed using the InspectTech.

InspectTech records bridge inspection data, including SI&A data and generates inspection reports in accordance with FLH reporting requirements.

InspectTech contains a data tracking feature that records the report creation date. All bridge inspection SI&A data collected shall be entered into InspectTech within 90 days of the field inspection.

2.4 Inspection Types and Frequencies

There are seven types of inspection: Initial, Routine, Fracture Critical Member, Underwater, Damage, In-Depth, and Special (interim). The NBIS specifies frequency requirements for each type of inspections. The FLH Program Manager, with the bridge owner concurrence, will determine the appropriate inspection type for a bridge. Inspection frequencies may increase or decrease due to factors such as age, condition, and bridge design.

Initial Inspection

An Initial Inspection is the first baseline inspection conducted on every new bridge, after a major rehabilitation, when configuration or geometry of a bridge changes or when bridge ownership change. Initial Inspections are also used when bridge is discovered that has not been previously inventoried.

Inspectors must perform a fully documented investigation to identify any deficiencies, record all SI&A data, and verify bridge geometric data for entry into InspectTech. With the information collected during the inspection, the bridge will be evaluated to determine whether other inspections will be throughout its life, including Fracture Critical, Special, or Underwater Inspections.

An Initial Inspection should be completed within 90 days of the date a newly constructed or rehabilitated bridge is open for service. Initial Inspection data, including the SI&A data, must be entered into InspectTech within 90 days of inspection.

Routine Inspection

Routine Inspections are regularly scheduled inspections consisting of observations and measurements to determine the physical and functional condition of the bridge, to identify any changes from previously recorded conditions, and to ensure that the bridge continues to satisfy present service requirements.

December 2021 2-4

Routine Inspections are conducted visually from the deck, ground, water-level, or from permanent work platforms and walkways of all components of the structure, channel, and adjacent roadway.

During the inspection, the inspection team shall document and photograph any deterioration, defect, and damage to the bridge. The inspectors must verify and update SI&A data.

In accordance with NBIS, Routine Inspections is performed at regular intervals not to exceed 24 months. However, the inspection frequency may vary, increasing or decreasing, depending on the bridge condition. The inspection frequency for each structure is to be reviewed following each inspection, and either verified or adjusted as necessary.

• Inspection intervals less than 24 months may be required for bridges with a NBI component condition coding of poor or have a Priority of Improvement of ‘A’ or ‘B’ (as defined in Chapter 7.4). The Inspection Team Leader should consult with the FLH Program Manager to decide if reducing the inspection interval is appropriate given the bridge condition.

• Routine Inspection intervals greater than 24 months, not to exceed 48 months, may be approved when past inspection findings and analysis justify increasing the inspection intervals. Written FHWA-Headquarter approval and consent from bridge owner is required when increasing inspection intervals to greater than 24 months.

Fracture Critical Inspection

Fracture Critical Inspections are regularly scheduled hands-on (within arm’s length of the component) inspections to examine non-redundant steel tension members or member components of a bridge that have no load path redundancy. Non–redundant members are defined as steel members in tension, or with a tension element, whose failure would probably cause a portion of or the entire bridge to collapse. A Fracture Critical member inspection plan containing the required procedures and information shall be developed for each fracture critical bridge, using the form(s) provided in the appendices, and placed in the bridge file. The procedures outlined in the plan are to be followed for each Fracture Critical Inspection. This plan shall include a description and location of the Non–redundant member; the location of fracture and fatigue prone areas, including a sketch or other visual representation of each detail type; inspection procedures including NDT; and the inspection frequency. The findings of each Fracture Critical inspection are to be recorded in a stand-alone report, or as part of the routine inspection report, including specifically noting that the inspection is a Fracture Critical type.

Typical examples of Non–redundant members are two-truss systems, two girder systems, steel pier caps and cross girders, welded tied arches, suspension systems with eye bar components and pin and hanger connections on two or three girder systems. Some fracture critical detail, such as pin and hanger connection and category ‘D’ or ‘E’ fatigue-prone details on redundant load path bridges, will require a Special Inspection.

Inspection intervals less than 24 months may be required for bridges with a NBI component condition coding of poor or have a Priority of Improvement of ‘A’ or ‘B’. Inspection Team Leader

December 2021 2-5 should consult with the FLH Program Manager to decide if reducing the inspection interval is appropriate given the bridge condition.

