Asset owners have an abundance of ancillary structures under their supervision, some of which are lacking a well-defined inventory. One example of the ancillary structures are high mast poles that might undergo higher fatigue cycles. The mast pole is an isolated member with a single load path and no system redundancy. Ancillary structures such as these receive less inspection oversight than a bridge, primarily because of the critical nature of bridges. In other words, the failure of an ancillary structure has less impact than that of a bridge. However, due to the age of the Nation’s infrastructure, ancillary structures are requiring more and more attention from asset owners and the inspection community. NDE could certainly be a valued asset for evaluating ancillary structures, but the question remains as to how advantageous and how expensive evaluating them would be.

Scope of Work:

1. Scan and document States’ current practices in inspecting and assessing condition of ancillary structures.
2. Investigate and evaluate the value of deploying NDE to complement visual inspection.
3. Develop a risk-based approach to extend inspection intervals.
4. Draft a final report with the added value of NDE to supplement visual inspection, and a risk-based approach to use NDE to offset cost.

It is difficult, if not impossible, to engineer for extreme events such as flooding. These events can cause soil erosion or washout to the point where a structure’s foundation loses bearing capacity. Possessing the ability to determine the soil stability around a structure after an event like a flood could prove vital in determining road closures or repair needs.

Researching how NDE could be applied to better assess soil stability after flooding could prove fruitful.

Scope of Work:

1. Document potential damage to foundations caused by flooding.
2. Scan and document States’ current practices in assessing bridge foundation and soil stability after flooding.
3. Identify NDE methods that can be utilized after flooding to better assess the damage to the foundation and soil stability.
4. Draft a final report with recommendations to use NDE methods to assess bridge foundation after flooding.

Traffic ancillary structures include luminaires, sign structures, and traffic signal structures. They are inspected at the directive of the State and local transportation agencies. National Bridge Inspection Standards does not mandate their inspection¹. Unexpected failure of numerous light poles and signal structures across the Nation have been continuously reported for the last few decades. These failures are a significant safety concern. They have resulted in injury and death as well as damage to property. Programs to inspect pole structures have included periodic visual inspection coupled with NDE technologies. However, these programs have not been standardized with respect to how and when NDE technologies are deployed. FHWA’s Guidelines for the Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaires, and Traffic Signals includes limited information about the use of NDE technologies². Frequent and periodic inspection of ancillary structure inventories are generally not financially feasible. This lack of feasibility results from the size of the inventory and the geographic dispersion of assets. Frequent and periodic inspections also may not identify rapidly changing conditions arising from wind-induced vibrations.

Wind-induced vibrations are one of the main reasons for the fatigue and failure of ancillary structures. First mode vibrations are caused by strong wind gusts, and typically, result in higher amplitudes of vibration. This stress can lead to severe damage or outright failures depending on the amplitude of the vibration and type of ancillary structure. Second mode vibrations are caused by steady constant wind at lower velocities. These vibrations are often more damaging to the integrity of structures. They can also cause severe damage through fatigue. Other damaging factors, outside of fatigue, exist as well.

The objective of this research is twofold. To investigate the primary factors affecting the deterioration and failure of traffic ancillary structures and to study the feasibility of developing a warning system for capturing changing conditions affecting vulnerable structures that can be used for predicting and mitigating failures.

Scope of Work:

1. Conduct a literature review of research conducted on the monitoring and failure of traffic ancillary structures.
2. Collect and summarize the failures of traffic ancillary structures from across the Nation.
3. Identify the primary factors affecting the fatigue damage of ancillary structures using geographical, environmental, and structural features.
4. Develop a monitoring system in the controlled laboratory environment considering practical implementation.
5. Validate the warning system in field conditions.
6. Draft a final report with recommendations, procedures, and guidelines to implement the warning system in practical applications.

References

1. Federal Highway Administration. 2022. “National Bridge Inspection Standards 2022” (web page) https://www.fhwa.dot.gov/bridge/nbis2022.cfm, last accessed November 1, 2022.
2. Garlic, M. and E. Thorkildsen. 2005. Guidelines for the Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaires, and Traffic Signals. Report No. FHWA-NHI-05-036. Washington, DC: Federal Highway Administration.

