Bridge inspection plays an important role in providing a safe infrastructure for the nation. As the nation’s bridges continue to age and deteriorate, an accurate and thorough assessment of each bridge’s condition is critical in maintaining a dependable highway system.
There are seven basic types of inspection:
These inspection types are presented in Article 4.2 of the AASHTOManual for Bridge Evaluation. Although this topic is organized for “in-depth” inspections, it applies to any inspection type. However, the amount of time and effort required for performing each duty vary with the type of inspection performed.
This topic presents the duties of the bridge inspection team. It also describes how the inspection team can prepare for the inspection and some of the major inspection procedures. For some duties, the inspection program manager may be involved.
There are five basic duties of the bridge inspection team:
Planning is necessary for a safe, efficient, cost-effective inspection effort which results in a thorough and complete inspection of in-service bridges.
Basic activities include:
Preparation measures needed prior to the inspection include organizing the proper tools and equipment, reviewing the bridge structure files, and locating plans for the structure. The success of the on-site field inspection is largely dependent on the effort spent in preparing for the inspection. The major preparation activities include:
The first step in preparing for a bridge inspection is to review the available sources of information about the bridge, such as:
Each of these sections of the bridge structure file is presented in detail in Topic 4.4.2.
Another important activity in preparing for the inspection is to establish the structure orientation, as well as a system for identifying the various components and elements of the bridge (see Figure 2.1.1). If drawings or previous inspection reports are available, use the same identification system during the inspection as those used in these sources.
Figure 2.1.1 Sample Bridge Numbering Sequence
Establish an identification system if there are no previous records available. The numbering system presented in this topic is one possible system, but some states may use a different numbering system.
This route direction information can be used to identify the location of the bridge.
Route direction would be north, south, east or west. Mile markers, stationing or segments are the locations along the route. Location of the bridge can be identified by the route direction along with mile marker, stationing or segment information.The route direction can be determined based on mile markers, stationing, or segments, and use this direction to identify the location of the bridge.
The deck sections (between construction joints), expansion joints, railing, parapets, and light standards are included in the deck element numbering system. Number these elements consecutively, from the beginning to the end of the bridge.
The spans, the beams, and, in the case of a truss or arch, the panel points are included in the superstructure element numbering system. Number the spans consecutively, with Span 1 located at the beginning of the bridge. Multiple beams are to be numbered consecutively from left to right facing in the route direction. Similar to spans, floorbeams are also numbered consecutively from the beginning of the bridge, with the first floorbeam labeled as Floorbeam 0. This coordinates the floorbeam and the bay numbers such that a given floorbeam number is located at the end of its corresponding bay.
For trusses, number the panels similarly to the floorbeams, beginning with Panel Point 0. Label both the upstream and downstream trusses. Points in the same vertical line have the same number. If there is no lower panel point in a particular vertical line, the numbers of the lower chord skip a number (see Figure 2.1.2). Some design plans number to midspan on the truss and then number backwards to zero using prime numbers (U9’). However, this numbering system is not recommended for field inspection use since the prime designations in the field notes may be obscured by dirt.
Figure 2.1.2 Sample Truss Numbering Scheme
The abutments and the piers are included in the substructure element numbering system. Abutment 1 is located at the beginning of the bridge, and Abutment 2 is located at the end. Number the piers consecutively, with Pier 1 located closest to the beginning of the bridge (see Figure 2.1.2). Alternatively, the substructure units may be numbered consecutively without noting abutments or piers.
The AASHTO Manual for Bridge Element Inspection provides a comprehensive set of bridge elements, designed to be flexible in nature to satisfy needs of all agencies. This set of elements capture the components necessary for any agency to manage the aspects of the bridge inventory and allows the full utilization of a Bridge Management System (BMS).
There are two different element types included in the element set which are identified as National Bridge Elements (NBEs) or Bridge Management Elements (BMEs). These two element sets combined comprise the full AASHTO element set.
An inspection normally begins with the deck and superstructure elements and proceeds to the substructure. However, there are many factors to be considered when planning a sequence of inspection for a bridge, including:
A sample inspection sequence for a bridge of average length and complexity is presented in Figure 2.1.3. While developing an inspection sequence is important, it is of value only if following it ensures a safe, complete and thorough inspection of the bridge.
1) Roadway Elements
2) Deck Elements
3) Superstructure Elements
4) Substructure Elements
5) Channel and Waterway Elements
Figure 2.1.3 Sample Inspection Sequence
Preparing notes, forms, and sketches prior to the on-site inspection reduces work in the field. Obtain copies of the agency’s standard inspection form for use in recordkeeping and as a checklist to ensure that the condition of all elements is noted.
Create copies of sketches from previous inspection reports so that defects previously documented can simply be updated. Preparing extra copies provides a contingency for sheets that may be lost or damaged in the field.
If previous inspection sketches or design drawings are not available, then pre-made, generic sketches may be used for repetitive features or members. Possible applications of this timesaving method include deck sections, floor systems, bracing members, abutments, piers, and retaining walls. Numbered, pre-made sketches and forms can also provide a quality control check on work completed.
Bridge inspection, like construction and maintenance activities on bridges, often presents motorists with unexpected and unusual situations (see Figure 2.1.4). Most state agencies have adopted the Federal Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD). Some state and local jurisdictions, however, issue their own manuals. When working in an area exposed to traffic, check and follow the governing standards. These standards prescribe the minimum methods for a number of typical applications and the proper use of standard traffic control devices, such as cones, signs, and flashing arrow boards.
Figure 2.1.4 Temporary Traffic Control Operation
Principles and methods, which enhance the safety of motorists and bridge inspectors in work areas, include the following:
Traffic safety is a high priority element on every bridge inspection project where the inspectors' activities are exposed to traffic or likely to affect normal traffic movements.
In addition, schedules may have to be adjusted to accommodate temporary traffic control needs. For example, the number of lanes that can be closed at one time may require conducting the inspection operation with less than optimum efficiency. While it might be most efficient to inspect a floor system from left to right, traffic control may dictate working full length, a few beams at a time. Some agencies require inspections to be performed during low tow traffic (i.e. at night).
The total time required to complete an inspection can vary from what may be documented on a previous inspection report or separately in the bridge file due to the various tasks for completing the inspection. Breaking down and recording the time to complete the various tasks (office preparation, travel, on-site, report preparation) separately benefits future planning and preparation efforts. Break down the inspection time requirements in to office preparation, travel time, field time, and report preparation. The overall condition of the bridge plays a major role in determining how long an inspection takes. Previous inspection reports provide an indication of the bridge's overall condition. It generally takes more time to inspect and document a deteriorated element (e.g., measuring, sketching, and photographing) than it does to simply observe and document that an element is in good condition.
In populated areas, an inspection requiring traffic restrictions may be limited to certain hours of the day, such as 10:00 AM to 2:00 PM. Some days may be banned for inspection work altogether. Actual inspection time may be less than a 40-hour work week in these situations, so adjust the schedules accordingly.
Consider set-up time both before and during the inspection. For example, rigging efforts may require several days before the inspectors arrive on the site. Also, other equipment, such as compressors and cleaning equipment may require daily set-up time. Provide adequate time in the schedule for set-up and take-down time requirements. Also, consider the time to install and remove temporary traffic control devices.
Consider access requirements when preparing for an inspection. Bridge members may be very similar to each other, but they may require different amounts of time to gain access to them. For example, it may take longer to maneuver a lift device to gain access to a floor system near utility lines than for one that is free of obstructions. On some structures, access hatches may need to be opened to gain access to a portion of the bridge.
Adverse weather conditions may not halt an inspection entirely, but may play a significant role in the inspection process. During adverse weather conditions, avoid climbing on the bridge structure. An increased awareness of safety hazards is required, and keeping notes dry can be difficult. During seasons of poor weather, adopt a less aggressive schedule than during the good weather months.
While completing the inspection in a timely and efficient manner, the importance of taking safety precautions cannot be overlooked. Review general safety guidelines for inspection and any agency or bridge specific safety precautions such as for hazardous material and confined space entry. Confined space entry methods are in accordance with OSHA and the owners’ requirements. For climbing inspections, the three basic requirements covered in Topic 2.2.5 for safe climbing are to be followed. For additional information about safety precautions, refer to Topic 2.2.5.