Refer to the FHWA Bridge Inspector’s Reference Manual (BIRM) and AASHTO Manual for Bridge Evaluation (MBE) for more detailed information on inspection of FCMs and planning procedures.

Underwater Inspection

An Underwater Inspection is the inspection of the underwater portion of a bridge substructure and the surrounding channel, which cannot be inspected visually at low water by wading or probing, and generally requires diving or other appropriate procedures.

Underwater diving inspections shall be conducted in accordance with the requirements for Level I, II, and III inspections, which originated in the offshore diving industry and adopted by the United States Navy. The standard underwater inspection for FLH Bridge Inspection Program is Level II inspection.

Underwater Inspection levels are described below:

● Level I Inspection

The Level I inspection consist of a close visual or tactile inspection at arm length with minimal cleaning to remove marine growth of the submerged portion of the bridge. The inspection is conducted over the entire exterior surface (100%) of underwater elements.

Level I inspection must be detailed enough to detect obvious major damage or deterioration due to overstress or other severe deterioration.

● Level II Inspection

The Level II inspection is directed toward detecting and identifying damaged/deteriorated areas which may be hidden by bio fouling or surface deterioration. It is typically performed on at least 10 percent of the underwater elements. The inspection requires cleaning of the structural elements in 1-foot-high bands at the mud line, waterline and half way between.

● Level III Inspection

The Level III inspection consists of a highly detailed inspection of a critical structural area/element of the underwater structure to detect hidden or interior damage and loss in cross-sectional area. This level of inspection will often require the use of non-destructive testing (NDT) techniques but may also require the use of partially destructive techniques such as sample coring, material sampling or in-situ surface hardness testing.

Each bridge requiring an Underwater Inspection shall have bridge-specific inspection procedures identifying underwater elements and inspection frequency. These procedures should also outline required equipment, inspection methods, and permits, identify physical scour countermeasures, and describe risk factors specific to the particular bridge. These procedures must be documented and included in the bridge file. The bridge must be inspected according to these procedures.

In accordance with NBIS, underwater structural elements must be inspected at a regular interval not to exceed 60 months. However, the inspection frequency may vary, increasing or decreasing, December 2021 2-6 depending on the bridge condition. Inspection intervals less than 60 months may be required for bridges with a NBI component condition coding of poor or when the structure has been coded as scour critical. Any bridge with NBI item 113 equal to 0, 1, 2, 3, 4 or 7 may not be placed on a 48 month inspection interval. Inspection Team Leader should consult with the FLH Program Manager to decide if reducing the inspection interval is appropriate given the bridge condition.

Damage Inspection

A Damage Inspection is an unscheduled inspection that is undertaken to assess the structural damage caused by environmental or human actions. Potential events that may call for a Damage Inspection include flood, fire, earthquakes, and vehicle/vessel impact. The scope of the inspection will be detailed by the FLH Program Manager, and should be of sufficient detail to determine if emergency load restrictions or closure of the bridge to traffic is necessary and to determine what repairs are necessary.

Damage Inspections shall be conducted as soon as the FLH Program Manager is contacted by any Federal Agency about the damage. A thorough examination of the damaged areas should be made to determine the need for load restrictions or closure to traffic, and to provide recommended actions. The inspectors will need to identify any fractured members, measure any section loss, misalignment of members, loss of foundation support, and any other deficiencies.

The Inspection Team Leader must record all inspection findings, photos, and recommended actions on the Damage Inspection Report. The database (InspectTech) must be updated to include the damage inspection findings. A copy of the Damage Inspection form should be placed in the bridge file. A follow-up letter must also be sent to the bridge owner to report damage findings.

Special Inspections following the initial damage inspection should be scheduled by FLH Program Manager to monitor damage.

In-Depth Inspection

An In-Depth Inspection is a more detailed inspection of one or more bridge members to identify and assess any deficiencies not readily detectable using Routine Inspection procedures. Special equipment, such as under-bridge inspection equipment, staging, and workboats, should be provided to obtain access, when needed. If necessary, NDT and/or material tests may be required to fully ascertain the existence or extent of deficiencies.