Chloride ions accumulate on bridge-decks in geographic locations where salt is used routinely for winter conditions. As chloride concentrations penetrate to the level of embedded reinforcement, they accelerate the potential to cause corrosive reactions. These reactions lead to the early deterioration of bridge decks. The current practice to measure chloride concentrations requires destructive means to sample the concrete, usually by drilling or coring. Samples are then returned to a laboratory for analysis. Because these methods are destructive and expose the bridge deck to additional chlorides and deterioration if not properly repaired, a typical assessment will only include a select sampling that may or may not be reflective of the entire deck condition. Having the ability to measure chloride concentrations accurately and widely across the deck surface by a nondestructive approach would aid in improving the understanding of chloride accumulations. Early detection of conditions that can lead to corrosion of embedded reinforcement will allow for the implementation of cost effective, preemptive measures that extend the service life of bridge decks.

National Cooperative Highway Research Program (NCHRP) Innovations Deserving Exploratory Analysis (IDEA) Project 208 (published June 25, 2020) laid much of the groundwork to test the viability of using ground-penetrating radar (GPR) to measure chloride content in a truly nondestructive fashion (i.e., without requiring core samples).¹ The results proved promising, but further research is needed due to the limited number of bridge decks assessed in the IDEA Project.¹ The data highlighted that chloride levels could be determined by correlating the GPR signal attenuation to the moisture content in the concrete. Moisture content can be estimated by a measure of the dielectric constant from radar data. This suggests in theory that it may be possible for radar to estimate chloride content independently by measurement of signal attenuation and relative dielectric constant, without the need for calibration cores and laboratory chloride measurements. However, additional work is needed to determine the practicality of this theory. Including study of the optimal level of moisture required to produce meaningful results given that GPR can only detect and quantify chloride contents in the presence of moisture. If moisture is absent in dry concrete, GPR cannot detect chloride levels.

Additional research on the environmental (e.g., temperature, humidity) effects is required. Developing an understanding of the optimal test conditions to gain the most accurate prediction possible would be beneficial not only to a user but also for planning stages. Selecting a few bridge decks within different climate regions would be a prudent action.

Scope of Work:

1. Repeat the work of NCHRP IDEA Project 208 on bridge decks within different climate regions, which will increase statistical understanding of the theory under a wider assortment of variables¹.
2. Develop means and methods to measure chlorides without coring.
3. Assess degree of accuracy/reliability for measurements without coring.
4. Assess feasibility to measure chloride at traffic speed.
5. Develop models to predict degradation based on chloride content mapping.

References:

1. Alongi, A. J. 2020. NCHRP IDEA Project 208: Determining Bridge Deck Chloride Quantities Using Ground Penetrating Radar. Washington, DC: National Research Council.

The assessment of bridge decks by NDE is a growing application area that has significant potential to both reduce the operating costs and extend the lifecycle of bridge decks throughout the country with the application of the most cost-effective intervention at the most opportune time. Numerous NDE techniques have been proposed and have shown potential for identifying and characterizing common areas of deterioration related to corrosion, delamination, and degradation (in addition to locating reinforcement, cover dimensions, material properties, etc.). The primary issue facing State agencies is related to the cost-benefit (or return on investment) associated with the deployment of specific technologies. For example, if deterioration X is below limit Y, then the cost savings associated with finding it before it exceeds this limit would be Z due to the ability to deploy intervention/repair approach A versus a more expensive intervention/repair approach B. Importantly, this type of analysis is not meant to estimate actual cost savings but is geared more to identify techniques that have the potential to save money over the life of the bridge deck during the repair stage.

To provide guidance on which technologies to deploy, when they should be deployed, and how they should be deployed, a comprehensive study is required. This study must establish the ability of specific technologies to determine specific types and sizes of deterioration. Specifically, guidance is needed at each end of the deterioration timeline to identity those technologies that are most beneficial to making intervention decisions when deterioration is not yet visible to those technologies that are most beneficial to making intervention decisions when deterioration is more advanced. Once established, this information, together with the costs associated with various repair intervention techniques, can be combined to develop a suite of potentially economical deployment strategies.

In addition to studying NDE technologies, this study will also require defining specific thresholds at which NDE data will be evaluated to make informed decisions about intervention actions. The combined cost of NDE and the intervention costs will be compared with the expense of not collecting NDE data and waiting for visible deterioration to manifest itself. Such a comparison can define a potential “savings” associated with finding specific types of deterioration at an earlier stage.