When inspecting a bridge crossing a railroad, obtain an access permit before proceeding with the field inspection. Also obtain a permit when inspecting bridges passing over navigable waterways. Environmental permits and permits to work around endangered species may be required for some bridges and bridge sites.
To perform a complete and accurate inspection, use the proper tools and equipment. Bridge location and type are two main factors in determining required tools and equipment. Refer to Topic 2.4 for a complete list of inspection tools and equipment.
Give consideration to time requirements when special activities are scheduled. These activities may include one or more of the following:
This duty is the on-site work of accessing and examining bridge components and waterway, if present.
Perform inspections in accordance with the National Bridge Inspection Standards (NBIS) and AASHTO Manual for Bridge Evaluation (MBE).
Basic activities include:
Duties associated with the inspection include maintaining the proper structure orientation and member numbering system, and following proper inspection procedures.
The procedures used to inspect a bridge depend largely on the bridge type, the materials used, and the general condition of the bridge. Therefore, be familiar with the basic inspection procedures for a wide variety of bridges.
A first step in the inspection procedure is to establish the orientation of the site and of the bridge. Include the compass directions, the direction of waterway flow, and the direction of the inventory route in the orientation. Also record inspection team members, air temperature, weather conditions, and time.
After the site orientation has been established, the inspector is ready to begin the on-site inspection. Be careful and attentive to the work at hand, and do not overlook any portion of the bridge. Give special attention to those portions that are most critical to the structural integrity of the bridge. (Refer to Topic 6.4 for a description of fracture critical members in steel bridges.)
Combine the prudence used during the inspection with thorough and complete recordkeeping. Careful and attentive observations are to be made, and record every deficiency. A very careful inspection is worth no more than the records kept during that inspection.
Place numbers or letters on the bridge by using crayon or paint to identify and code components and elements of the structure. The purpose of these marks is to keep track of the inspector’s location and to guard against overlooking any portion of the structure.
Note the general approach roadway alignment, and sight along the railing and edge of the deck or girder to detect any misalignment or settlement.
Check the approach pavement for unevenness, settlement, or roughness. Also check the condition of the shoulders, slopes, drainage, and approach guardrail.
Examine the deck and any sidewalks for various deficiencies, noting size, type, extent, and location of each deficiency. Reference the location using the centerline or curb line, the span number, and the distance from a specific pier or joint.
Examine the expansion joints for sufficient clearance and for adequate seal. Record the width of the joint opening at both curb lines, noting the air temperature and the general weather conditions at the time of the inspection.
Finally, check that safety features, signs (load restrictions), and lighting are present, and note their condition.
Inspect the superstructure thoroughly, since the failure of a primary load-carrying member could result in the collapse of the bridge. The primary method of bridge inspection is visual, requiring the removal of dirt, leaves, animal waste, and debris to allow close observation and evaluation of the primary load-carrying members. The most common forms of primary load-carrying members are:
Inspect the bearings thoroughly, since they provide the critical link between the superstructure and the substructure. The primary method of bearing inspection is a visual inspection, which requires removing dirt, leaves, animal waste, and debris to allow close observation and evaluation of the bearings. Record the difference between the rocker tilt and a fixed reference line, noting the direction of tilt, the air or bearing material temperature, and the general weather conditions at the time of the inspection.
The substructure, which supports the superstructure, is made up of abutments, piers, and bents. If “design” or “as-built” plans are available, compare the dimensions of the substructure units with those presented on the plans. Since the primary method of bridge inspection is visual, remove the dirt, leaves, animal waste, and debris to allow close observation and evaluation. Check the substructure units for settlement by sighting along the superstructure and noting any tilting of vertical faces. In conjunction with the scour inspection of the waterway, check the substructure units for undermining, noting both its extent and location.
Inspect culverts regularly to identify any potential safety problems and maintenance needs. Examine the culvert for various deficiencies, noting size, type, extent, and location of each deficiency. Reference the location using the centerline. In addition to the inspection of the culvert and its components, look for high-water marks, changes in drainage area, scour, and settlement of the roadway.
Waterways are dynamic in nature, with their volume of flow and their path continually changing. Therefore, carefully inspect bridges passing over waterways for the effects of these changes.
Maintain a historical record of the channel profile and cross-sections. Record and compare current measures to initial (base line) measures, noting any meandering of the channel both upstream and downstream. Report any skew or improper location of the piers or abutments relative to the stream flow.
Scour is the removal of material from the streambed or streambank as a result of the erosive action of streamflow. Scour is the primary concern when evaluating the effects of waterways on bridges (see Figure 2.1.5). Determine the existence and extent of scour using a grid system and noting the depth of the channel bottom at each grid point.
Figure 2.1.5 Inspection for Scour and Undermining
Note the embankment erosion both upstream and downstream of the bridge, as well as any debris and excessive vegetation. Record their type, size, extent, and location. Note also the high water mark, referencing it to a fixed elevation such as the bottom of the superstructure.
There are several general terms used to describe bridge deficiencies:
Refer to Chapter 6 for a more detailed list and description of types and causes of deterioration for specific materials. As described in Chapter 6, each material is subject to unique deficiencies. Therefore, be familiar with the different inspection methods used with each material.
When inspecting timber structures, determine the extent and severity of decay, weathering and wear, being specific about dimensions, depths, and locations. Sound and probe the timber to detect hidden deterioration due to decay, insects, or marine borers.
Note any large cracks, splits, or crushed areas. While collision or overload damage may cause these deficiencies, avoid speculation as to the cause and be factual. Note any fire damage, recording the measurements of the remaining sound material. Document any exposed untreated portions of the wood, indicating the type, size, and location.
When inspecting concrete structures, note all visible cracks, recording their type, width, length, and location. Also record any rust or efflorescence stains. Concrete scaling can occur on any exposed face of the concrete surface, so record its area, location, depth, and general characteristics. Inspect concrete surfaces for delamination or hollow zones, which are areas of incipient spalling, using a hammer or a chain drag. Carefully document any delamination using sketches showing the location and pertinent dimensions.
Unlike delamination, spalling is readily visible. Document any spalling using sketches or photos, noting the depth of the spalling, the presence of exposed reinforcing steel, and any deterioration or section loss that may be present on the exposed reinforcement.
When inspecting metal structures, determine the extent and severity of corrosion, carefully measuring the amount of cross section remaining. Note all cracks, recording their length, size, and location. Document all bent or damaged members, noting the type of damage and amount of deflection.
Loose rivets or bolts can be detected by striking them with a hammer while holding a thumb on the opposite end of the rivet or bolt. Movement can be felt if it is loose. In addition, note any missing rivets or bolts.
Note any frozen pins, hangers, or expansion devices. One indication of this is if the hangers or expansion rockers are inclined or rotated in a direction opposite to that expected for the current temperature. In cold weather, rocker bearings lean towards the fixed end of the bridge, while in hot weather, they lean away from the fixed end. A locked bearing is generally caused by heavy rust on the bearing elements.
For the evaluation to be substantiated, document and record all inspection findings. Documentation is referred to as the “condition remarks” on the inspection form or in the inspection report.
The examination of stone masonry and mortar is similar to that of concrete. Carefully inspect the joints for cracks and other forms of mortar deterioration. Inspection techniques are generally the same as for concrete.
Check masonry arches or masonry-faced concrete arches for mortar cracks, vegetation, water seepage through cracks, loose or missing stones or blocks, weathering, and spalled or split blocks and stones.
When inspecting Fiber Reinforced Polymers (FRP), note any blistering, voids and delaminations, discoloration, wrinkling, fiber exposure and any scratches. Document all visible cracks, recording their width, length, and location.
Critical findings are any structural or safety-related deficiency that requires immediate follow-up inspection or action. When a critical finding is discovered, immediately communicate and document the critical finding according to agency procedures.
Refer to Topic 4.5 for a detailed description of critical findings and the methods required to address any critical findings discovered.
Documentation is essential for any type of inspection. Gather enough information to ensure a comprehensive and complete report. Report preparation is a duty, which reflects the effort that the inspector puts in to performing the inspection. Both documentation and preparation are to be comprehensive. The report is a record of both the bridge condition and the inspector's work.