In-Depth Inspections may be required for bridges with a NBI component condition coding of poor, or any other reason deemed appropriate by the FLH Program Manager.

In-Depth Inspections should be conducted at 24 to 60 month intervals depending on the condition of the bridge, but an increased inspection frequency may be considered. The FLH Program Manager will determine the appropriate inspection frequency.

December 2021 2-7

Interim Inspection

An Interim Inspection is performed just as a Routine Inspection without a full inspection report completed. The Inspection Team Leader must report all findings on the Interim Inspection Report.

See the appendices for a blank form. A full inspection report must be completed only if there are significant changes in the condition of the structure. Interim Inspection is applicable on the following cases:

• An Interim Inspection will be conducted 24 months after a Routine Inspection for bridges with inspection interval of 48 months.

• An Interim Inspection will be conducted 12 months after a Routine Inspection for NBI structures that either qualify as structurally deficient, or have a Priority of Improvement of ‘A’ or ‘B’.

• An Interim Inspection will be conducted for on railroad bridges. Railroad bridges are inspected annually and a full inspection report is generated on interval of 24 months. See the appendices for a blank form

Special Inspection

Special Inspections are scheduled at the discretion of the FLH Program Manager, on behalf of any Federal Agency requesting the inspection, to monitor a particular known or suspected deficiency, such as foundation settlement, scour (undermining), or member conditions that may have an impact on the structural integrity of the structure. Special Inspections usually are not sufficiently comprehensive to meet NBIS requirements for Routine Inspections. The Inspection Team Leader, in conjunction with the FLH Program Manager, will develop an inspection procedure and the appropriate reporting method.

Special Inspections are also required for complex bridges. Complex bridges are movable, suspension, cable stayed, and other bridges with unusual characteristics. According to the NBIS, each complex bridge in the inventory must have specialized inspection procedures and Inspector must have specialized training and experience to inspect does. The bridge must be inspected according to these procedures, by appropriately trained inspectors. Inspection requirements for complex bridges are defined case by case in a Scope of Work (SOW)

Inspection Procedures

December 2021 3-8

CHAPTER 3 : INSPECTION PROCEDURES

3.1 Preparation for Inspection

Before inspecting a bridge, the Inspection Team Leader must prepare and plan a safe and efficient inspection procedure. The bridge inspection team should obtain and review previous inspection reports, original design plans, as-built plans, rehabilitation, and maintenance history to anticipate actions needed in the field (including special testing, studies, or monitoring needed). Necessary inspection equipment should be assembled and shipped (if needed). Print copies of the previous inspection report to use in the field.

Inspection Team Leader must contact Federal Agency by letter and phone after upcoming inspection. A standard visit letter will be sent to the superintendent four weeks before the inspection, and a phone call, two weeks before the inspection, to the Chief of Maintenance to advise them of the visit, make arrangements to meet, and discuss any courtesy (one-time only) inspections they may desire.

3.2 Field Inspection Equipment

Inspectors need the correct tools to perform their job safely, effectively, and efficiently. Some of the tools and equipment used by inspectors are mentioned in this section. Refer to the BIRM (Chapter 2 – Topic 2.3 – Inspection Equipment) for a complete list.

Inspectors must be trained in the proper use of all equipment, safety procedures for each type of equipment, and inspection procedures. Inspection equipment may require means to secure it to the inspector or the structure to prevent the equipment from falling on persons or vehicles passing under the structure.

Personal Equipment

During inspection, inspectors should wear rugged clothing suitable for climbing that will not catch on structure. Hard hat and reflective vest must also be worn during all types of inspections and life jackets must be worn when in a boat or when in the Under Bridge Inspection Vehicle (UBIV) bucket over water.

Standard Equipment

Recommended basic equipment to be carried during each inspection includes: hammers, sounding/probing rods, flashlights, folding rules, reel tape measures, binoculars, crack width monitors, and keel/crayon marking devices. Other standard equipment includes chain drag, timber drill and coring tool, timber probe, string, plumb bob, boat, ladder, wire brush, moisture meter, and dye penetrant.

December 2021 3-9

Special Equipment

The following portable equipment is used when necessary or when specifically planned as part of a Routine Inspection in some instances.