Scope of Work:

1. Identify specific technologies to find specific types and sizes of deterioration.
2. Define specific thresholds at which NDE data will be evaluated to make informed decisions about intervention actions.
3. Develop guidance on the type of technologies that are most beneficial to making intervention decisions at each end of the deterioration timeline.
4. Develop a suite of potentially economical deployment strategies.

Bridge owners recognize the importance of preservation treatments for the extension of bridge deck service life and the impact these treatments have on the lifecycle cost of keeping bridges in a state of good repair. One approach is to use project-level decisionmaking, which can be facilitated by the integration of NDE methodologies into the bridge condition evaluation processes. More typically, bridge owners rely on visual and possibly sounding surveys to evaluate the condition of bridge decks. These data inputs are then evaluated using rudimentary decision matrices that group bridges into rough categories. The categories are generally based on the percent of delamination or general deck condition rating. Based on the grouping, the bridge may be recommended for preservation, repair/rehabilitation, or replacement. However, preservation actions are more advantageous when applied before delaminations fully develop or before deck deterioration becomes visible. Thus, there is a need for guidance on when consideration should be given to the incorporation of NDE tools in the bridge deck condition assessment process, particularly when such tools will provide reliable data that support the timely application of preservation treatments. Preservation treatments, when optimally applied over the assets’ lifespan, generally lead to a lower lifecycle cost for the asset.

In addition to determining the most appropriate time to incorporate NDE methods in the bridge deck assessment process, guidance is needed to select the best NDE method for a particular task and to develop decision matrices that indicate when certain conditions must trigger preservation actions. The development of an effective decision matrix should consider the accuracy and reliability of the various NDE methods deployed, as well as the environmental and external influences (e.g., chloride applications, freeze/thaw cycles, rebar coatings, traffic volume) that affect deck service life.

Scope of Work:

1. Define thresholds for NDE data for determining when preservation, repair/rehabilitation, or replacement actions should be recommended.
2. Perform a cost-benefit analysis.
3. Develop a decision-tree tool for the selection of NDE methods given needed accuracy and reliability, environmental and external influences as well as cost-benefit analysis.
4. Establish a programmatic approach for the application of NDE throughout the assets’ lifespan that can be easily incorporated into State-specific bridge condition evaluation manuals.

The midsection of web members of prestressed beams or other concrete members are prone to cracking. When this occurs and the performance of the member is called into question, extensive crack mapping and monitoring protocols may be invoked. These methods to obtain the measurements can take hundreds of labor hours and cause prolonged lane closures. From a measurement consistency perspective, the measurements can differ from one inspector’s perspective to another. Having the ability to perform crack, width, and length measurements quantitatively and qualitatively would ensure repeatability and accuracy for monitoring conditions over time and help with making more informed decisions.

Light detection and ranging (LiDAR) and trademarked technologies have the potential to measure and monitor cracking and microcracking of all bridge members of high concern. The technology, however, requires more vetting to ensure a wider application and more studies on its use under traffic speeds to minimize traffic delays. One form in which this can be achieved is using a Faro arm or handheld device type scanning approach during routine inspection or even packaging the technology to be drone deployable.

Attributes of cracking requiring documentation (e.g., width, length, orientation) in some concrete members can be quite minute. Therefore, understanding the limitations of the technologies to quantify a crack and its changes over time are vital for implementation and would further the understanding of how the technologies can be used for sustained mapping and reporting.

Scope of Work:

1. Perform a scan to see what technologies are on the market to measure concrete cracking.
2. Perform an assessment for each of the systems’ abilities.
3. Develop a technological system that could be easily packaged for bridge members of differing geometry that are subject to variable environmental conditions including lighting.
4. Reassess the performance of the systems on in-service bridges to verify their abilities to record quality data.

The corrosion of steel rebars in reinforced concrete deck adversely affects the durability and safety of bridge structures. Corrosion of rebars in concrete coupled with increased live loads from the roadway surface, causes punching thru-holes to be formed as corrosion adversely affects the punching shear resistance of concrete deck. This failure mechanism can be prevented if the corrosion initiation and propagation in the deck’s rebars are identified through conventional bridge inspections. Nonetheless, due to the presence of wearing surface on the top and the stay-in-place forms covering the bottom surface of the concrete deck, conventional methods might not be effective for this purpose.