Basic activities in preparing the inspection report include:
A sample bridge inspection report can be found in Appendix B of this manual. Follow the procedures of the agency responsible for the bridge.
Another common duty is to identify work recommendations for bridge preservation and follow-up to critical findings. Recommend work items that promote public safety and maximize useful bridge life. Refer to Topic 4.5 for details on follow-up to critical findings.
Work recommendations are commonly aligned with an agency’s bridge preservation program and are included in preservation work plans. These work recommendations are condition driven or cyclical. Examples of preservation activities include: deck or bridge washing, flushing the scuppers and down spouts, lubricating the bearings and painting the structure.
Carefully consider the benefits to be derived from completing the work recommendation and the consequences if the work is not completed. Also, check the previous report recommendations to see what work was recommended and the priority of such items. If work was scheduled to be completed before the next inspection, note if the work was completed and the need for any follow-up work.
The NBIS regulation requires the establishment of a statewide or Federal agency wide procedure to assure that critical finds are addressed in a timely manner. Additionally, the NBIS requires that FHWA be periodically notified of actions taken to resolve or monitor critical findings. The duty of the inspection team is to follow statewide or Federal agency-wide procedures for the follow-up on critical findings. It is the responsibility of Bridge Owners to implement procedures for addressing critical deficiencies, including:
Critical findings are presented in detail in Topic 4.5.
The type of inspection may vary over the useful life of a bridge to reflect the intensity of inspection required at the time of inspection. The seven types of inspections identified in the AASHTO Manual for Bridge Evaluation are described below and allow a Bridge Owner to establish appropriate inspection levels consistent with the inspection frequency and the type of structure and details.
An initial inspection is the first inspection of a bridge as it becomes a part of a bridge file, but the elements of an initial inspection may also apply when there has been a change in configuration of the structure (e.g., widening, lengthening, supplemental bents, etc.) or a change in bridge ownership. The initial inspection is a fully documented investigation and is accompanied by load capacity ratings. The purpose of this inspection is two-fold. First, an initial inspection provides all Structure Inventory and Appraisal (SI&A) data. Second, it provides baseline structural conditions and identification of existing problems.
Routine inspections are regularly scheduled inspections consisting of observations and/or measurements needed to determine the physical and functional condition of the bridge, to identify any changes from “initial” or previously recorded conditions, and to ensure that the structure continues to satisfy present service conditions. Inspection of underwater portions of the substructure is limited to observations during low-flow periods and/or probing for signs of scour and undermining. The areas of the structure to be closely monitored are those determined by previous inspections and/or load rating calculations to be critical to load-carrying capacity. Follow the plan of action for scour critical bridges.
According to the NBIS, inspect each bridge at regular intervals not to exceed 24 months. However, certain bridges require inspection at less than the 24-month interval. Establish criteria to determine inspection frequency and intensity based on such factors as age, traffic characteristics, and known deficiencies. Certain bridges may be inspected at greater than 24-month intervals, not to exceed 48 months, with prior FHWA-approval. This may be appropriate when past inspection findings and analysis justifies the increased inspection interval.
A damage inspection is an unscheduled inspection to assess structural damage resulting from environmental factors or human actions. The scope of inspection is sufficient to determine the need for emergency load restrictions or closure of the bridge to traffic and to assess the level of effort necessary for an effective repair.
An in-depth inspection is a close-up, inspection of one or more members above or below the water level to identify any deficiencies not readily detectable using routine inspection procedures. Hands-on inspection may be necessary at some locations. When appropriate or necessary to fully ascertain the existence of or the extent of any deficiencies, nondestructive field tests may need to be performed. The inspection may include a load rating to assess the residual capacity of the member or members, depending on the extent of the deterioration or damage. This type of inspection can be scheduled independently of a routine inspection, though generally at a longer interval, or it may be a follow-up for other inspection types. For small bridges, the in-depth inspection includes all critical members of the structure. For large and complex structures, these inspections may be scheduled separately for defined segments of the bridge or for designated groups of elements, connections, or details.
According to the NBIS, establish criteria to determine the level and frequency of this type of inspection.
A fracture critical member (FCM) inspection is performed within arm's length of steel members in tension, or with a tension element, who failure would probably cause a portion of or the entire bridge to collapse. The FCM inspection uses visual methods that may be supplemented by nondestructive testing. A very detailed visual hands-on inspection is the primary method of detecting cracks. This may require that critical areas be specially cleaned prior to the inspection and additional lighting and magnification be used. Other nondestructive methods may be used at the discretion of the Bridge Owner. Where the fracture toughness of the steel is not documented, some tests may be necessary to determine the threat of brittle fracture at low temperatures.
According to the NBIS, fracture critical members (FCMs) are to be inspected at regular intervals not to exceed 24 months. However, certain FCMs require inspection at less than 24-month intervals. Establish criteria to determine the inspection level and frequency to which these members are inspected considering such factors as age, traffic characteristics, and known deficiencies.
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, generally requiring diving or other appropriate procedures. Underwater inspections are an integral part of a total bridge inspection plan. Scour evaluations are conducted for all bridges over water. Determine the severity and extent of scour, immediately communicating and documenting critical findings. Follow the plan of action for scour critical bridges.
Structural damage, scour and erosion due to water movement, drift, streambed load, ice loading, navigation traffic collision, and deleterious effects of water movement or of elements, are typical occurrences that could result in the decision to conduct underwater inspections at shorter intervals.
According to the NBIS, underwater structural elements are inspected at regular intervals not to exceed 60 months. However, certain underwater structural elements require inspection at less than the 60-month intervals. Establish criteria to determine the level and frequency to which these members are inspected considering such factors as construction material, environment, age, scour characteristics, condition rating from past inspections and known deficiencies. Certain underwater structural elements may be inspected at greater than 60-month intervals, not to exceed 72 months, with written FHWA-approval. This may be appropriate when past inspection findings and analysis justifies the increased inspection interval.
A special inspection is an inspection scheduled at the discretion of the Bridge Owner. It is used to monitor a particular known or suspected deficiency, such as foundation settlement or scour, fatigue damage, or the public’s use of a load posted bridge. These inspections are not usually comprehensive enough to meet NBIS requirements for routine inspections.
According to the NBIS, establish criteria to determine the level and frequency of this type of inspection. Guidelines and procedures on what to observe and/or measure are provided, and a timely process to interpret the field results is in place.
While completing the inspection in a timely and efficient manner is important, safety is also a major concern in the field. Bridge inspection is inherently dangerous and therefore requires continual watchfulness on the part of each member of the inspection team. Attitude, alertness, and common sense are three important factors in maintaining safety. To reduce the possibility of accidents, bridge inspectors need to be concerned about safety.
Five key motivations for bridge inspection safety:
Constantly be aware of safety concerns. Spending the effort to be safe pays big dividends in avoided expenses and grief.
The employer is responsible for providing a safe working environment, including:
The supervisor is responsible for maintaining a safe working environment, including:
Bridge inspectors are ultimately responsible for their own safety. The bridge inspector's responsibilities include:
It is important to dress properly for the job. Be sure to wear field clothes that are properly sized and appropriate for the climate. For general inspection activities, wear boots with traction lug soles. For climbing of bridge components, wear boots with a steel shank (with non-slip soles without heavy lugs), as well as gloves. Wearing a tool pouch enables the inspector to carry tools and notes with hands free for climbing and other inspection activities.
Safety equipment is designed to prevent injury. Use the equipment correctly in order for it to provide protection. The following are some common pieces of safety equipment:
A hard hat can prevent serious head injuries in two ways. First, it provides protection against falling objects. The bridge site environment during inspection activities is prone to falling objects. Main concerns are:
Secondly, a hard hat protects the inspector’s head from accidental impact with bridge components. When inspections involve climbing or access equipment, the inspector is frequently dodging various configurations of superstructure elements. These superstructure elements can be sharp edged and are always unyielding. If the inspector makes a mistake in judgement during a maneuver and impacts the structure, a hard hat may prevent serious injury.
It is a good practice to always wear a hard hat (see Figure 2.2.1). Also, if the inspector is free climbing, it is a good practice to wear a chinstrap with the hard hat.