● Site Level or Transit: use to quantify and monitor serious settlement and deflections; a stretched string is adequate for most instances

● Crack Monitors: used to monitor crack growth or movement

● Magnetic Particle Testing: Devices for detecting cracks in steel members

● Ultrasonic Testing (Consult an NDT specialist)

● Portable Concrete Coring Machine

Documentation Material

Common tools used for documentation include the following:

● Laptop or other field computers for limited data entry when required

● Digital cameras, memory cards, underwater camera, batteries, battery chargers

● Copy of previous inspection report, plans for newly built or rehabilitated structures

● Blank inspection report forms and element level data sheets

3.3 Safety Practices

Inspection Team Safety

Safety is the primary concern while performing any type of inspection. To minimize the chance of an inspector becoming injured, all inspectors in the field should adopt the following work habits:

● Never work alone

● Be well-rested and alert

● Stay in good health and maintain a level of good physical conditioning

● Be familiar with using the proper tools

● Do not use broken equipment

Inspection teams must operate in a group of two or more when performing any type of inspection.

Appropriate personal protective protection equipment, such as safety vest, steel-toe boots, and hard hats should be worn at all times. All inspectors must always carry their office mobile phone for use in case of an emergency or so that someone from the office can contact them if necessary.

When climbing on structural members, always use a safety harness. Wading should only be done in low velocity channels with shallow water. Do not do attempt climbing or wading that you feel is beyond your physical ability or unsafe for any reason. If a member or area of a structure could not be adequately inspected, inform the FLH Program Manager and state this in the ‘Remarks’ section of the report; arrangements will be made for access in future inspections.

December 2021 3-10

Public Safety

Inspectors should be aware of the flow of traffic and pedestrian activity on and under the structure when performing any inspection fieldwork. To protect the public, an inspection should be planned to minimize disruptions to vehicle or pedestrian traffic by using appropriate traffic control.

If an inspection is performed in an UBIV or a bucket truck, all tools and equipment must be secured in order to prevent them from falling onto pedestrians or traffic below.

Traffic Control

Traffic control requirements should be reviewed before performing an inspection to assure the safety of the inspection team and the traveling public. The Inspection Team Leader should verify with Federal Agency representative before the inspection if traffic control is needed to inspect the bridge. When the UBIV is used to perform an inspection, the Inspection Team Leader should make sure the traffic control and signs are correctly set up.

3.4 Field Documentation

Field Documentation is essential for any type of inspection. Inspectors shall document conditions of bridge member or component, including any deficiencies found during the inspection, with detailed field notes, voice recording device, and with photographs.

Measurements

Measurements during field inspection are made to provide updated data on existing structure components and to track changes in deficiencies. Deficiencies such as cracks, spalls, and delamination can change over time; therefore, it is important that the initial measurements are acquired in a manner that can be replicated during future inspections.

Profile (vertical) measurements should be taken at both the upstream and downstream sides of bridge over water during Routine Inspections. Measurements at all substructure units, both upstream and downstream, should be taken during an initial inspection as a baseline.

Measurements for vertical clearance should be taken during Routine Inspection for NBI bridges over roadways and for tunnels, if known clearance is less than 16 feet. For known clearances of 16 feet and over, measurements should be taking when an obvious change in clearance occurs due to an overlay or rehabilitation. Clearances should be measured above each lane at both sides of the bridge or at both portals as a minimum, for each direction of traffic.

Measurements of superstructure elements should be obtained if there is measurable section loss, for new load rating calculation. Also, if plans are not available and a load rating has never been calculated, then the primary superstructure elements should be measured.

December 2021 3-11

Photographs

Photographs are a very important documentation tool used by an inspection team for illustrating bridge conditions. All photographs shall be taken using digital cameras. Pictures taken should be well composed, trying not to show vehicles or people. A scale or inspection tool (e.g. hammer, pencil, etc.) may be placed on the deficient area in order to provide a frame of reference for photograph. It is important to include in the photo captions or record the exact location of where the photograph was taken and a description of the picture.

