Undertaking development of nondestructive evaluation (NDE) capabilities that then need to be promoted for consideration of the hammer is search of a nail. Fundamentally issues with life-cycle cost benefits are raised but cannot be provided a prior. This research needs statement (RNS) essentially proposes that asset management plans be developed before the structure is fabricated and erected so that structural integrity will not just be achieved at commissioning but maintained during the life of the structure.

Ideally an asset management plan is part of the planning and design process for a structure. All bridge structure designs can be affected using a variety of materials and details. Such variations will often impact the preventive and condition-based maintenance and eventually the preservation actions necessary to sustain the structural integrity and safety of the bridge components during the life-cycle.

If a structure is similar to other structures and experiences similar service, then the asset management plan might be similar and can be accomplished by data gleaned from the safety inspection required by the National Bridge Inspection Standards (NBIS). However, even for a network of similar structures if an asset management plan involves condition-based action, data gleaned from sensors assessing the internal condition without surface indications might be required. This RNS in principle might address these sorts of applications but it is intended for situations more typical of monumental, or signature bridge as well as unique bridge designs, e.g. moveable bridge designs and accelerated bridge construction projects.

Currently risk-based approaches are being considered for routine bridge safety inspections. A reasonable expectation is that the frequency of inspection for a new bridge ought to be lower than for older bridges. Unique bridge designs or those constructed with new construction approaches, however, might raise concerns regarding whether the new structure will perform as expected and if the safety of workers might be endangered with a previously unused construction approach.

Research is needed to establish a paradigm that establishes the asset management plan for a bridge structure during the planning and design phase. The planning paradigm should consider the nature of the deterioration of all of the bridge components along with the expected rate of that deterioration, based on the expected service. Actions deemed wise (cost-effective) will dictate the appropriate structural health monitoring (SHM) process(es). If necessary, provisions of the design will incorporate the necessary support framework for the monitoring system power and communication. For specialized construction the planning and design process should also consider situations that pose unique loading(s) of the structure during erection that might pose a danger for construction workers or the public. This will dictate additional, or pre-service SHM processes to monitor for unexpected structural response, e.g. during ABC projects.

Scope of work:

1. Research deterioration and expected deterioration based on service life.
2.  Research cost effective measures for implementing SHM at as part of the design and construction.
3. Use the findings of task 1 and 2 to develop the framework for an asset management plan during the planning and design stage.

Transporting long bridge elements over long distances of highways might from time to time induce large amplitude load cycles. Predicting these occurrences by surveying the route is impractical, if possible. While precautions might be taken to support these elements the uncertain route contour suggests that monitoring of the elements during transit for possible deterioration due to such mechanical loading is needed. Solutions that support quantitative assessment of the nature and location of any transport induced deterioration are needed. Solutions that work equally well for steel and concrete elements are most desired, however, solutions for either will be considered. Deterioration of particular concern for steel are low frequency large amplitude strain cycles that do not result in obvious distortion but might reduce fatigue service life. Similarly, for concrete elements deterioration which occurs but is not readily detected visually are of particular concern.

Scope of work:

1. Research how instrumenting long bridge elements during transportation can help determine areas that might have undergone unexpected loading.
2. Develop an outline for where instrumentation should be placed and thresholds to trigger if follow-up NDE should be performed at the project site.

The evaluation of construction materials under a planned and systematic testing program should provide confidence that completed transportation projects will perform satisfactorily in service. Thus, obtaining initial data on the material properties and the workmanship of completed transportation assets is key to predicting their future performance. Fortunately, the required quality of construction materials for transportation projects are well defined within the industry and by guidance documents authored by the FHWA and transportation asset owners. Methods for ensuring the required quality are typically described by quality control (QC) and QA plans, which also describe the procedures used to sample, test, and accept materials.

The quality and types of data obtained during the construction process are important for confirming that the finished product or facility was constructed using quality materials as defined by the specifications and owner’s requirements. However, additional guidance is needed to ascertain the types of data and tests required to characterize the completed structure more fully for purposes of extrapolating its future performance and mitigating quality- and workmanship-related risks.

Advancements in nondestructive technologies both for field and laboratory materials testing, as well as improvements in the overall programmatic management of QA and QC programs in relation to these technologies, can be leveraged to provide a better foundation for the assessment of future performance of recently completed transportation assets. Additionally, new technologies allow for increases in both efficiency and safety during the materials sampling and testing process.