As per the Manual for Bridge Element Inspection, Second Edition by the American Association of State Highway Transportation Officials bridge deck top or bottom surfaces that are not visible for visual inspection shall be assessed based on the available visible surface¹. If both the top and bottom surfaces are not visible, the condition shall be assessed based on indicators in the materials covering the surfaces. Despite the wealth of the knowledge available, no universal method has been proposed in the literature to evaluate the condition of the concrete deck based on a strength and failure mechanism approach. Therefore, research is suggested to evaluate the capability of available NDE methods to assess deck response to different failure mechanisms with a focus on punch-thru failures.

NDE methods are advantageous in their ability to be applied in a manner that minimizes or eliminates traffic disruptions. Further, NDE methods can be applied without destructive sampling thereby maintaining the structural integrity of the bridges to be examined.

Several State departments of transportation are facing the daunting task of maintaining an inventory of deteriorating structures using biennial inspections and regular maintenance activities. Sudden punch-thru failures can cause safety and mobility concerns especially in urban areas with large traffic volumes. Developing NDE methods for early detection of possible punch-thru failures in bridge decks will help bridge owners enhance budget allocations, improve decisionmaking, and maintain transportation infrastructure in a state of good repair.

The objective of this proposed research is to investigate the feasibility of NDE methods in detecting conditions in deteriorated bridge decks (and beams) that can lead to compromises in strength or possible failures with a focus on punch-thru failures.

Scope of Work:

1. Collect and summarize NDE methods with applicability (both pros and cons) for evaluating bridge decks (beams) and the types of failure that can occur, including punch-thru failures.
2. Use the NDE methods identified from Task 1 to investigate decks (beams) in various stages of deterioration/distress to evaluate the condition of reinforcing and concrete at various ages relative to the different failure mechanisms identified in Task 1.
3. Perform NDE on sample bridges to determine in-situ conditions of the concrete deck (beams) and the reinforcement. Field tests and sampling should include potential measurements in the areas of chloride sampling at various depths, and core extracting for a visual examination of reinforcing conditions.
4. Create a final report (along with recommendations, procedure, guidelines, etc.) to implement the developed research in practical applications.

References

1. American Association of State Highway Transportation Officials (AAHSTO). 2019. Manual for Bridge Element Inspection, Second Edition. Washington, DC: AAHSTO.

Problem/Background:

The certification of personnel performing NDT of steel and concrete bridges in field inspections is fragmented between certification bodies and varies immensely from one owner to the next. However, the knowledge, training, and experience of inspectors performing NDT is paramount to obtaining consistent and accurate data on the condition of the structure so that key asset management decisions can be made.

Studies have shown that even inspectors who are certified and practicing in other sectors, such as nuclear or oil and gas, underperform when placed on a bridge field inspection project. Although some literature exists on the effects of this resulting gap in knowledge and experience, there is no research that examines existing practices of owners aimed at combatting this deficiency or synthesizing the available certification programs. This project will provide a synthesis of personnel certification and qualification practices in bridge inspection and their effectiveness based on a national and international literature search and on a survey of highway bridge owners around the world. This information can be used to assess the effectiveness of the practice from both performance and practicality perspectives and to develop guidelines for a consistent certification program for bridge owners. This approach will fill one of the large gaps in the determination of reliability of NDT methods for bridge structures.

This synthesis will provide transportation agencies with the necessary background and guidance for the practice of personnel certification and qualification in bridge field NDT inspection. Specific questions to be addressed are some of the following:

• What research literature is currently available concerning the practice of personnel certification and qualification in bridge field NDT inspection?
• How often and under what circumstances has the practice of personnel certification and qualification in bridge field NDT inspection been employed in transportation projects?
• What are the practices in personnel certification (and recertification, if any) and qualifications employed by various owners?
• Were these programs internal or external?
• What are the requirements of the owners for outside contractors who perform NDT?
• Has the practice been considered acceptable by certification bodies both here and internationally?
• Was consideration given to the circumstances in which the personnel were to operate, that is, field inspection versus fabrication inspection?
• What were the results of this type of personnel certification and qualification?
• What kinds of metrics were employed to determine the effectiveness of these programs?
• Is the practice cost-effective relative to the technician performance, information obtained, and potential resulting asset management decisions?
• What actions or considerations are necessary to document over the lifetime of the program or employment of the inspector?
• What continuing education is employed by the departments for these inspectors?
• What are the costs associated with certification programs?
• Is there a need for regulating agencies to develop an NDT certification program geared specifically toward highway bridge inspections?
• Is there an interest in State and Federal bridge-related agencies to participate in an effort to develop personnel certification?
• Which organization should be responsible for developing a centralized personnel certification program for bridge inspections?