The following general pictures shall be taken during every inspection:

● A view of each approach, looking toward the bridge with all topside deck element visible

● General topside and underside deck views,

● An elevation view of each side of the bridge

● General view of each type of abutment and pier

● A view looking upstream and downstream from the bridge, for bridges over water (include a small portion of the structure in the foreground of the photo for reference)

● Posting signs, if the bridge has load restrictions or clearance

Additional pictures shall be taken to document all structural deficiencies, erosion, settlement, scour conditions and any other features that the Inspection Team Leader considers important.

For bridges that require underwater inspections, an underwater camera should be used to document condition of underwater bridge elements when practical. In most underwater conditions, a clear Plexiglas box should be placed against the element, between the element and the camera to produce a clear photo.

3.5 Critical Finding

A critical finding is defined as a structural or safety deficiency that may cause partial or total collapse or serious traffic safety hazard if not addressed immediately. Critical findings are defined as follows:

Primary Code 0 – Critical: Immediate attention required (within 24 hrs.).

Primary Code 1 – High Priority: Attention required within 30 days.

Inspection Team Leaders must immediately contact the FLH Program Manger when a potential critical finding is identified. Inspection Team Leaders must then notify the Facility Manager or Chief of Maintenance of the critical findings.

A Critical Finding Report describing the extent of the deficiency, complete with photos, measurement, possible cause and recommendations for repair is to be created in a timely manner. See the appendices for the Critical Finding Report. A follow-up letter should then be sent to the NPS or other Federal agency describing the critical finding including the Critical Finding Report.

December 2021 3-12

All critical findings should be followed up by the appropriate inspection to ensure all issues have been addressed, and that the bridge is safe to be used by the public.

Inspection Team Leaders do not have the authority to close a bridge but are to follow the FLH Critical Finding protocol outlined in the flow chart shown on the next page.

December 2021 3-13

Federal Lands Highway Protocol Flow Chart for Critical Findings

Yes

Critical Finding

Finding Still Deemed Critical?

Recommend Bridge Closure or open with restriction?

Safety Bridge Inspection

Yes No

Call: FLH Program Manager and Partnering Federal Agency representative

Document damage in Inspection Report; take photos; and continue monitoring

No

Yes No

Send a follow-up letter (or form) to the partnering Agency detailing deficiencies, repair recommendations and complete inspection

Complete critical findings report Send copies of reports to the following:

• FLH Bridge Engineer

• NPS Chief of Transportation

• NPS Service Bridge Engineer

• NPS Park Superintendent

• NPS Chief of Maintenance

• Other Partnering Agency

Representative

Complete inspection, reduce bridge Condition rating and further evaluate

December 2021 3-14

3.6 Post-Inspection De-Briefing

It is recommended to complete all data collection and inspection notes, including condition codes and recommendation ideas, while at the bridge site. It is easy to forget about a recommendation or the exact condition of an element unless everything is documented in the field. Also, review photos taken by an inexperienced photographer to ensure that all necessary photos were captured and that quality is satisfactory.

The Inspection Team leader should meet with FLH Program Manager after the inspection to discuss the following:

● Serious, critical, or unusual findings

● Significant requests, remarks from clients

● Significant repairs or other work done

Load Rating and Posting

December 2021 4-1

CHAPTER 4 : LOAD RATING AND POSTING

4.1 Introduction

All National Bridge Inventory (NBI) bridges are to be load rated in accordance with the AASHTO Manual for Bridge Evaluation, 2nd edition (MBE). The purpose of a load rating calculation is to provide a basis for determining the safe load capacity of a bridge and to determine the safe use of a bridge for posting and permit decisions. Load ratings are based on information in the bridge file including results of a recent inspection.

An updated load rating calculation is required whenever the capacity of the bridge changes due to changes in the dead load or the condition of the structure. If load rating calculations need to be updated, the inventory data must also be updated to reflect the actual load capacity. The Inspection Team Leader must notify the Load Rating Engineer if a bridge needs to be load rated based on the current findings. The Load Rating Engineer shall be responsible for ensuring the load rating of the bridge is performed in a timely manner.

The goal is to have complete, accurate, and realistic load capacity ratings that have been developed in a consistent manner for all bridges under FLH responsibility. These load ratings will eventually determine the need for posting and closure requirements, but in many cases will help to determine rehabilitation or complete replacement needs. A copy of each rating shall be maintained in the individual bridge records.