Research is needed to determine the ideal benchmarks and associated technologies that are required to characterize completed transportation projects so that future performance can be accurately predicted. Such research should also describe the benefits derived from the use of new technologies for improved efficiency and safety. Lastly, the proposed research should describe how new technologies are used and their role in providing QC of more traditional testing methods.  

Scope of work:

1. Research and determine the ideal benchmarks for NDE data using a variety of NDE techniques to be used for predicting performance over time with subsequent data measurements.
2. Outline the benefits for using new technologies for improved efficiency and safety.
3. Develop a report describing how new technologies relate to the current traditional testing methods.

Post-tensioned tendons have become an essential part of construction practice for concrete bridge structures. Generally, the post-tensioned tendons are enclosed in a duct that might be embedded in the concrete element or remain external to most of the concrete member being loaded in compression balancing the tension imposed by the tendons.  The tension is retained by anchorages. To prevent corrosion of the high-strength steel tendon wires the ducts are filled with grout. Typically, in USA the grout is cementitious and is pumped into the duct following the insertion and tensioning of the tendons.  Care must be taken to assure that the grout composition is maintained without separation and that air voids do not occur within the duct especially at low points where water might pool and subsequently lead to corrosion of the tendon wires.  

Maintaining the integrity of the post-tensioned tendons is essential for the safety of the structure. Slippage of the tendons in the anchorage or breakage of corroded strand wires will result in loss of tension and in turn reduce the compression of the concrete members which can result in structural loading becoming tensile and leading to cracking of the concrete member.

A means of monitoring the tension in the tendons directly is needed.  Ideally the solution will enable remote monitoring of the measured tension or provide an alert if the tension drops by a specified amount.

Scope of work:

1. Research technologies capable of monitoring tension in strand members.
2. Develop means and methods for accurately and remotely monitoring tension in tendons of post-tensioned structures.

Electrically isolated tendon systems (EIT) have a history of use throughout Europe for monitoring the installation and long-term performance of post-tensioned tendons. More recently within the United Stated, pilot projects have been introduced in the northeast and southwestern portions of the country. These pilot projects are being developed to gain a better understanding of the climatic effects on the EIT system. Beyond these pilot projects there is still room for exploration of other potential uses, limitations, and training opportunities.

The EIT system works by measuring the electrical resistance between the stressed tendon and the mild reinforcing steel. A common practice in the USA is the use of epoxy coated mild reinforcing steel for added corrosion protection. This practice of using epoxy reinforcing steel does not lend itself well to being used with the EIT system because the epoxy coating on the mild steel behaves as an insulator. Some work has been done to use EIT’s with epoxy coated reinforcing steel acting as a conductor but recommendations to date are the use of longitudinal and transverse main conductors. Additional research could be conducted in this area to analyze possible changes to this system or consideration for other reinforcing steel such as galvanized and stainless steel.

Beyond the typical usage of the EIT system, there exists a possibility to determine grout voids using capacitance measurements. Prior experimentation on concrete has shown measurable capacitance changes related to moisture which prompts the question, could voids be detected using the EIT system.  

The greatest obstacle for using the EIT system in the United States is the lack of knowledge and understanding of electrical characteristics by civil engineers. According to studies in Europe, the development of post-tensioned installer training centers is vital to the adoption of EIT systems. This research should seek to develop Creating a programmatic outline for installer training courses and facility capabilities that will serve as the basis for wider adoption of EIT systems. To this end, the following scope of work is proposed. of what a training center should cover here in the USA would be key to the implementation across all 50 states.

Scope of work:

1. Review the current successful practices regarding EIT.
2. Determine methodology/best practice for using EIT’s with epoxy coated rebar.
3. Assess the feasibility of detecting voids after grouting.
4. Outline the scope and deliverables for a PT installer training center.

The occurrence of deficiencies is inevitable in reinforced-concrete construction projects. Deficiencies may include but are not limited to honeycombing, debonding, cold joints, cracking, inadequate cover, strength development issues and more. These issues can delay construction until they have been resolved. Associated delays can be costly for every entity involved, and the extended disruption to mobility makes for an unhappy general public. The efficient and timely mitigation of these problems has always been a challenging task for any project team.

The traditional approach for assessment of such construction-related issues has been limited to visual surveys, often in conjunction with limited nondestructive evaluation (NDE) and/or destructive probing, which provides limited insight into the severity and extent of the area requiring further mitigation. Thus, there is a need for reliable, accurate, and rapid condition evaluation using more sophisticated technologies that would enable the owners and contractors alike to more efficiently resolve the problems while minimizing the cost and disruption to the construction schedule.