Figure 2.2.1 Inspector Wearing a Hard Hat
When performing activities near traffic, the inspector is required to wear a safety vest. Be sure the vest conforms to current OSHA and MUTCD standards. The combination of bright color and reflectivity makes the inspector more visible to passing motorists. Safety is improved when the motorist is aware of the inspector’s presence (see Figure 2.2.2).
Figure 2.2.2 Inspector Wearing a Reflective Safety Vest
Eye protection is necessary when the inspector is exposed to flying particles. Glasses with shatterproof lenses are not adequate if side protection is not provided. It is also important to note that only single lens glasses be worn when climbing (no bifocals).
Wear eye protection during activities such as:
Although one may not immediately think of gloves as a piece of safety equipment, they can prove to be an important safety feature. Wearing gloves protect the inspector’s hands from harmful effects of deteriorated members (see Figure 2.2.3). In many inspections, structural members have been deteriorated to the point where the edges of the members have become razor sharp. These edges can cause severe cuts and lacerations to the inspector’s hands that may become infected.
Figure 2.2.3 Inspector Wearing Safety Goggles and Gloves
Always wear a life jacket when working over water or in a boat (see Figure 2.2.4). If an accident occurs, good swimmers may drown if burdened with inspection equipment. Also, if knocked unconscious or injured due to a fall, a life jacket keeps the inspector afloat. Also wear a life jacket when wearing hip or chest waders. If an inspector slips or steps in an area that is too deep, their waders can fill with water and drag them under, making swimming impossible.
Figure 2.2.4 Inspector Wearing a Life Jacket
A respirator or dust mask can protect the inspector from harmful airborne contaminants and pollutants (see Figure 2.2.5). Consult agency or OSHA regulations for approved types and appropriate usage.
Conditions requiring a respirator include:
Figure 2.2.5 Inspector Wearing a Respirator
The safety harness and lanyard is the inspector’s lifeline in the event of a fall (see Figure 2.2.6). Use this equipment as required by conditions. Make sure you satisfy agency and OSHA requirements.
For example, some agencies require a safety harness be worn in the following situations:
Figure 2.2.6 Inspector with Safety Harness with a Lanyard
To reduce the possibility of injury, the maximum lanyard length limits a fall to 6 feet per OSHA regulations. Further protection can be achieved using a shock absorber between the lanyard and the safety harness. The shock absorber reduces g-forces through the controlled extension of nylon webbing, which is pre-folded and sewn together. Two lanyards are required with one lanyard being tied off to a solid structural member or to a safety line rigged always for this purpose. Use the second lanyard to allow safe movement around obstacles connecting the second lanyard before disconnecting the first lanyard in order to safely move along the structure.
Do not tie off to scaffolding or its supporting cable. One of the reasons for tying off is to limit your fall in case the rigging or scaffold fails. When working from a under bridge inspection vehicle or bucket truck, tie off to the structure if possible. Exercise extreme caution not to allow the equipment to be moved out from under someone tied to the bridge. If the machine is being moved frequently, it is best to tie off to the bucket or boom.
When an inspection takes place suspended over water and a drowning hazard exists that cannot be mitigated by other means such fall protection, a safe work environment typically requires a personal flotation device and some sort of rescue capability such as a manned boat/skiff or other means such as a designated rescue person present. In the event of an accident in which someone was to fall into the water, the boat or designated rescue person can assist them quickly. This is especially important if the individual has been rendered unconscious.
Accidents are usually caused by human error or equipment failure. Part of safety awareness is acknowledging this and planning ahead to minimize the effects of those errors or failures.
Accidents caused by equipment failure can often be traced to inadequate or improper maintenance. Inspection, maintenance, and update of equipment can minimize failures. Accidents caused by people are usually caused by an error in judgment, thoughtlessness, or trying to take shortcuts.
Specific causes of accidents include the following:
Safety precautions can be divided in to several categories: General Precautions, Climbing Safety, Confined Spaces, Vegetation, Night Work, Working Around Water, and Culverts.
The inspector has to be mentally prepared to do a climbing inspection. A good safety attitude is of foremost importance. Address the following three precautions:
Some general guidelines for safe inspections are as follows:
Work in pairs. Do not take any action without someone else there to help in case of an accident. Make sure someone else knows where you are. If someone seems to be missing, locate that person immediately.
First Aid Training is recommended for bridge inspectors and is available through organizations such as OSHA or the American Red Cross.
If an inspector is injured during an inspection, it is important to know First Aid and/or cardiopulmonary resuscitation (CPR). The American Red Cross offers training for First Aid, CPR and AED (automatic external defibrillator). Local fire departments and the American Heart Association (AHA) can also provide training for CPR.
There are two primary areas of preparation necessary for a safe climbing inspection:
Figure 2.2.7 Inspection Involving Extensive Climbing
Organization of the Inspection - A good inspection procedure incorporates a climbing strategy that minimizes climbing time. For example, beginning the day with an inspection of a truss span from one bent and finishing at the next bent by lunch time eliminates unproductive climbing across the span.
The inspection procedure needs to have an inspection plan so the inspection team knows where to go, what to do, and what tools are needed to perform the inspection. An organized inspection reduces the chance of the inspectors falling or getting stuck in a position in which they are unable to get down.
Weather conditions are a primary consideration when organizing a climbing inspection. Moderate temperatures and a sunny day are desirable.
Rain conditions warrant postponement of steel bridge inspections, as wet steel is extremely slippery.
After a rainy day, be sure that your boots are free of mud, and use extreme caution in areas where debris accumulation may cause a slippery surface.
The inspection team needs to be well equipped to properly complete their inspection.
Check personal attire for suitability to the job:
Check inspection equipment for proper use and condition.
Accidents involving ladders are the most common type of inspection-related accident. Refer to and follow OSHA for rules applicable to stairways and ladders.
In order to use a ladder properly, consider the following:
Figure 2.2.8 Proper Use of Ladder
Refer to and follow OSHA for rules applicable to scaffolding. Check scaffolding for the height and load capacity necessary to support the inspection team.
Load tests can be performed on the ground with planned equipment and personnel. Perform a daily inspection for cracks, loose connections, and buckled or weak areas prior to use.
Never use single planks. Use two or more planks securely cleated together. Securely attach plank ends to their supports. Inspect planks for knots, splits, cracks, and deterioration prior to use.
Use of platform trucks, bucket trucks, and underbridge inspection vehicles may be necessary to access elements during an inspection (see Figure 2.2.9). Confirm that they are in safe operating condition. Only use such equipment when placed on a firm surface at a slope not exceeding the manufacturer’s recommendations. Use extreme caution when operating near traffic.
Permanent inspection access devices are ideal. However, be on guard for misalignment and deterioration of elements, such as flooring, hand-hold rods, and cables (see Figure 2.2.10).
Figure 2.2.10 Inspection Catwalk
Be familiar with proper rigging techniques. The support cables need to be at least one-half inch in diameter. The working platform or "stage" need to be at least 20 inches wide. Use a line or tie-off cable separate from the primary rigging.
Use common sense with regard to rigging. Do not blindly trust the people arranging the rigging. Mistakes by riggers can cause life threatening accidents. If a method is unsafe or doubtful, question it and get it changed if necessary. Do not rely on ropes or planks left on the bridge by prior work. They may be rotted or not properly attached.
Figure 2.2.11 Inspection Rigging
Inspection of box girder bridges, steel box pier caps, steel arch rings, arch ties, cellular concrete structures, and long culverts is often categorized as confined spaces. Confined space entry is regulated by Occupational Safety and Health Administration (OSHA) and requires proper training, equipment, and permitting.
There are four major concerns when inspecting a confined space:
When inspecting a confined area, use the safety standards prescribed by OSHA and any additional agency or employer requirements. The following is a general description of the basic requirements. Refer to OSHA for specifics.
Pre-entry air tests:
Mechanical ventilation:
Basic safety procedures:
Be aware of any vegetation located around any substructures. Poison ivy, oak and sumac are examples of vegetation which can cause skin irritations if touched by someone. Also, it is important to be aware of any tall vegetation which could hide holes in the ground and lead to possible injury if not found. Tall vegetation can also hide other tripping hazards.
When working at night, it is important to be properly dressed. This is necessary so the inspectors can be more visible by passing motorists. It can be accomplished by wearing a safety vest which has both bright colors and reflectivity. The use of proper temporary traffic control also helps motorists be aware that there are workers ahead.
