Rebecca A. Atadero

Bridge Information Modeling for Inspection and Evaluation

AbstractThis paper presents a method and prototype implementation for tracking and assessing the structural condition of bridges. The method uses building information modeling (BIM) software to link and analyze data related to the inspection, evaluation, and management of bridges. In the proposed method, an inspector uses a custom software add-in, developed by the authors, to capture information on damage type, amount, severity, and location gathered during bridge inspection. Next, a custom tool in Microsoft Excel evaluates the structural performance and provides load ratings of the inspected bridge. The proposed method was validated through field testing on a case study bridge. Findings from this study suggest that BIM can effectively facilitate the inspection and evaluation of bridges, which may, in the future, enable transportation agencies to more efficiently manage bridge inventories and lead to a more automated practice.

Effect of Existing Structure and FRP Uncertainties on the Reliability of FRP-Based Repair

Externally bonded fiber-reinforced polymer (FRP) has been successfully implemented to repair existing RC structures. Previous studies on the development of a reliability-based design method for externally bonded FRP have considered the additional uncertainties introduced by the FRP, but have relied on descriptions of the existing concrete and reinforcing steel representative of new construction. These descriptions are unlikely to be appropriate for an in-service structure in need of repair. This paper investigates the effects of different levels of uncertainty in existing RC structures and FRP materials on the reliability of repairs designed with ACI 440.2R-08 recommendations. Repairs to restore flexural strength for each beam in an inventory of rectangular and t-shaped beams were designed. The reliability index of these repair designs was evaluated to identify the most influential variables on the reliability of the FRP repairs. When the effects of the existing structure were compared with those of the FRP material, uncertainties related to the existing structure had a much greater impact on the reliability of repair designs. The most significant uncertainties were related to the area of the remaining reinforcing steel and the existing concrete strength.

Uncertainty in Common NDE Techniques for Use in Risk-Based Bridge Inspection Planning: Existing Data

AbstractIn 2009, a joint American Society of Civil Engineers Structural Engineering Institute and American Association of State Highway and Transportation Officials ad hoc group was created to study how current bridge practices could be improved for the future. Among their recommendations was the wider use of nondestructive evaluation (NDE) techniques. Risk-based planning to determine the appropriate inspection frequency, scope, intensity, and methodology would help make the increased time and costs associated with NDE inspections feasible for management budgets. However, a rigorous risk-based approach requires that the accuracy and reliability be quantified for each test. This paper serves as a starting point for quantifying these important variables and identifies the type of information that is still needed. Common NDE techniques were identified, and existing studies were reviewed to identify what data relevant to accuracy and reliability are currently available for these techniques. This review indica...

Evaluation of Pull-Off Tests as a FRP–Concrete Bond Testing Method in the Laboratory and Field

The direct tension pull-off test has gained popularity as a test method used in the laboratory and especially in the field to assess the quality of bond between externally bonded fiber-reinforced polymer (FRP) repair materials and concrete owing to its low cost and simple procedure. However, the small scale and localized nature of the test can lead to high variability in the results. Furthermore, the test does not load the bond in a way that is representative of service conditions. Because of these limitations, satisfactory interpretation of results can be difficult. This paper examines the challenges that may be encountered when analyzing the data obtained during testing, including the high variances. Past research efforts using pull-off tests, and results of recent field and laboratory testing by the authors, are discussed to evaluate the benefits and weaknesses of pull-off tests as a quality control and research tool. The authors conclude that pull-off tests have many drawbacks, and if they are used, great care is needed in their application. It is recommended that if this method is to be used as a quality control procedure in the field, pull-off tests on the concrete alone should be conducted to obtain baseline values, and supplementary tests such as acoustic sounding also be used. For laboratory conditions, it is advised that alternative testing procedures be considered and large sample sizes be used to make statistical validation possible.

Evaluating the Long-Term Durability of Externally Bonded FRP via Field Assessments

AbstractFiber-reinforced polymer composites (FRP) are an attractive repair option for reinforced concrete structures, but whereas laboratory durability tests have indicated that FRP generally performs well in many environments, their long-term performance in field environments is not well understood. This case study describes an effort to collect in situ data about the FRP used to repair a concrete arch bridge 8xa0years after the FRP was originally placed. On-site assessment efforts included inspection for voids between the concrete and FRP using acoustic sounding and thermographic imaging and pull-off tests to check the bond strength. Large debonded regions of FRP were also cut from the structure and tested in tension in the laboratory. Results generally pointed to some level deterioration. Many new voids were found, existing voids had grown, pull-off testing showed weaker bond strengths, and the tensile strengths were quite low compared to design values. However, a lack of initial data make it difficult t...

