Chris Ramseyer

Teachers in an Interdisciplinary Learning Community: Engaging, Integrating, and Strengthening K-12 Education

This study examines the inputs (processes and strategies) and outputs (perceptions, skill development, classroom transfer, disciplinary integration, social networking, and community development) of a yearlong, interdisciplinary teacher learning and development experience. Eleven secondary math and science teachers partnered with an interdisciplinary team of university engineering mentors in a yearlong engineering education and project implementation program. It consisted of a 6-week on-site resident professional development and collaboration experience, with an ongoing support and follow-up including digital systems. Mixed-method, multisource data indicate that teachers engaged with motivations combining personal, intrinsic interest and classroom integration goals. They formed and sustained an active community of learning and practice that supported their success, on-site and through classroom integration, thereby promoting innovations. Teachers reported positive perceptions throughout the program and demonstrated significant, productive trajectories of change-over-time. Teachers learned and transferred task-specific engineering and scientific skills, as well as more general inquiry-based pedagogical strategies to their secondary classrooms.

Composite Flexural Behavior of Full-Scale Concrete-Filled Tubes without Axial Loads

Most prior experimental research on the composite behavior of concrete-filled tubes (CFTs) in flexure has been performed using minimodels. The conclusions that have been reached based on the prior research stipulate that the interaction between the concrete and the steel is maximized by steel tube walls confining the concrete, rendering the addition of shear connectors unnecessary. The goal of the current study is to examine the composite flexural behavior of full-scale CFTs, which could be used in actual construction. Four, full-scale, 20-ft- (6-m)-long simple-supported CFT beams were tested under four-point loads. Two were rectangular with a width of 12 in. (305 mm) and the other two beams were circular with a diameter of 18 in. (457 mm). Load, deflection, steel strain, and concrete movement were digitally recorded, and the concrete cracks in each section were mapped and photographed. Test results showed that composite action was improved by shear connectors particularly for circular CFT beams and that the AISC nominal moment capacity prediction was not conservative for circular CFT beams without shear connectors.

Development of an Axial Load Capacity Equation for Doubly Symmetric Built-Up Cold-Formed Sections

AbstractThis work aims to develop an axial load capacity equation for doubly symmetric built-up cold-formed sections with a sufficient number of intermediate, symmetrical connections. A numerical parametric study involving a total of 360 different configurations was conducted, and the numerical results were compared with the experimental data and specifications from the American Iron and Steel Institute (AISI). In this process, the axial load capacities and failure modes, which were influenced by out-of-straightness and out-of-flatness, were thoroughly investigated. To address the issues of an unnecessarily complicated AISI specification for doubly symmetric members subject to distortional buckling, a simple and reliable axial load capacity equation was developed based on a regression analysis of a three-dimensional surface fitting and calibration with the experimental data. This proposed equation exhibited good agreement with the numerically simulated and experimentally measured capacities, while simulta...

Early-Age Properties of Polymer Fiber-Reinforced Concrete

The cracking problem in concrete is widespread and complex. This paper reviews the problem and focuses on those parts of the problem that are more readily solved. Polymer fibers are shown to have promise in several important areas of the cracking problem. To investigate one of these areas of the cracking problem more completely, an experimental research program focusing on the early-age properties of fibers was carried out. This study researched the properties of four polymer fibers; two of the fibers were macrofibers, and two were microfibers. Each fiber was tested at several dosage rates to identify optimum dosage levels. Early-age shrinkage, long-term shrinkage, compressive strength, and tensile strength were investigated. Long-term shrinkage and strength impacts from the polymer fibers were minimal; however, the polymer fibers were shown to have a great impact on early-age shrinkage and a moderate impact on early-age strength.

X-ray-induced acoustic computed tomography with an ultrasound transducer ring-array

The objective of this study is to develop and test a unique X-ray-induced acoustic computed tomography system that combines the advantages of high X-ray imaging contrast and high ultrasonic spatial resolution. The system features a 5 MHz 128-element ultrasound transducer ring-array formed into a full circular aperture. A parallel data receiver, which consists of a dedicated 128-channel preamplifier and a 128-channel data acquisition module, provides full tomographic imaging at a speed of up to 25 frames per second. Details of the system design and calibration are presented, along with the characteristic results of the imaging resolution. The tomographic imaging performance is demonstrated through images of a phantom with a spatial resolution up to 138 μm. The study results indicate that this imaging device and the methodology provide a rapid and high resolution approach for the dynamic imaging of information, and it may have the potential for becoming a promising noninvasive imaging modality to be used in...