When wading in water, it is important to be aware of any scour holes and be careful not slip or fall on objects in the water. If an inspector slips or steps into a scour hole, their waders can fill with water and drag them under, making swimming impossible. It is also important to wear a life vest while wading to help prevent the inspector from being pulled down if the waders were to fill up with water. It is beneficial for the inspector to carry and use probing rod to locate scour holes and soft stream bed material. Be mindful of potentially dangerous aquatic life.
Extensive streambed scour may result in channel depressions. During periods of low flow the depth of water in these holes may be significantly greater than the remainder of the streambed. This could give the inspector the impression that wading is safe. It is advisable that the inspector use a probing rod to check water depth wherever he/she plans to walk.
Storms may generate high flows in culverts very quickly. This creates a dangerous situation for the inspectors. It is not uncommon for culverts to carry peak flow long before a storm reaches the culvert site. Be cautious whenever storms appear imminent.
When performing an underwater inspection, particularly in low visibility and/or high current situations, use extreme care and be sure to watch for drift and debris at any height in the water. See Topic 13.3.2, for additional safety concerns.
There are several hazards that can be encountered when performing a culvert inspection. Being aware of these situations and exercising proper precautions protect the inspector from these dangerous and potentially life threatening hazards. The following are some of the hazardous conditions an inspector may encounter.
Culverts with inadequate ventilation can develop low oxygen levels or high concentrations of toxic and/or explosive gases. This is a big concern when one culvert end may be blocked or inspection is being performed on a long culvert.
If air quality is suspect, perform tests to determine the concentration of gases. Testing devices may be as simple as badges worn by inspectors that change colors when in the presence of a particular gas. Devices may also be sophisticated instruments that measure the concentration of several gases.
Observe confined space entry requirements when inspecting a long culvert or any culvert with restricted ventilation.
Quicksand conditions can occur in sandy streambeds, especially at the outlet end of the culvert. Be aware of these conditions and proceed with caution in geographical areas known to have these problems.
Do not obstruct traffic during bad weather. Avoid the inspection of the top of concrete decks during or just after it rains (see Figure 2.2.12).
Figure 2.2.12 Inclement Weather Causing Slippery Bridge Members and Poor Visibility for Motorists
Bridge inspection usually only requires traffic control procedures for a relatively short term closure Long term closures for construction activity which use concrete barriers are not included in this topic.
Figure 2.3.1 Temporary Traffic Control Operation
Bridge inspection, like construction and maintenance activities on bridges, often presents motorists with unexpected and unusual situations. Most state agencies have adopted the Federal Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD). Some states and local jurisdictions, however, issue their own standard manuals or drawings.
When working in an area exposed to traffic, check and follow the existing agency standards. These standards prescribe the minimum procedures for a number of typical applications and the proper use of standard temporary traffic control devices such as cones, signs, and flashing arrow-boards (see Figure 2.3.1). Sometimes after initial installation, temporary traffic control may need revised to provide adequate protection to motorists, pedestrians or inspectors.
Temporary traffic control devices used on street and highway construction or maintenance work need to conform to the applicable standards of the MUTCD and the agency.
Minimize inspection time to reduce exposure to potential hazards without compromising the thoroughness of the inspection. Principles and procedures which have been shown to enhance the safety of motorists, pedestrians, and bridge inspectors in the vicinity of work areas include the following:
Traffic safety in work zones is an integral and high priority element of every inspection project, from the planning stage to performance of the inspection. Keep in mind the safety of the motorist, pedestrian, and worker.
The basic safety principles governing the design of temporary traffic control for roadways and roadsides, govern the design of inspection sites. The goal is to route traffic through such areas with geometrics and temporary traffic control devices comparable to those for normal highway situations. Clearly communicate to the driver the notice of work site locations and guidance through these sites.
A temporary traffic control plan, in detail appropriate to the complexity of the work project, is prepared and understood by the responsible parties before the site is occupied. The official trained in safe traffic control practices approves any changes in the temporary traffic control plan.
Inhibit traffic movement as little as practical. Design temporary traffic control in work sites on the assumption that motorists only reduce their speeds if they clearly perceive a need to do so. Avoid reducing the speed zoning as much as practical.
The objective is a traffic control plan that uses a variety of temporary traffic control measures and devices in whatever combination necessary to assure smooth, safe vehicular movement past the work area and at the same time provide safety for the equipment and the workers on the job. Avoid frequent and abrupt changes in geometrics, such as lane narrowing, dropped lanes, or main roadway transitions that require rapid maneuvers.
Make provisions for the safe operation of work vehicles, particularly on high speed, high volume roadways. This includes the use of roof mounted flashing lights or flashers when entering or leaving the work zone. This also includes considering the number of lanes that can be closed at one time for an operation. While it might be most cost efficient to inspect the entire floor system from left to right, temporary traffic control may dictate working partial width, a few stringers at a time.
A good traffic control plan provides safe and efficient movement of motorists and pedestrians and the protection of bridge inspectors at work areas.
Provide adequate warning, delineation, and channelization to assure the motorist positive guidance in advance of and through the work area. Use proper signing and other devices which are effective under varying conditions of light and weather.
The maintenance of roadside safety requires constant attention during the life of the work because of the potential increase in hazards. Remove temporary traffic control devices immediately when no longer needed.
To accommodate run-off-the-road incidents, disabled vehicles or other emergency situations, it is desirable to provide an unencumbered roadside recovery area that is as wide as practical.
Accomplish the channelization of traffic by the use of cones, barricades, and other lightweight devices which yield when hit by errant vehicles.
Store equipment and materials in such a manner as not to be vulnerable to run-off-the-road vehicle impact, whenever practical. Also, provide adequate attenuation devices when safe storage is not available.
Traffic represents as great, or even greater, threat to the inspector’s safety than climbing high bridges. The work zone is intended to be a safe haven from traffic so the inspectors can concentrate on doing their jobs.
As such, the work zone needs to be clearly marked so as to guide the motorist around it and, insofar as possible, prevent errant vehicles from entering (see Figure 2.3.2). To minimize traffic disruption, the work zone needs to be as compact as possible, but wide enough and long enough to permit access to the area to be inspected and allow for safe movement of workers and equipment. The end of the work zone is to be clearly signed as a courtesy to the motorist.
Inspection vehicles and equipment need to be made visible to the motorists with flashing marker lights or arrow boards as appropriate (see Figure 2.3.3).
Use roof mounted flashing lights or flashers on vehicles entering and exiting the work zone to distinguish them from other motorists’ vehicles. Also, vehicles are to use extreme caution when moving in and out of the work zone. Allow motorists ample time to react to the vehicle's movements.
Figure 2.3.3 Inspection Vehicles with Flashing Light
Individuals in a work zone are to wear approved safety vests and hard hats for visibility and identification. They also help make the inspector look “official” to the public. Also, it is important for the inspector to stay within the work zone for their own safety.
Each bridge inspection project is different and has traffic concerns that are unique to that location. Selection of the proper temporary traffic control devices for each location is dependent upon many factors. Though there are several different types of temporary traffic control devices, there are some basic principles for efficient temporary traffic control devices:
Advance warning is essential to get the right response from drivers. The MUTCD provides guidance on the positioning of advance warning signs for specific traffic control applications.
These basic principles for temporary traffic control devices have been factored into the various agencies’ procedures for work area traffic control. These procedures represent efforts by trained people. Do not change traffic patterns without consulting the MUTCD, agency standards or traffic control personnel.
Types of temporary traffic control signs include the following:
Figure 2.3.6 Examples of Guide Signs
Figure 2.3.8 Changeable Message Sign
The functions of channelizing devices are to warn and alert drivers of hazards created by construction or maintenance activities in or near the traveled way and to guide and direct drivers safely past the hazards.
Devices used for channelization provide a smooth and gradual transition in moving traffic from one lane to another, onto a bypass or detour, or in reducing the width of the traveled way. They need to be constructed so as not to inflict any undue damage to a vehicle that inadvertently strikes them.
Channelizing devices are elements in a total system of traffic control devices for use in highway construction and maintenance operations. These elements are preceded by a subsystem of warning devices that are adequate in size, number, and placement for the type of highway on which the work is to take place.