Load ratings, for new or rehab bridges, should be completed by the design engineer. The load rating calculations should be summarized and a copy forwarded to the FLH Load Rating Engineer for inclusion in the appropriate bridge inspection file.

4.2 Load Rating

As per FHWA requirements, bridges designed with the Load and Resistance Factor Design (LRFD) method or designed after October 1, 2010, load rating calculation will be performed using the Load and Resistance Factor Rating (LRFR) method.

Bridges designed with other methods can be load rated using LRFR, Load Factor Rating (LFR), or Allowable Stress Rating (ASR) methods depending on the type of structure. Steel and concrete structures designed with ASD must be load rated using either LFR or LRFR methods. Timber and masonry structures should be load rated using ASR. Load rating calculations using the LFR and ASR methods shall be done in accordance with the current Manual for Bridge Evaluation.

Assumptions

All assumptions made should be clearly stated. For consistency between ratings, the following assumptions are normally used:

1. Impact (LFR only):

December 2021 4-2

As stated in the AASHTO Manual for Bridge Evaluation subsection 6B.6.4, “...impact may be reduced when conditions of alignment, enforced speed posting, and similar situations require a vehicle to substantially reduce speed in crossing the structure.”

The maximum impact factor used should be 1.3 for vehicular bridges. Impact factors should be reduced, when applicable, to reflect actual conditions where there are obvious cases of reduced speed, such as on specific NPS roads in campgrounds or similar areas, or where speeds are low due to alignment or proximity to an intersection. However, for rough or settled surfaces or other approach conditions that obviously produce noticeable impact onto the structure, this maximum impact factor should be used regardless of any reduced speed conditions. In general, any reductions should be made using sound engineering judgment and the following table as guidance:

REDUCED IMPACT

FACTOR CONDITIONS

1.2 speed limit or expected speeds approx. 25-35 mph

1.1 speed limit or expected speeds approx. 15-25 mph

1.0 Only for supervised permit loads for speeds 5-15 mph

If actual conditions are not known, including speeds normally used by vehicles, then conservative estimates may be used based on observations made at the bridge site including approach roadway conditions, roadway and bridge alignment, etc.

2. Lateral distribution of loads:

As stated in the AASHTO Manual for Bridge Evaluation, Subsection 6B.6.3, for lateral distributions ‘The option exists to substitute field measured values, analytically calculated values, or those determined from advanced structural analysis methods based on the properties of the existing structure’. These alternate methods should be used when applicable to reflect actual loading conditions. For two-beam systems, live load distribution factors should be calculated via lever rule based on placement of the vehicle wheel 1 foot from the curb line. Placement of the assumed wheel line on existing running planks or other delineated wheel paths is acceptable if it is field-verified that vehicles consistently follow the delineated path.

3. Longitudinal distribution of loads:

For longitudinal timber running planks (runners) on transverse timber deck planks, the runners are assumed to distribute wheel loads over 2 or more deck planks, depending on the thickness of runners and width of deck planks. For example, assume 2" thick runners to distribute loads over two 10" or wider planks, or over three 8” or narrower planks; assume 3" thick runners to distribute loads over one additional plank than for 2” thick runners. These values are conservative estimates based on observed loads on numerous plank-and-runner timber decks over an extended period of time.

4. Running planks:

December 2021 4-3

If wheel loads are placed directly over beams via running planks or other delineators, a timber deck does not need be rated; however, it needs to be noted in the calculations that the live loads are assumed to remain on the runners. Again, it should be field-verified that larger vehicles actually remain on the runners, particularly when turning onto or off of the bridge at curved alignments.

Load Rating for Timber

If the timber species and grade is unknown, assume Southern Yellow Pine for bridges in EFL’s jurisdiction (1st tier of States west of the Mississippi and east), and Douglas Fir for bridges in CFL’s and WFL’s jurisdiction. Based on field observations, assign one of the 3 lumber grades:

● #1 (non-dense): generally clear and free of significant defects

● #2 (non-dense): contains some small and medium sized knots

● #3 (non-dense): generally contains some large knots or other significant defects

Use the appropriate Adjustment Factors when applicable; for most bridges this will include one or more of the following:

● Flat Use factor - for plank decks

● Repetitive Member factor - nail-laminated decks, and multi-stringer less than or equal to

24” O.C.