NDE services are being increasingly used in construction for various purposes; they can help address non-compliance reports (NCRs) stemming from poor workmanship (for example honeycombing caused by improper consolidation or delays in concrete placement), inadequate quality of the product (for instance cold joints caused by unworkable fresh concrete), or environmental impacts (for instance low strength caused by placing concrete in a rainy day without proper mitigation for excess water). Additionally, NDE can assist in determining the extent of the area that needs to be repaired, followed by assessing the post-repair conditions.

However, often times, different parties in the construction team have competing financial interests that could potentially jeopardize the suitability of the test methods selected to evaluate the deficiency and how the data are interpreted. Establishing which technologies need to be deployed for a specific construction-related concern and providing guidelines as to how the results need to be interpreted in the project specifications can significantly reduce such risks. This ensures that everyone on the project team including the owner, the contractor, the material supplier, and the design team all have the same understanding of the required assessment approach once a problem arises. This further eliminates the risk of improper use or application of NDE, which could be costly and time-consuming. Additionally, establishing specific criteria for the testing quality eliminates the risk of using subpar NDE services and sets expectations of all parties before construction begins.  

Research on the use of NDE requirements in construction specifications is needed. This research should include application-based case studies to quantify the cost-benefit ratio of using NDE to help resolve specific construction-related issues and to support acceptance criteria. The research results can be used as guidelines for expanding the use of NDE in troubleshooting and resolving construction problems while reducing the costs associated with the mitigation measures.  

Scope of work:

1. Research and develop NDE requirements for construction.
2. Develop an NDE cost to benefit ratio matrix for routine construction problems with construction unit of measures.
3. Develop some quality acceptance standards for various NDE modalities used during construction.
4. Write a report for how NDE could be used for troubleshooting and problem solving construction problems.

Guidance related to nondestructive evaluations (NDE) exists for structure elements such as decks and girders. However, very little guidance or information is provided to owners for NDE of the substructures or foundations. Encountering issues with foundations during construction that was not originally anticipated occurs more often than stakeholders would like. This prompts a need to perform investigations, monitoring and/or remediations.

Potential areas of interest for NDE of Substructures during construction are driven steel piles, drilled shafts, mass footing concrete, embankment settlement and slope stability. Each of these structural or quasi structural elements has some known NDE testing technology associated but none that are fully developed for owners/decision makers to programmatically implement by way of contracts. Or, have a great understanding of the technology in the case of an isolated incident to request use of NDE. Due to the lack of knowledge and understanding the use of NDE for substructures is generally limited or forgotten when in fact there is great potential for added benefits.

Areas of interests and technologies for study:

• Driven Steel Piles – Pile Dynamic Analysis uses strain gauges to monitor the stresses and integrity of the pile as it is being driven
• Drilled Shafts – Thermal Integrity Profiling works by embedding thermal sensors along the reinforcing cage. As the concrete begins to cure noticeable temperatures changes are monitored thus relating this back to the overall profile of the shaft or potential defects that may exist
• Mass footing concrete – Thermal Sensors to monitoring proper curing of concrete
• Embankments Settlement – Survey Monuments, Light Detection and Ranging (LIDAR), Unmanned aerial systems (UAS)
• Slope Stability – Inclinometers, LIDAR, UAS

Developing information for these studied areas could be published on the NDE Web Manual as public information. The researching and information sharing for these technologies also comes with the added benefit of workforce development. By having a more knowledgeable workforce the appropriate tools, in this case NDE technology, can be selected for a given construction scenario.

Scope of work:

1. Research NDE technologies for substructures.
2. Develop a high level overview of the science behind each technology.
3. Develop a list linking NDE technologies that can be used for various substructure problems.
4. Develop and publish findings as an easy to use web tool.

