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Research Study to Inform Strut-and-Tie Design and Guidance
Research Study to Inform Strut-and-Tie Design and Guidance
Research Assistant: Mariah Boler
Given contemporary understandings and recent research, there is a need to update the Arizona Department of Transportation (ADOT) Bridge Design Guidelines to include the latest state-of-practice and provide guidance to designers as to when and where the strut-and-tie method (STM) is most advantageous. The objective of this project is to research, develop, and implement criteria for updating and improving the Bridge Design Guidelines and corresponding examples.
Evaluation of Minimum Web Reinforcement Requirements for Slender and Non-Slender Beams
Evaluation of Minimum Web Reinforcement Requirements for Slender and Non-Slender Beams
Research Assistant: Russell Collins
Prescriptive shear requirements from ACI 318 (2019), AASHTO LRFD (2020), and the fib Model Code (2010) include a minimum web reinforcement requirement. In general, slender beams require a minimum area of web reinforcement equal to 0.08% of the cross-section, while non-slender beams require up to 0.30%, or roughly three times more than the slender beam requirement. This investigation aims to evaluate the discrepancy between these requirements in terms of the strength and serviceability behavior of experimental test data. The aim is accomplished through an analysis of existing and peer-reviewed databases. Given the context of this investigation and available data, the results show that the minimum web reinforcement needed for strength is consistent with code requirements for slender beams but not deep beams, and the minimum web reinforcement needed for serviceability behavior is consistent with code requirements for non-slender but not slender beams. Thus, the prescriptive web reinforcement requirements for slender and non-slender beams do not appear to be derived from the same criteria. The minimum web reinforcement requirement for slender beams is likely derived based on these members achieving their predicted strength, while the requirement for non-slender beams is likely derived based on the width of in-service cracks.
Click here to access an article in Transportation Research Record
Creating Practice-Ready Bridge Engineers through Anchored Learning, Principal Investigator.
Creating Practice-Ready Bridge Engineers through Anchored Learning, Principal Investigator.
Sponsor: Federal Highway Administration (FHWA)
Research Assistant: Davis Ray
Traditionally, undergraduate engineering students view their course work as a necessary means toward a degree. At which point, they enter the workforce and learn what it “really takes” to be an engineer. They do not necessarily view the knowledge acquired as the important means toward the foundational theoretical and mathematical principles needed to be an engineer. Thus, there is a need for an engineering program that provides skills which are more likely to be transferred to engineering practice.
In response, the goal of this project is to assess "Anchored Instruction" as a pedagogical approach for modifying the course of study within an existing undergraduate civil engineering curriculum such that fundamental engineering knowledge is better transferred between theory and practice. The Anchor is a highly contextualized scenario or case that would realistically be solved in practice by a bridge designer. Students use the details from the case or Anchor to apply theoretical concepts. This project will anchor Statics, Mechanics of Materials, and Structural Analysis to a bridge analysis Anchor, and Reinforced Concrete and Structural Steel to a bridge design Anchor. An additional Bridge Design elective course will be provided as a means of measuring students’ ability to ‘transfer’ the theoretical knowledge attained in their foundational courses.
Click here to access article in ASPIRE. The Concrete Bridge Magazine
Proof Testing of a Shear Deficient Bent Cap.
Proof Testing of a Shear Deficient Bent Cap.
Stakeholder: Kiewit Infrastructure Engineers
An existing 58-year-old viaduct was removed and replaced between 2020 and 2021. Many of the bent caps supporting this viaduct exhibited wide shear cracking. Though the viaduct’s performance had been satisfactory throughout its lifetime, concerns were raised that construction disturbances required for the staged construction of the new roadway might compromise their safety. Given that this highway carries approximately 145,000 vehicles per day, closing it completely to effect these changes was an extremely undesirable solution.
In response, the Design-Builder proof tested the bent cap that caused the greatest concern and used these results to improve the certainty of the calculated capacity of all the bent caps. The results of the proof test were used along with the requirements of the AASHTO Manual for Bridge Evaluation to assess the capacity of the other bent caps supporting the viaduct.
The structure was loaded by placing ballasted trucks over the bent cap in question. The change in width of the widest shear crack, deflection, and strain at the bottom of the cap were monitored during testing. Upon conclusion of the test, the capacity of the bent cap was determined to be greater than the required demand. The results were used to show that most bents supporting the viaduct had adequate strength. For a small number needing strengthening, the results were used to develop a simpler and more straightforward repair procedure than would have been required without the findings of the proof test.
Click here to access an article in Transportation Research Record
Arizona Tri-University Transportation Research Collaboration, Co-Principal Investigator.
Arizona Tri-University Transportation Research Collaboration, Co-Principal Investigator.
Sponsor: Arizona Board of Regents (ABOR)
Research Assistant: Meg Stevens
Transportation is critical to the economic success and growth of Arizona, the Southwest region, and the nation as a whole. In 2016, the three state universities championed a research program, sponsored under the Arizona Board of Regents’ Innovation Fund (RIF), to look at broad and crosscutting issues related to an important Arizona Department of Transportation (ADOT) priority project on the I-10 Western Freight Corridor. The Year 1 project aimed to transition Interstate-10 into a modern freight corridor to improve the safety, mobility, environmental, and economic viability of the system and the affected states.