Best practices to support and improve pavement management systems for low-volume paved roads

ABSTRACT The most important issue in managing low-volume roads (LVRs) is to define standards and practices applied on roads. In recent years, transportation agencies have dealt with considerable challenges for managing LVRs. These challenges include reductions in maintenance budgets; impact of industrial activities; and ineffective treatments applied on paved roads. The Wyoming Technology Transfer Centre (WYT2/LTAP) conducted online surveys as part of a research project conducted jointly with the Colorado Department of Transportation. The objective of the surveys is to document what the transportation agencies, including state departments of transportation (DOTs), are doing to face these challenges. Four online surveys were sent to the TRB LVRs committee, eight DOTs, local governments in Colorado and the material advisory committee in the Colorado DOT. These surveys have an average of 26 questions dealing with pavement management system (PMS) specifications recommended for low-volume paved roads. Seventy-one transportation agencies responded to the survey. This paper summarises the responses to the survey showing innovative programmes, procedures and products that are successfully meeting LVRs pavement management needs.

Influence of Local Wall Variation in the Elastic Properties of Planar Cellular Solids

A numerical model based on one-dimensional cell wall behavior is used to study the influence of changes in the cell wall properties on the global stiffness parameters of two-dimensional open-celled honeycombs. Following validation of results for intact microstructures, cases are considered, including regular and irregular cellular structures, structures with missing/broken cell walls, and structures with cell walls of non-uniform thickness. The influence of each of these flaws or changes in microstructure is quantified, with broken cell walls dominating changes in bulk behavior and varying cell wall thickness resulting in changes to bulk properties that can be considered negligible.

Responses to different types of inquiry prompts: college students’ discourse, performance, and perceptions of group work in an engineering class

ABSTRACT Working in small groups to solve problems is an instructional strategy that allows university students in science, technology, engineering, and mathematics disciplines the opportunity to practice interpersonal and professional skills while gaining and applying discipline-specific content knowledge. Previous research indicates that not all group work prompts result in the same experiences for students. In this study we posed two types of prompts (guided and open) to undergraduate engineering students in a statics course as they participated in group work projects. We measured student discourse, student performance, and perceptions of group work. We found that guided prompts were associated with higher-level discourse and higher performance (project scores) than open prompts. Students engaged in guided prompts were more likely to discuss distribution of labour and design/calculation details of their projects than when students responded to open prompts. We posit that guided prompts, which more clearly articulate expectations of students, help students determine how to divide tasks amongst themselves and, subsequently, jump to higher levels of discourse.

Developing a methodology to evaluate the effectiveness of pavement treatments applied to low-volume paved roads

ABSTRACT A significant number of agencies allocate low funding levels for their low-volume roads (LVRs) as part of their pavement management system (PMS) funding strategies. Although agencies have been applying a number of low-cost treatments, the effectiveness of the applied treatments towards improving pavement performance is not well understood or documented. The application of low-cost treatments on roads has different levels of impact on the pavement performance depending on the initial pavement condition. This study introduces a methodology of evaluating in-practice surface treatments on LVRs. The methodology can be implemented by different transportation agencies using historical data of pavement condition and treatment records. A case study of managing LVRs in Colorado was investigated using the historical PMS data of Colorado Department of Transportation (CDOT). The performance of pavement in the context of fatigue, longitudinal, and transverse cracking was analysed and the results show different trends of common treatment options applied to LVRs. It was concluded that some surface maintenance strategies are effective long-term treatments for fatigue, longitudinal, and transverse cracking. However, the effectiveness of these treatments depends mainly on the initial condition index. The findings of this study permits increased understanding of selected maintenance treatments. An appropriate maintenance strategy was developed including all effective treatments. The comprehensive long-term analysis of road maintenance and costs shows that the proposed maintenance strategy is more cost-effective compared to the current policy followed by CDOT.

Developing Pavement Distress Deterioration Models for Pavement Management System Using Markovian Probabilistic Process

In the state of Colorado, the Colorado Department of Transportation (CDOT) utilizes their pavement management system (PMS) to manage approximately 9,100 miles of interstate, highways, and low-volume roads. Three types of deterioration models are currently being used in the existing PMS: site-specific, family, and expert opinion curves. These curves are developed using deterministic techniques. In the deterministic technique, the uncertainties of pavement deterioration related to traffic and weather are not considered. Probabilistic models that take into account the uncertainties result in more accurate curves. In this study, probabilistic models using the discrete-time Markov process were developed for five distress indices: transverse, longitudinal, fatigue, rut, and ride indices, as a case study on low-volume roads. Regression techniques were used to develop the deterioration paths using the predicted distribution of indices estimated from the Markov process. Results indicated that longitudinal, fatigue, and rut indices had very slow deterioration over time, whereas transverse and ride indices showed faster deterioration. The developed deterioration models had the coefficient of determination (R2) above 0.84. As probabilistic models provide more accurate results, it is recommended that these models be used as the family curves in the CDOT PMS for low-volume roads.