Background to multi-scale modelling of unbonded Post-Tensioned concrete structures

Finite element analyses of unbonded Post-Tensioned (PT) concrete structures were carried out with a focus on the modelling of unbonded tendons embedded in the concrete. Two modelling approaches were studied to simulate unbonded conditions using the software package ABAQUS. The first approach was based on contact techniques, which reflect the true physical condition. The other approach used a multiple-spring system that provides more flexibility in modelling and robustness in convergence issues. First, this paper presents comparative results from those two approaches. Subsequently, more detailed analytical studies are described that adopt the spring system for modelling of unbonded PT concrete structures. The analytical results show a reasonably good agreement with experimental results and verify the effectiveness of the spring system approach that could be used for future studies of unbonded PT concrete structures.

Designing and evaluating a STEM teacher learning opportunity in the research university

This study examines the design and evaluation strategies for a year-long teacher learning and development experience, including their effectiveness, efficiency and recommendations for strategic redesign. Design characteristics include programmatic features and outcomes: cognitive, affective and motivational processes; interpersonal and social development; and performance activities. Program participants were secondary math and science teachers, partnered with engineering faculty mentors, in a research university-based education and support program. Data from multiple sources demonstrated strengths and weaknesses in design of the programs learning environment, including: face-to-face and via digital tools; on-site and distance community interactions; and strategic evaluation tools and systems. Implications are considered for the strategic design and evaluation of similar grant-funded research experiences intended to support teacher learning, development and transfer.

Nonlinear buckling of built-up cold-formed sections

An extensive numerical analysis was conducted to investigate the nonlinear buckling of built-up cold-formed sections. This paper presents the calibration of nonlinear finite element models to handle nonlinear buckling behaviour of cold-formed steel sections with geometrically unstable configurations. The two nonlinear finite element packages ANSYS and ABAQUS were used to validate 265 experimental tests. Two different numerical schemes (implicit static and explicit dynamic) under various iterative and non-iterative solution techniques, including Newton-Raphson, Arc-Length, Riks, and Central-Difference integration methods, were adopted to produce reliable solutions. Overall, the numerical analysis estimated the experimental results reasonably well with an adjustment factor of 0.88.

Sulfate resistance of calcium sulphoaluminate cement

Abstract The resistance to chemical sulfate attack was tested for cements containing various amounts of tricalcium aluminate (C3A) and compared to that of calcium sulphoaluminate-belite cement containing no detectable amount of C3A. The six materials tested included a portland Type I (11% C3A), Type II (6% C3A), a Type V (0.5% C3A), and a rapid setting calcium sulphoaluminate (CSA) cement (0% C3A). In addition, two intermediate blends (0.4 and 5.0% C3A) were tested by combining these portland cements with shrinkage compensating CSA cement. Mortar cubes were immersed for two years in a solution containing high concentrations of sodium and sodium/potassium sulfate. Degradation of the mortar cubes was assessed qualitatively via visual observation and quantitatively through measurement of weight change. The magnitude of the degradation by sulfate attack was found to correlate well with C3A content as measured by X-ray diffraction, with Type I portland sustaining the heaviest damage and the CSA rapid setting cement remaining essentially unaffected by the prolonged exposure to the highly sulphated environment.

High-Performance Concrete Designed to Enhance Durability of Bridge Decks: Oklahoma Experience

AbstractBridges are a vital link to the nation’s mobility and prosperity, and those bridges with inadequacies will need to be repaired or replaced as soon as possible. High-performance concrete (HPC) could be the most economical solution. What typically distinguishes HPC from conventional concrete (CC) is the wide variety of cements, supplementary cementitious materials, aggregates, chemical admixtures, and fibers in use. The purpose of this research project was to demonstrate the use of HPC in bridge decks in Oklahoma. HPC mixtures were designed with an optimum blend of three aggregates. With less voids between aggregate particles, the HPC mixtures contained less cement paste, approximately 24% by volume. Examined more than one year after construction, crack densities were less on HPC bridge decks than CC bridge decks. HPC mixtures with fly ash exhibited the best potential durability with crack densities less than 0.1  m/m2. The addition of fibers did not have an effect on crack density.