Nondestructive Evaluation (NDE) techniques have been advanced as a critical tool for determining the conditions present in existing bridge decks so that appropriate preservation, repair, or replacement decisions can be made. In most instances, a suite of NDE tools are used to explore the existing conditions of the deck. For example, Ground Penetrating Radar (GPR) can be used to measure concrete cover, Infrared Thermography (IR) can be used to measure the location and limits of delaminations, and electrical resistivity can be used to characterize the corrosive environment within the deck. These tools provide data that when evaluated together can predict how the deck will perform over time, and thus have an impact on the interventions that may be selected. When the findings of these evaluations determine that localized, patching repairs are the most appropriate intervention, a set of drawings are prepared, and the project is bid. The identified defects are formed into rectilinear shapes based on the IR surveys and shown on scaled plan views. However, when the work actually takes place, the contractor does not apply the same level of sophistication to determining the location of each repair. Because the drawings are prepared at a size that makes scaling of repair locations inaccurate, the contractor or field engineer will perform sounding surveys to locate areas for patching. This process gives rise for concern that those performing field surveys prior to repair are not as well trained as the engineering and NDE specialists who studied the bridge during the initial investigation. Moreover, this process does not include locations where a suite of NDE methods may have identified a location where patching should be conducted because of elevated corrosion activity but which has not yet demonstrated detectable delaminations. These factors coupled with the lack of resolution of sounding methods as compared to more sophisticated NDE methods may result in locations of the deck going unrepaired. If this occurs, the service life of the repairs and deck is shortened.  

Research into the benefits of using NDE testing to guide construction is required to understand if the effects of current construction practices are effective in capturing the limits of deterioration identified during the investigation. This research should include review of current practices where NDE techniques are used to derive information for development of construction plans and specifications as well as a review of how the work is actually carried out. Deck repairs completed using current procedures should then be restudied using the same suite of NDE tools that were deployed during the investigation to understand if current construction practices are effective in locating and repairing defects that were expected to be included in the work. The advantages and disadvantages of NDE testing as part of the construction process should also be studied.

Scope of work:

1. Research current practices for how NDE data is used to develop construction plans and specifications.
2. Research how the plans developed with NDE data are carried out during construction.
3. Reevaluate the repair areas with NDE to access whether the construction practices used to outline the locations are effective.
4. Research advantages and disadvantages of NDE testing as part of the construction process.

There are a number of corrosion-based service life models currently available in the marketplace that predict the performance of steel-reinforced concrete exposed to chlorides. These models rely on a myriad of generalized simulations and assumptions, and in the case of mechanistic models can be refined through the use of nondestructive technologies. For example, Ground Penetrating Radar (GPR) has proven effective in determining the location depth of embedded reinforcement and spatial distribution of delaminations. Absent GRP data, the models use project-specified cover depth and may or may not consider standard deviations based on construction tolerances. With GPR scans, the cover depth can be aggregated for similar elements and analyzed to develop descriptive statistics, typically using lognormal distributions. Such analysis of reinforcement depth improves the model’s predictive capabilities. As such, owners seeking to use service life models in the future should consider obtaining rebar cover measurements using GPR as part of the overall construction quality control plan for the completed structure. In this instance, GRP scans can be performed prior to opening the bridge to traffic.  

Mix design and material properties of the concrete have a significant influence on the time required for chlorides to reach the embedded reinforcement. Typical construction quality control procedures require mix designs to be checked through the use of material submittals and batching documentation, while material properties such as strength, slump, placement temperature, etc. are measured in the field through the use of control cylinders. The addition of permeability testing as part of the quality control process would aid in developing more accurate service life models. Concrete diffusion coefficients can be determined using the Rapid Chloride Permeability Test or the NT Build Test. Owners seeking to use service life models in the future should consider expanded materials testing as part of the quality control process.

Cracking issues are not commonly addressed by current service life models, yet it is generally accepted that cracking will facilitate ingress of chlorides and moisture toward the interior of the concrete deck and the embedded reinforcement. Image-based methods have gained wider acceptance recently and show promise in identifying the density and width of cracking, while impact-echo and ultrasonic pulse velocity methods have proven effective in determining crack depths. So while NDE methods can be used to identify cracking geometries, research regarding the correlation of crack widths and densities to expected service life are lacking.

This research would seek to describe improved data collection strategies as part of the quality control process that would support the use of service life models for future determination of preservation, maintenance, and rehabilitation actions. The research would describe the benefits of expanded quality assurance testing during construction to obtain NDE data or additional materials testing as compared to the use of generalized assumptions or data collected later in the life of the structure. Finally, the research would study ways to incorporate NDE methods for crack detection in the context of service life models in an effort to expand how these technologies can be used.  

Scope of work:

1. Research data collection strategies for improved quality control to support service life models.
2. Research the benefits of obtaining NDE data and materials testing during construction.
3. Research how NDE methods can be implemented for crack detection and included in service life models.