● Wet Service factor - use for all bridges, unless superstructure elements are fully protected from excessive moisture

● Shear Stress factor – for timber free of splits (complete separation of the member), use 2.0;

use 1.0 otherwise

● Load Duration factor – for low ADT bridges (<= 400), use 1.25; for higher ADT and long-term construction conditions use 1.0; for permit loading use, up to 1.6 if there are no signs of distress or significant defects in the primary timber members, and the moving load is not permitted to stop on the bridge

Timber members with any loss of capacity due to deterioration from decay should not be calculated for an Operating Rating (Operating Rating value should equal Inventory Rating).

Generally, a design engineer shall perform all ratings, and be reviewed by a Professional Engineer prior to acceptance. However, for ratings done concurrent with new designs, this check may not be necessary if the calculated rating values meet or exceed the design loading.

Load Rating for Bridges without Plans

For bridges where necessary details for load rating are not available from plans or field measurements; knowledge of the live load used in the original design, the current condition and/or live load history of the structure may be used to provide a basis for assigning a safe load capacity.

If the structure has been carrying highway traffic and shows no signs of distress, it can be assumed that the structure can carry legal loads. When signs of distress are evident, the effect of the distress on the load carrying capacity of the structure must be considered. When assuming a rating, consideration must be given to reducing the load carrying capacity of the structure to some

December 2021 4-4 level below legal limit. The appropriate assumed load limit shall be determined on a case by case basis and using engineering judgement.

Load Rating Criteria:

● Assign a Load Rating equal to the Legal Load Limit, for the design vehicle, to structures with condition rating of 6 or above for Items 58, 59 and 60 or Item 62. Determine the Load Rating for the remaining vehicles by Live Load Comparison.

● For structures with condition rating of 5, for Items 58 or 59 or 60 or 62, assign a an Operating Load Rating equal to the Gross Vehicle Weight for all trucks and apply a Live Load Reduction Factor (1.67 for Steel and Concrete, 1.33 for Timber, and 1.0 for Masonry) to determine the Inventory Rating.

● For structures with condition rating of 4 or below, assign an Operating Load Rating equal the Gross Vehicle Weight for all trucks and apply a Live Load Reduction Factor (1.67 for Steel and Concrete, 1.33 for Timber, and 1.0 for Masonry) to determine the Inventory Rating. Reduce the Operating Load Rating below the GVW, on a case by case basis, when signs of distress are evident. Also, Nondestructive Load Testing may be considered for these structures in accordance with provisions in the MBE.

December 2021 4-5

December 2021 4-6

Inventory and Operating Ratings

Show Inventory and Operating ratings for all truck types, including the Specialized Hauling Vehicles, based on a full load rating calculation if available. In the absence of a full rating calculation, the known or assumed design loading should be used to determine temporary Inventory and Operating ratings for all truck types. These Inventory ratings should be obtained by using the AASHTO tables to calculate ratios of moments produced by each truck type for a particular span length. The Operating ratings are then obtained by multiplying these Inventory numbers by 1.0 for masonry, up to 1.33 for timber, and by 1.67 for most other materials. For timber, an Operating rating equal to the Inventory rating can be chosen if advanced deterioration is present. When the design load is used as the Inventory rating, a corresponding default statement should be placed under ‘Remarks’ of the Load Rating Summary Sheets.

A full load rating calculation should be completed prior to transmittal of an inspection report when any of the following apply, when a calculation has not yet been completed:

● Distress in the main structural elements is observed

● Significant loss of section or deterioration has occurred in any primary structural element

● The design loading is unknown, and the size/strength of the primary structural elements can be determined from field measurements, construction notes or photos, or other practical means

If the strength of a primary element cannot be determined, such as with concrete structures of unknown reinforcing, then a conservative design loading must be assumed. When a structure experiences signs of distress and/or significant deterioration of a primary element, then the Inventory and Operating ratings should be lowered based on sound engineering judgment using previous experience with similar structures as a guide. A load rating should then be recalculated before report transmittal if a structure experiences significant additional distress or deterioration, or if it rates for somewhat less than the acceptable Operating rating defined above from a ‘working stress’ calculation, but may rate at an acceptable level using the LF method.