Typical channelizing devices include the following:
Figure 2.3.13 Temporary Traffic Barriers
Another type of control device is lighting. Lighting devices are used to supplement retroreflectorized signs, barriers, and channelizing devices. Examples of lighting include the following:
A number of hand signalizing devices, such as STOP/SLOW paddles, flashing lights, flashlights, and red flags, are used to control traffic through work zones. The sign paddle bearing the clear messages “STOP” or “SLOW” provides motorists with more positive guidance than flags and is generally the primary hand signaling device. If permitted by the agency, limit flag use to emergency situations and at spot locations that can best be controlled by a single flagger.
Since flaggers are responsible for human safety and make the greatest number of public contacts of any inspection personnel, it is important that qualified personnel be selected. The following are qualifications for a flagger:
For daytime and nighttime activity, flaggers shall wear high-visibility safety apparel that meets Performance Class 2 or 3 requirements of the ANSI/ISEA 107-2004 publication titled American National Standard for High-Visibility Apparel and Headwear. The apparel background (outer) material shall be fluorescent orange-red, fluorescent yellow-green, or a combination of the two as defined in the ANSI standard. The retroreflective material shall be orange, yellow, white, silver, yellow-green, or a fluorescent version of these colors, and shall be visible at a minimum distance of 1,000 feet. The retroreflective safety apparel shall be designed to clearly identify the wearer as a person.
For nighttime activity, high-visibility safety apparel that meets the Performance Class 3 requirements of the ANSI/ISEA 107-2004 publication should be considered for flagger wear.
Flaggers are provided at work sites to stop traffic intermittently as necessitated by work progress. They also maintain continuous traffic past a work site at reduced speeds to help protect the work crew. For both of these functions, the flagger is always clearly visible to approaching traffic for a distance sufficient to permit proper response by the motorist to the flagging instructions and to permit traffic to reduce speed before entering the work site. In positioning flaggers, consideration is given to maintaining color contrast between the work area background and the flagger’s protective garments.
Figure 2.3.15 Use of Hand Signaling Devices by Flagger (from Manual on Uniform Traffic Control Devices (MUTCD))
Use the following methods of signaling with sign paddles (see Figure 2.3.15):
Use the following methods of signaling with a flag (see Figure 2.3.15):
Figure 2.3.16 Stopping Sight Distance as a Function of Speed (from Manual on Uniform Traffic Control Devices (MUTCD))
The flaggers stand either on the shoulder adjacent to the traffic being controlled or in the barricaded lane (see Figure 2.3.17). At a spot obstruction, a position may have to be taken on the shoulder opposite the barricaded section to operate effectively. Under no circumstances is a flagger to stand in the lane being used by moving traffic. The flagger always is clearly visible to approaching traffic. For this reason, the flagger has to stand alone, never permitting a group of workers to congregate around the flagger station. The flagger is stationed sufficiently in advance of the work force to warn them of approaching danger, such as out-of-control vehicles.
Figure 2.3.17 Flagger with Stop/Slow Paddle
Adequately protect flagger stations and precede them by proper advance warning signs. At night, adequately illuminate flagger stations.
At short lane closures where adequate sight distance is available for the safe handling of traffic, the use of one flagger may be sufficient.
Where traffic in both directions use a single lane for a limited distance, make provisions for alternate one-way movement to pass traffic through the constricted work zone. At a spot obstruction, such as a short bridge, the movement may be self-regulating. However, where the one-lane section is of any length, there needs to be some means of coordinating movements at each end so that vehicles are not simultaneously moving in opposite directions in the work zone and so that delays are not excessive at either end. Chose control points at each end of the route so as to permit easy passing of opposing lines of vehicles.
Alternate one-lane, two-way temporary traffic control may be facilitated by the following means:
Flagger control is usually used for bridge inspection, where the one-lane section is short enough so that each end is visible from the other end. Traffic may be controlled by means of a flagger at each end of the section. Designate one of the two as the chief flagger to coordinate movement. They are able to communicate with each other verbally or by means of signals. These signals are not such as to be mistaken for flagging signals.
Where the end of a one-lane, two-way section is not visible from the other end, the flaggers may maintain contact by means of radio or cell telephones. So that a flagger may know when to allow traffic to proceed into the section, the last vehicle from the opposite direction can be identified by description or license.
Shadow Vehicles with truck mounted attenuators (TMAs) are used to prevent vehicles from entering the work zone if the motorist drifts into the lane closure. Each agency has its own specific requirements, but a shadow vehicle is generally employed any time a shoulder or travel lane is occupied by workers or equipment. Shadow vehicles are equipped with appropriate lights and warning signs which may be used for stationary operations for additional protection of occupants and vehicles within the work zone.
Figure 2.3.18 Shadow Vehicle with Attenuator
On some inspection projects, police assistance may be helpful and even required. The presence of a patrol car aids in slowing and controlling the motorists. At a signalized intersection near a job site, a police officer may be required to ensure traffic flows properly and smoothly.
Some states have specialized traffic crews for high traffic roads. They are used due to their specialized training, allowing for a safer work environment.
Since the fundamental goal of bridge inspection is to enhance public safety, it makes little sense to endanger that same public by inadequate traffic control measures. Temporary traffic control does take time, money, and effort. It is, however, a necessary part of the business of bridge inspection.
In the broadest sense, the motorist is the customer of everyone in the transportation industry. Like everyone else, bridge inspectors need to treat customers well by inconveniencing them as little as possible and protecting their safety. This means providing well thought out, clear, and effective traffic control measures.
Also consider pedestrians. If a walkway is to be closed, be sure it is properly signed and barricaded. Indicate an alternate route for the pedestrian, if necessary through or preferably around the work zone.
Each person whose actions affect inspection, maintenance and construction zone safety (from the upper-level management personnel to construction and maintenance field personnel) need training appropriate to the job decisions each individual is required to make. Only those individuals who are qualified by means of adequate training in safe traffic control practices and have a basic understanding of the principles established by applicable guidelines and regulations supervise the selection, placement, and maintenance of temporary traffic control devices in bridge safety inspection, maintenance, and construction areas.
Legally and morally, it is the inspector’s responsibility to follow the regulations and guidelines of the agency having jurisdiction.
The primary goal of good traffic control is safety - safety of the workers, motorists, and pedestrians. If there is an accident, the secondary goal is to be able to defend yourself and your employer. Accidents bring lawsuits. Lawsuits bring inquiries about who is responsible. Temporary traffic control is one thing that is investigated. Anything not done in accordance with published standards, regulations, and directives could bring blame upon whoever violated them. Being blamed for an accident is expensive and damaging.
Several factors play a role in what type of equipment is needed for an inspection. Bridge location and type are two of the main factors in determining equipment needs. If the bridge is located over water, certain pieces of equipment such as life jackets and boats are necessary to have. Also, if the bridge is made of timber, then specific pieces of equipment like timber boring tools and ice picks are needed, whereas they are not necessary on a steel or concrete bridge. Another factor influencing equipment needs is the type of inspection. It is therefore important to review every facet about the bridge before beginning an inspection. A few minutes spent reviewing the bridge files and making a list of the necessary equipment can save hours of wasted inspection time in the field if the inspectors do not have the required equipment.
In order for the inspector to perform an accurate and comprehensive inspection, the proper tools are to be used. Standard tools that an inspector uses at the bridge site can be grouped into seven basic categories:
Figure 2.4.1 Tools for Cleaning
Figure 2.4.2 Tools for Inspection
Figure 2.4.3 Tools for Visual Aid
Figure 2.4.4 Tools for Measuring
Tools for cleaning include:
Tools for inspection include:
Tools for visual aid include:
Tools for measuring include:
Tools for documentation include:
Some common tools for access include:
Tools for access are described in further detail in Topic 2.5.2.
Miscellaneous equipment includes:
For the routine inspection of a common bridge, special equipment is usually not necessary. However, with some structures, special inspection activities require special tools. These special activities are often subcontracted by the agency responsible for the bridge. These inspectors are familiar with the special equipment and its application.
Special circumstances may require the use of a transit, a level, an incremental rod, or other survey equipment. This equipment can be used to establish a component's exact location relative to other components, as well as an established reference point.