The results of this study will provide transportation agencies with the necessary information to evaluate the applicability of these personnel certification and qualification programs for their NDT technicians, to justify their applicability as appropriate to regulatory agencies, and to develop specifications for its implementation during bridge inspection.

Scope of Work:

1. Perform a literature review on the current practice for personnel certification and qualification programs in NDE, with a focus on:
   1. general and special requirements for a list of intents of analysis.
   2. available standards and specifications.
   3. costs and benefits from the owners’ perspectives.
2. Identify technical and nontechnical challenges for implementing personnel certification and qualification programs.
3. Develop guidelines for personnel certification and qualification in NDE.

Bridge and tunnels of substantial size, complexity, and/or importance are few across the Nation but demand more attention from their owners for maintenance and preservation than the rest of the inventory. The fiscal magnitude of the management program for these structures, the importance of these structures for the economy, and the safety implications associated with movable bridges and tunnels demand the development of an objective, data-driven rationale for selecting projects. For example, Virginia’s 25 complex structures, out of more than 21,000 structures in the inventory, require nearly 43 percent of the entire maintenance funding in the recent budget estimation. These assets are massive, important, and disparate in need. Prioritizing the maintenance need among these complex structures involves complicated engineering decisions. A rational process is needed for prioritizing projects that range from installing a fan for a mountain tunnel to designing a drive system for an urban movable bridge on an interstate route.

There is a crucial research need for developing a risk and condition-based structural-health monitoring system for movable bridges and tunnels as well as tools that will enable the health index to be employed for lifecycle project prioritization and performance management.

Scope of Work:

1. Identify complex structures across the Nation and the relevant factors that went into the selection process.
2. Review and evaluate the dominant deterioration mechanisms for these structures.
3. Develop a decisionmaking matrix prioritizing the future vulnerability of these components.
4. Review structural-health monitoring methods for these applications.
5. Develop a long-term monitoring plan for these structures.
6. Write the report with the final findings.

Concrete beams are often subject to impact damage from motor vehicles. However, unlike steel girders, the structural soundness attributable to residual damage is much more difficult to evaluate by nondestructive means. Research projects based on composing a synthesis, gathering testimonials, and compiling industry-proven applications are needed to help asset owners improve their assessments of damaged concrete members.

The assessment/evaluation of impact damage is vital to the decisionmaking process to determine repair, replacement, or closure of a bridge. Having more tools in the toolbox to help with assessment/evaluation would be beneficial, particularly when damage may be hidden from view. Currently, NDE of damaged concrete bridge members is rare because of the lack of confidence in the data and the ability to easily apply technologies with quick turnarounds in analysis. Although the extent of concrete loss, cracking, fractured reinforcement/strands, and other damage is apparent in severe impacts, the damage that exists at the periphery of large impacts or throughout lighter impacts may not be readily quantified. Research into the NDE methods that may be applicable in these cases would help the structural engineer by providing a means for data-driven decision making.

NDE’s ability to assess damage, particularly for unseen conditions, is an attractive feature for helping to implement data-driven decision making as endorsed by the Moving Ahead for Progress in the 21st Century Act and the Fixing America's Surface Transportation Act ^1,2. Research on the best test methods to employ in assessing impact damage and their accuracy and reliability is needed. NDE data that can be quickly obtained and assessed can be used by the structural engineer to improve decisionmaking.

Scope of Work:

1. Gather a list of common types/locations of impact damage to concrete members.
2. Identify NDE methods and techniques that are applicable to different types of damage.
3. Rate the methods for use and provide accuracy and error data.
4. Provide detailed examples of how the data could be included in the decisionmaking process.
    

References

1. Office of the Federal Register. 2012. H. R. 4348. Moving Ahead for Progress in the 21st Century Act https://www.govinfo.gov/content/pkg/BILLS-112hr4348enr/pdf/BILLS-112hr4348enr.pdf, last accessed November 1, 2022.
2. Office of the Federal Register. 2015. Pub. L. No. 114–94, Fixing America's Surface Transportation Act. https://www.govinfo.gov/content/pkg/PLAW-114publ94/pdf/PLAW-114publ94.pdf, last accessed November 1, 2022.