For Year 2 of the ABOR RIF project, Team 3 proposes to develop structural inputs to resilience assessment in the face of confounding and additive factors in our changing natural environment. Responses under these combinations of structural inputs are largely unknown, but present major challenges for the public and roadway managers. For example, how does the combination of increased stream flow, extreme heat, and excessive loading impact the structural integrity of a bridge; how can we analyze and respond to these additive factors; when should the user elect for an alternative route; and when should the manager impose restrictions on use? Technologies are emerging with great potential to provide infrastructure managers and roadway users details on the changing conditions of existing infrastructure, and to inform transportation management systems about the impact of these factors. The specific tasks of this project will include a combination of sensing (e.g., pavement integrity in different conditions, bridge scour prediction, and bridge condition photogrammetry/structural health monitoring), modeling/simulation (e.g., site-specific hydraulic modeling and meso-scale traffic modeling), and systems-level analysis (e.g., corridor-level adaptation and resilience assessment). The resulting work will showcase the combined strengths of the three universities in the area of infrastructure resilience and position the Arizona universities to be leaders in this area of research in the future.
Click here to access to article in ASCE's Practice Periodical on Structural Design and Construction
Research Initiation: Reshaping Engineering Classroom Norms to Diversify the Profession, Principal Investigator.
Research Initiation: Reshaping Engineering Classroom Norms to Diversify the Profession, Principal Investigator.
Sponsor: National Science Foundation
Co-PI: Ron Gray, PhD. NAU Center for Science Teaching and Learning
Ph.D. Candidate: Allison Gray
By some estimates, roughly half the students that graduate with an engineering degree end up employed in a non-engineering field. Attempts to fix this "leaky pipeline" rarely address the fact that the culture (rather than academics) may be driving students away. Throughout their careers, students ask themselves, "What are the attributes inherent in being an engineer?" Often, the answer to that question is defined by outdated engineering ways of knowing, thinking, and doing. Such lack of inclusivity, especially when college students are forming their professional identity, has a significant impact on their interest and the appeal of an engineering occupation. To better expand the profession, there is a need to identify and understand the impact of social-engineering norms in university programs and in the profession. Reshaping Norms serves to address this need by studying the impacts of a series of classroom interventions. The focus of Reshaping Norms is to identify and reshape the norms that cause a student to form (or not form) an identity of themselves as an engineer. As a society, we must encourage the creation of new perspectives because the ability to innovate and exploit niche markets is better served by people who bring a wide-range of diverse experiences to the profession. Similarly, the ability of the public to make well-informed decisions is better served by a diverse profession actively engaged within their communities. This project serves to address these needs by broadening the characterization of engineering identity and catalyzing the engagement of students with their communities.
Use of Photogrammetry to Assess the Condition of Structural Concrete, Advisor.
Use of Photogrammetry to Assess the Condition of Structural Concrete, Advisor.
Sponsor: NAU Intern-2-Scholar (I2S) Program.
Research Assistant: Sabrina Ballard
The purpose of this study is to validate the use of photogrammetry for determining strains and crack widths. This will be accomplished by loading a 6x6x18 inch concrete block and comparing strain measurements calculated from photogrammetry to those of strain gauges or extensometers. This project also compares crack width measurements from high-resolution orthorectified photographs to those obtained using a crack comparator card or microscope.
Serviceability Behavior of Reinforced Concrete Discontinuity Regions, Principal Investigator.
Serviceability Behavior of Reinforced Concrete Discontinuity Regions, Principal Investigator.
Sponsors: NAU Faculty Grants Program. Concrete Research Council. Portland Cement Association.
Research Assistant: Jessica Kettelkamp
The objective of this study is to create a procedure for predicting the serviceability behavior of reinforced concrete discontinuity regions. This will be accomplished by testing 12 deep beams and 6 "complex" discontinuity regions and correlating service-level maximum crack width and total area of cracked surface to the strain energy estimated within the elements of a strut-and-tie model.
Minimum Crack Control Reinforcement for Fiber-Reinforced Deep Beams, Principal Investigator.
Minimum Crack Control Reinforcement for Fiber-Reinforced Deep Beams, Principal Investigator.
Sponsor: Federal Highway Administration Dwight D. Eisenhower Transportation Fellowship Program.
Research Assistant: Alejandra Quesada
The objective of this study is to quantify the steel fibers necessary to supplement the minimum required amount of web reinforcement for deep beams. This will be accomplished by testing nine 12 x 18-inch specimens at a shear span-to-depth ratio of 1.8. Experimental variables will include the volumetric percentage of steel fibers and the percentage of transverse web reinforcement. The rate of growth of the crack widths for specimens with and without fibers will be compared with one another and this relationship will be used to quantify their serviceability performance.
Bearing Strength of Triaxially Confined Fiber-Reinforced Concrete, Principal Investigator.
Bearing Strength of Triaxially Confined Fiber-Reinforced Concrete, Principal Investigator.
Sponsor: NAU Faculty Grants Program.
Research Assistant: Tanner Wytroval
The purpose of this study is to examine the influence of steel fiber reinforced concrete (SFRC) on the strength of triaxially confined bearing areas. To accomplish this goal, twenty-four 12 x 24 in. cylindrical specimens were loaded to failure through 6- in. (150 mm) and 3-in. (75-mm) diameter bearing plates. Experimental variables included transverse reinforcement ratios ranging between 0.0 and 0.8 percent, and steel fiber dosages between 0.0 and 1.5 percent by volume.
Technical Consultation on Rehabilitation of Historic Masonry Ponds, Pipe Spring National Monument , Principal Investigator.
Technical Consultation on Rehabilitation of Historic Masonry Ponds, Pipe Spring National Monument , Principal Investigator.
Sponsor: National Park Service.
The objective of this study is to conduct a structural condition assessment of two historic masonry ponds that contain water from nearby springs at Pipe Spring National Monument (PISP), and develop repair and modification concepts. To assist with future funding decisions, concepts are accompanied with an estimate of the probable construction cost and service life.
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