Non-destructive evaluation (NDE) is the in-place examination of a material for structural integrity without damaging the material. NDE equipment allows the inspector to "see" inside a bridge member and assess deficiencies that may not be visible with the naked eye. Generally, a trained technician is necessary to conduct NDE and interpret their results. For a more detailed description of NDE, refer to Topics 15.1.2, 15.2.2, and 15.3.2.
Underwater inspection is the examination of substructure units and the channel below the water line. When the waterway is shallow, underwater inspection can be performed above water with a simple probe. Probing can be performed using a range pole, piece of reinforcing steel, a survey rod, a folding rule, or even a tree limb.
When the waterway is deep, an underwater inspection is performed by trained divers. This requires special diving equipment that includes a working platform, fathometer, air supply systems, radio communication, and sounding equipment. Refer to Topic 13.3 for a more detailed description of underwater inspection equipment.
An inspection may require special equipment to prepare the bridge prior to the inspection. Such special equipment includes:
In addition to the standard and special equipment listed previously, there are new equipment and technology available to aid in bridge inspection. The developments in various types of advanced testing methods are described in Topics 15.1, 15.2 and 15.3. The following information represents some of the advances in inspection tools and data collection.
Rotary percussion is a method whereby a uniform tapping is produced by rolling a gear-toothed wheel on a concrete member to detect the presence of concrete deficiencies. This allows for the inspection of overhead and vertical surfaces to be done quickly, and is similar to using a chain drag for the inspection of horizontal surfaces. Advantages of rotary percussion testing tools include the ability to detect near-surface delaminations, quickness of testing, low equipment cost, relatively low level of user’s skill required, and low sensitivity to the surroundings.
Figure 2.4.5 Rotary Percussion
There is a specialized device used to measure the depth of scour during flood flows. It consists of a depth finder mounted on a water ski. The use of a water ski allows for depth readings to be taken in extremely fast flowing water and also allows for excellent maneuverability of the depth finder into locations under a bridge.
Side scan sonar is a specialized application of basic sonar theory. Although common for oceanographic and hydrographic survey work, side scan sonar has not been widely utilized for portable scour monitoring. Side scan sonar transmits a specially shaped acoustic beam to either side of the support craft, which allows for one of the most accurate systems for imaging large areas of channel bottom. A disadvantage to this method is that most side scan systems do not provide depth information.
Multi-beam systems provide similar fan-shaped coverage to side scan systems, but output depths instead of images. Multi-beam sonar is typically attached to the surface vessel rather than being towed.
Scanning sonar operates by rotating the transducer assembly, emitting a beam while the assembly (or "head") moves in an arc. Scanning sonar is performed by moving the transducer assembly, which allows it to be used from a fixed, stationary position.
Scour monitoring software allows transportation engineers to predict, identify, prepare for, and record potentially destructive flooding events through a secure internet connection. This type of system identifies the occurrence of a flood event and collects and processes relevant bridge information, several sources of real-time hydrological data and any bridge scour monitoring device data. Transportation officials are able to efficiently dispatch emergency personnel, bridge safety inspectors, and maintenance workers before, during, and after a flood event affects a state's bridge inventory.
Portable depth sounders with transducers have been used to monitor real time scour at substructure units during major flood events. The deck elevations and scour depths of concern are indicated on the Scour Action Plan. If the scour reaches the critical depth specified, the bridge is closed.
The Magnetic Sliding Collar (MSC) is a scour monitoring device. The magnetic sliding collar device consists of a stainless steel pipe driven into the channel bottom with a sliding collar that drops down the pipe as the scour progresses. The location of the collar is detected by the magnetic field created by magnets on the collar. Installations conducted in cooperation with state highway agencies demonstrated that this simple, low-cost instrument is adaptable to various field situations, and can be installed with the equipment and technical skills normally available at the district level of a state highway agency.
Figure 2.4.6 Scour Monitoring Collar
Figure 2.4.7 Scour Monitoring Collar Schematic
The basic components of a computer-based image system include: an imaging sensor, most commonly a solid-state camera; the image acquisition boards, which convert optical images into an array of digital information, representing the brightness values of the surface; and dedicated processor. The computer-based imaging system can provide two main types of information: spatial measurements and surface analysis. Spatial information encompasses two-dimensional or three-dimensional analysis, measurements and recognition. The surface analysis provides information regarding the color or gray-scale attributes of the target. For example, imaging systems are able to distinguish a flaw from the rest of the surface, and determine size, shape, location and even smallest color attributes of the deficiency. The field of view can be processed in a fraction of a second and can be on the order of 200 to 500 times the size of the smallest feature of interest.
This system works well in a clean environment, however if the item/member is very dirty or has debris surrounding it, cleaning may need to be performed prior to using a remote camera.
The high speed underclearance measurement system can mount on any vehicle with a trailer hitch receiver. The system measures the underclearance of a bridge at normal highway speeds. Along with the underclearance data, the GPS location is gathered. Software is used for the data acquisition, display and analysis. The bridge beam height is read to the nearest tenth of a foot. The GPS information can be pasted into a map program to obtain the structure location for future reference.
Figure 2.4.9 High Speed Underclearance Measurement System
Robotic devices for many applications are being developed by university researchers. High level and underwater bridge inspection are among these applicatons.
One example is the serpentine robot being developed that possesses multiple joints that give it a superior ability to flex, reach, and approach every point on the bridge. This robot is under development.
Other developments in robotic devices are presented in more detail in Topic 15.3.
Laser scanning technology can create accurate and complete 3D as-built models quickly and safely. These digital models are automatically combined with CAD design models to allow generation of “as-built” drawings for existing structures. This method can replace tedious field measurements for rehabilitation projects.
The majority of bridge inspectors use pencil and paper to record deficiencies on a bridge. They usually take a copy of the last inspection notes or report and "mark-up" changes since the last inspection. The inspectors input the current findings into the bridge owner's software and the inspection is updated.
Many State agencies are using Electronic Data Collection for bridge inspection.
Data recording hardware can include regular office computers, notebook computers or tablet PCs (see Figure 2.4.10) Some versions of these devices have been made to be more rugged and even “wearable” for use in the field.
Specialized software packages can provide a comprehensive set of solutions to manage, inspect, maintain and repair bridges. They allow the user to maintain a comprehensive asset inventory database, collect inspection data from electronic devices, keep history of inspection and maintenance records, assign inspection and maintenance requirements to each structural component, automatically generate inspection reports, and offer decision support.
AASHTO Pontis suports databases on bridge inspection and management. Many bridge owners use AASHTO Pontis based software and have developed programs to address their specific needs.
Figure 2.4.10 Tablet PC Used to Collect Inspection Data
Proper inspection equipment plays a key role in maintaining the safety of the traveling public and the inspectors. Inspectors who do not have the right equipment, may attempt to use an alternate piece of equipment that is not really designed for the job. Using whatever equipment is at hand, in an attempt to save time and money, can prove dangerous for the inspection team as well as the public. The best way to avoid these circumstances is to ensure the inspectors have the proper equipment for the job and that the equipment is serviced or replaced periodically. This responsibility lies not only with the inspector or team leader but also their employer. It is important that the employer make every effort to properly equip their inspection teams. Also, the inspector needs to be familiar with every piece of equipment and how to use and operate it properly and safely.
Safety fundamentals for bridge inspectors is presented in detail in Topic 2.2.
The two primary methods of gaining access to hard to reach areas of a bridge are access equipment and access vehicles. Common access equipment includes ladders, rigging, and scaffolds, while common access vehicles include manlifts, bucket trucks, and under bridge inspection vehicles. In most cases, using a manlift or bucket truck will be less time consuming than using a ladder or rigging to inspect a structure. The time saved, however, is normally offset by the higher costs associated with operating access vehicles.
The purpose of access equipment is to position the inspector close enough to the bridge component so that a "hands-on" inspection can be performed. The following are some of the most common forms of access equipment used in bridge inspection.
Ladders are used for inspecting the underside of a bridge or for inspecting substructure units. However, a ladder is used only for those portions of the bridge that can be reached safely, without undue leaning or reaching. The proper length of the ladder is determined by using it at a four vertical to one horizontal angle. When set up at the proper angle (1 horizontal to 4 vertical), the inspector is able to reach out horizontally, grasp the rung while keeping his or her feet at the base of the ladder (see Figure 2.5.1).