Water infiltration is a common defect encountered in tunnel structures. However, the degree of severity/acceptance criteria associated with tunnel leakage varies and is a matter of debate. Although every structure has a design life, poor control/management of leaks can reduce this expectation. Given the age of tunnels across the country, rehabilitation projects are in high demand. One of the most important details in any tunnel rehabilitation project is addressing the challenge of leakage. Additionally, tunnel maintainers spend a lot of time knocking down ice so that the ice does not hit vehicles travelling through the tunnels.

Monumental amounts of effort can be spent combatting leaks, and the result typically does not yield a completely watertight tunnel. Methods of addressing tunnel leakage are hardly one size fits all. It is important to match the appropriate mitigation measure to the relevant leak type/source.

The objective of this research is to document tunnel owners’ methods and lessons learned in controlling leaks.

Scope of Work:

1. Review existing tunnel leak types.
2. Develop a list of leak classifications.
3. Review available products for crack injections.
4. Review other methods such as hydrodemolition and shotcrete of tunnel walls.
5. Develop standard details for noncrack injection solutions (drainage troughs, etc.).
6. Develop a flow chart/decision matrix of mitigating leaks.

The objective of this study is to assess the reliability of NDE technologies for the condition assessment of tunnels. For decades, technicians have performed NDEs of concrete and tunnels with traditional techniques such as hammer sounding and visual inspections. These techniques have proven to be successful in detection of mitigation/repair needs of various issues associated with cementitious-based infrastructure. Due to the success over the years and quick turnarounds for reporting, engineers have developed a high level of confidence in using traditional NDE methods as opposed to the more advanced techniques available today.

Advanced NDE techniques such as GPR, infrared thermography, impact echo, LiDAR and others have been explored through innovation and grant projects for many years. The results of those projects have routinely returned the same conclusions of inconclusive/noncomparative data to traditional methods and high cost for implementation. These results have promoted a need to develop research on the reliability of the more advanced NDE methods for owners/engineers to gain confidence using them and understand their reporting of results.

Advance NDE methods generally provide outputs in color palettes or waveforms that are translated to color palettes and diagrammed on a map. When compared with traditional methods, the mappings have shown the advanced methods to be overly conservative or inaccurate. This inaccuracy could be caused by several different factors that affect the inspection results, including variations between the capabilities of the NDE technology as compared with more traditional assessment techniques. For example, hammer sounding is effective for detecting delaminations/voids, whereas the response of GPR technologies is more aligned with the detection of moisture and gross delamination or voids. As a result, comparisons between the two methods often vary significantly. Technology users would develop a high confidence level, if a study to determine the reliability of detection flaws, while minimizing false calls, was performed.

In addition to studying the reliability, accurate reporting to provide an efficient and quick deliverable is highly desired by the owners and end users of the data. For example, LiDAR is one technology used to detect and measure cracks; if LiDAR data could then be overlaid on a Computer Aided Design and Drafting (CADD) file or other model for ease of locating in the field, and condition monitoring over time, that would make huge strides toward implementation and use. Developing these files, either CADD or other, will undeniably involve more labor hours. Therefore, studying the extra efforts to turn these deliverables around quickly, for example, less than 30 d, would also need to be evaluated.

Scope of Work:

1. Perform a reliability study of existing structures being replaced and compare them to traditional methods.
2. Perform a verification of results from the reliability study by destructive means and methods.
3. Research and develop best practices for collecting and displaying data in an easy to understand/ maintain deliverable for the owner and end users.

The safety and reliability of tunnels relies on both structural and mechanical systems being maintained in a state of good repair. Structural Health Monitoring (SHM) has been fairly widely explored for use on bridges but has not been deployed on tunnels. Condition Monitoring (CM) of mechanical systems has been even more well established in sectors such as oil/gas and aerospace but has not been widely adopted for mechanical systems used in tunnels. Inspection and monitoring of tunnels is lagging due to the potential higher impact on the traffic disruptions and proven assessment methods. There are several reasons for this dilemma:

1. There are significantly fewer tunnels than bridges in the United States, particularly on the highway system, and uniform guidance has been less well established.
2. Tunnel access generally requires partial or full closures due to the lack of shoulders and/or staging areas. Closure is also problematic for highways due to congestion and length of detours. Closure is also problematic for railways because maintenance outages disrupt train schedules. Constrained service windows lead to inadequate inspection and deteriorating conditions.
3. The exchange of information between owners (rail and highway) has been limited.
4. The exchange of information between mechanical and heating, ventilation, and air conditioning manufacturing companies and tunnel owners is point-of-sale only.