Figure 2.5.1 Inspectors using a Ladder with the Proper 1H to 4V Ratio
Ladders are also used to climb down to access members of the bridge. The hook-ladder, as it is commonly referred to, is fastened securely to the bridge framing (see Figure 2.5.2).
Figure 2.5.2 Inspector using a Hook-ladder
When using a hook-ladder, the inspector is tied off to a separate safety line, independent of the ladder.
Rigging of a structure consists of cables and platforms. Rigging is used to gain access to floor systems and main load-carrying members in areas where access by other means is not feasible or where special inspection procedures are required (e.g., NDE of pins). Rigging is often used when ladders or other access equipment cannot reach a given location (see Figures 2.5.3 and 2.5.4). Rigging is a good choice for a load-posted bridge that does not have the capacity to support an inspection vehicle.
Rigging does not interfere with traffic on the bridge and can be used in high traffic situations where lane closures are intolerable, and on toll facilities to avoid loss of revenue. Rigging may not be an option if there is not enough clearance to avoid interfering with passing features below the bridge.
Figure 2.5.3 Rigging for Substructure Inspection
Figure 2.5.4 Rigging for Superstructure Inspection
Scaffolds provide an efficient access alternative for structures that are less than 40 feet high and over level ground with little or no traffic nearby (see Figure 2.5.5). The Occupational Safety and Health Administration (OSHA) has specific requirements when working on scaffolding. Scaffolds may take longer to set up than it takes to inspect the bridge. For this reason, scaffolding is not normally used for bridge inspections.
A boat or barge may be needed to gain access to structures over water. A boat can be used for inspection, as well as providing access to areas for taking photographs. Also, a safety boat is required when performing an inspection over water (see Figure 2.5.6).
Figure 2.5.6 Inspection Operations from a Barge
A barge may also be used in combination with other access equipment or vehicles to perform an inspection. The barge may be temporarily anchored in place to provide a platform for a manlift or mobilization for underwater inspections.
Climbers are mobile inspection platforms or cages that "climb" steel cables or truss members (see Figure 2.5.7). They are well suited for the inspection of high piers and other long vertical faces of bridge members.
Floats
A float is a wood plank work platform hung by ropes (see Figure 2.5.8). Floats are generally used for access in situations where the inspector will be at a particular location for a relatively long period of time.
Figure 2.5.8 Inspector Using Float
Bosun (or boatswain) chairs are suspended with a rope and can carry one inspector at a time. They can be raised and lowered with block and tackle devices. Rappelling is a similar access method to the Bosun chair but utilizes different equipment and techniques (see Figure 2.5.9). However, both methods require the use of independent safety lines.
Figure 2.5.9 Inspector Rappelling Substructure Unit
On structures, where other methods of access are not practical, inspectors climb on the bridge members to gain access (see Figure 2.5.10). Safety awareness is of the utmost importance when utilizing this technique. When using this method, the inspector is tied off to the bridge using an independent safety harness and lanyard.
On some structures, inspection access is included in the design and construction of the bridge. These are typically found on long span structures or more complex designs. Although these inspection platforms only give access to a limited portion of the bridge, they do provide a safe and effective means for the inspector to work. The following are some examples of permanent inspection structures.
A catwalk is an inspection platform typically running parallel to the girders under the superstructure (see Figure 2.5.11). Catwalks can be used to inspect parts of the deck, superstructure and some portions of the substructure. The range of inspection area is limited to those locations near the catwalk.
A traveler is another permanent inspection platform similar to a catwalk except that it is movable. A traveler platform is typically perpendicular to the girders and the platform runs on a rail system between substructure elements (see Figure 2.5.12). Having the platform perpendicular to the girders allows the inspectors a wider range of movement and enables them to see more of the superstructure elements.
Figure 2.5.12 Traveler Platform
Handrails are also used to aid an inspector. Handrails can be used in a number of different locations on the bridge. On the main suspension cables, on top of the pier caps, and on the girder web are just a few locations where handrails may be built (see Figures 2.5.13 and 2.5.14). Handrails are typically provided to assist the inspector when free climbing on the bridge and give the inspector a place to secure their lanyard and safety harness.
Figure 2.5.13 Handrail on Girder Bridge
Figure 2.5.14 Handrail on Suspension Bridge
Currently, efforts are being made for robots to be used for inspection purposes. Though still early in the development stage, robots may prove to be an important addition to the inspector’s access equipment. Although a robot can never replace a qualified inspector, it can provide information that may not be visible to the human eye. A robot equipped with sonar capabilities can detect internal flaws in bridge members. Also, a robot can be used in situations that are too difficult to reach or extremely dangerous for a human.
There are many types of vehicles available to assist the inspector in gaining access for “hands-on” inspection of bridge members. The following are some of the most common types of access vehicles used in bridge inspection.
A manlift is a vehicle with a platform or bucket capable of holding one or more inspectors. The platform is attached to a hydraulic boom that is mounted on a carriage. An inspector "drives" the carriage using controls in the platform. This type of vehicle is usually not licensed for use on highways. However, some manlifts are nimble and can operate on a variety of terrains. Although four wheel drive models are available, manlifts are limited to use on fairly level terrain. Manlifts come in a number of different sizes with vertical reaches ranging from 40 feet to over 170 feet (see Figure 2.5.15).
Scissor lifts may be used for bridge inspections with low clearance between the bridge and underpassing roadway. Scissor lifts have a typical maximum vertical reach of 20 feet. These lifts are designed for use on relatively level ground (see Figure 2.5.16).
A bucket truck is similar to a manlift. However, a bucket truck can be driven on a highway, and the inspector controls bucket movement (see Figure 2.5.17). As with the manlift, a bucket truck needs to be used on fairly level terrain. Bucket trucks have a number of different features and variations:
A track-mounted man-lift provides access to areas with rough terrain that a conventional bucket truck would not be able to navigate (see Figures 2.5.18 and 2.5.19). By utilizing rubber tracks, track-mounted man-lifts can be operated in water, climb 35 degree slopes, traverse 25 degree side slopes, and navigate wet and muddy terrain.
Figure 2.5.18 Track-mounted Man-lift in a Stream
Figure 2.5.19 Track-mounted Man-lift on a Slope
An under bridge inspection vehicle is a specialized bucket truck with an articulated boom designed to reach under the superstructure while parked on the bridge deck. Usually the third boom has the capacity for extending and retracting, allowing for greater reach under a structure. Some of the larger under bridge inspection vehicles have four booms, allowing an even greater reach (see Figure 2.5.20).
Figure 2.5.20 Under Bridge Inspection Vehicle with Bucket
Variations and options available on different models include:
Figure 2.5.21 Under Bridge Inspection Vehicle with Platform
In most cases, even the most sluggish lift device will be quicker than using a ladder, rigging or free climbing to inspect a structure. The time saved, however, needs to offset the higher costs associated with obtaining and operating an access vehicle.
In assessing the time-saving effectiveness of an access vehicle, the following questions need to be answered:
The inspection time, safety and vehicle costs can then be compared to standard access equipment.
Safety is the primary concern on any job site, not only of the workers but of the public as well. The equipment and vehicles being used also have safety considerations.
Before the bridge inspection begins, an equipment inspection is performed. As a minimum, inspect access equipment as per the manufacture’s guidelines. Using faulty equipment can lead to serious accidents and even death. Check the equipment and verify that it is in good working condition with no defects or problems. If rigging or scaffolding is being used, check to ensure that it was installed properly and that the cables and planks are secured tightly. Use OSHA-approved safety harnesses with shock absorbing lanyards when using access equipment.
If the inspector is not familiar with the inspection vehicle being used, then take the time required to become accustomed to its operation. In some cases, formal operator training may be necessary or required. When operating any inspection vehicle, always be aware of any overhead power lines or other hazards that may exist. It is also important to be aware of any restrictions on the vehicle, such as weight limits for the bucket, support surface slope limits, and reach restrictions. Always be alert to your location. Do not extend the boom out into unsafe areas such as unprotected traffic lanes or near electrical lines. Use OSHA-approved safety harnesses with shock absorbing lanyards when using access vehicles.