Tunnel construction can be affected by geotechnical issues in the construction and adjacent zones. In-service tunnels can be subject to structural damages during their service life, such as cracking, reinforcement corrosion, and water ingress. The potential for the collapse of wall elements also exists. Monitoring presents an opportunity to mitigate such risks during construction and throughout the life of the tunnel.

This synthesis will provide transportation agencies with the necessary background and guidance for designing and procuring SHM and CM systems and services to provide real-time or near-real-time condition information to reduce the frequency of closures for inspections and repairs. Specific questions to be addressed include:

• What research literature is currently available concerning SHM and CM of tunnels and tunnel systems?
• What structural or mechanical systems warrant monitoring in a typical highway, transit, or rail tunnel?
• What are the conditions and/or deterioration states for which SHM and CM systems can be used in tunnels?
• What SHM is available for tunnel construction risk mitigation?
• What SHM and CM are in use in highway tunnels in the United States (in addition to standard inspections following the Tunnel Operations, Maintenance, Inspection, and Evaluation (TOMIE) Manual)⁽¹⁾?
• What SHM and CM are in use in highway tunnels abroad?
• What SHM and CM is in use in transit or rail tunnels in the United States and abroad?
• What vendor qualifications are in place by tunnel owners for this type of system or service procurement?
• What kinds of metrics were employed to determine the effectiveness of these programs?
• Is the practice cost-effective relative to periodic inspection and associated maintenance of traffic or maintenance of way?
• What actions or considerations need to be documented over the lifetime of the system?
• What training is necessary for an owner to take control of the system and its data management and analysis?
• What are the costs associated with operating and maintaining SHM and CM systems?
• What are some of the challenges associated with power, data storage, communications, and information technology security in a tunnel environment?
• What are some of the challenges with data management and analysis?
• What systems are available for monitoring fire suppressant, ventilation, and other mechanical systems within tunnels?
• What do standards such as National Fire Protection Association 502 say about monitoring ⁽²⁾?

The results of this study will inform transportation agencies so that they can evaluate, design, and develop specifications for SHM and CM systems, services and their implementation in tunnels.

Scope of Work:

1. Perform a literature review on:
   1. the intent of analysis when performing SHM and CM on tunnels.
   2. HM and CM technologies for tunnels, corresponding to each intent of analysis.
   3. return on investment of SHM and CM technologies, corresponding to each intent of analysis.
2. Identify technical and nontechnical challenges when performing SHM and CM on tunnels.
3. Identify best practices in data management and processing for SHM and CM technologies.
4. Surveying personnel training, qualification, and certification requirements.   

References

1. Bergeson, W. and S. Ernst. 2015. Tunnel Operations, Maintenance, Inspection, and Evaluation (TOMIE) Manual. Report No. FHWA-HIF-15-005. Washington, DC: Federal Highway Administration.
2. National Fire Protection Association (NFPA). 2023. NFPA 502 Standard for Road Tunnels, Bridges, and Other Limited Access Highways. Quincy, MA: NFPA.

Wall finishes vary by tunnel with every tunnel having their own unique requirements. When specifying wall finishes, consideration should be given to performance during washing, fires, lighting reflectivity, and protection from the elements. Among the many rehabilitation projects and new tunnel projects emerging today, wall finishes are becoming an important detail that requires more attention. It is estimated that this research will take 12 months to complete and will require $100,000.

New tunnel designs and existing tunnel rehabilitation projects contain many high priority and complex issues, the details involved with finishes can often be over simplified and result in premature degradation or ongoing maintenance issues.

The objective of this research is to document considerations and lessons learned for tunnel wall finishes and gathering past project details/standards.

Scope of Work:

1. Review existing tunnel wall finishes (material, condition, performance).
2. Develop a list of finishes performing best (service life, etc.).
3. Review existing project specifications, design requirements and details.
4. Review available products for wall finishes.
5. Develop recommendations for the best specifications and details.