1,720,963 research outputs found
Exploring Fiber-Reinforced Polymer Concrete for Accelerated Bridge Construction Applications
No full textThesis (Master's)--University of Washington, 2022The use of prefabricated superstructure elements in bridge construction reduces on-site construction time, improves work-zone safety, and can reduce overall project costs. For prefabricated elements to be used efficiently for accelerated bridge construction (ABC), the precast components, such as deck panels or decked-bulb tees, must be connected quickly on-site, ideally using as little additional material as possible. The use of fiber-reinforced polymer concrete (FRPC) was explored as a closure pour material for bridges to connect adjacent precast superstructure elements. Polymer concretes have been used successfully as a non-structural overlay material in transportation systems for many decades. With the addition of fibers, FRPC displays levels of two critical characteristics, bond and tension strength, that are comparable to other alternatives, such as ultra-high performance concrete (UHPC). While UHPC may still provide the best solution in many instances, FRPC has the advantage of requiring shorter closure windows (approximately 4 hours versus 72 hours for UHPC) due to the very rapid strength gain of the polymer, which could be ideal for overnight construction or rehabilitation projects.
The bond and mechanical properties of FRPC were determined at several temperatures, spanning the range of typical service conditions in western Washington State. Tests were completed measuring the compressive, flexural, and bond strength of FRPC. Then, a central composite rotatable experimental design was utilized to explore the impact of splice length, side cover, bar size, and temperature on bar stress in non-contact splice specimens. The test setup was similar to that completed by the Federal Highway Administration (FHWA) with UHPC.
The results of the testing program indicate that FRPC exhibits significant variation in mechanical properties with temperature, roughly -0.6 %/°F; the development of early compressive, flexure, and bond strengths were very similar, reaching roughly 70% of their 7-day values in 4 hours; and peak bar stresses in non-contact lap splices embedded in FRPC were comparable to UHPC for the embedded lengths tested. Based on the testing results, example joint configurations for connecting precast superstructure elements were developed, enabling the comparison of FRPC with alternative closure pour materials for future ABC projects
Initial Evaluation of Digital Twin Technology and Internet-of-Things Sensors for the Interstate-90 Homer Hadley Floating Bridge
Get PDFThesis (Master's)--University of Washington, 2025The emergence of digital twin technology is set to reshape the management of civil infrastructure by enabling real-time monitoring, predictive maintenance, and data-driven decision-making. Advances in internet-of-things (IoT) sensors, 5G connectivity, and cloud computing allow structural health monitoring systems to collect high-resolution data from diverse sensor types, transmit it in real time, and aggregate it within accessible, cloud-based platforms. These capabilities are particularly valuable for complex structures like floating bridges, which require constant visual inspections and are highly sensitive to dynamic forces and inputs from the environment. This thesis details the design, deployment, and initial evaluation of a “proof-of-technology” digital twin for the Homer M. Hadley (I 90) floating bridge in collaboration with the Washington State Department of Transportation, the University of Washington’s Mobility Innovation Center, and industry partners. The Homer M. Hadley bridge is the only floating bridge in the world that supports light-rail transit, requires many more maintenance and operations decisions than a typical bridge, and has the potential to be uniquely benefitted from the insights that digital twins can provide.
A system of IoT sensors was installed to monitor key structural and environmental parameters, including anchor cable tension, pontoon movement, pontoon freeboard, and temperature. Data was transmitted over the 5G cellular network and integrated into a cloud-based digital twin platform. Additional data, for example, lake level, lake water quality, traffic, and weather data from outside sources were also federated into the system. The digital twin was then used to assess bridge behavior in real-world conditions, focusing on anomaly detection capabilities, usefulness of real-time monitoring, and the feasibility of integrating such a system into existing maintenance programs
Numerical Evaluation of Code Requirements and Nonlinear Performance of Torsionally Irregular Structures
No full textThesis (Ph.D.)--University of Washington, 2025Structures with torsionally irregular configurations – those with non-coincident centers of mass, stiffness, and strength – are vulnerable to amplified seismic demands from twisting modes of response that localize deformation and damage, increasing the likelihood of failure or collapse during strong ground shaking. Despite decades of research, design provisions for torsional irregularity remain inconsistent across international codes and are often based on studies of reduced-order models that may not adequately capture the behavior of multi-story or spatially irregular systems. To address these perceived gaps, this dissertation leverages high-performance computing to investigate the design and behavior of torsionally irregular structures through three interconnected studies: (1) Minimizing superstructure twist in irregular bridges through optimization of structural parameters (2) Evaluation of design provisions in the New Zealand seismic design standard (NZS 1170.5:2004) for the seismic assessment of torsionally irregular buildings, and (3) Improving the seismic performance of torsionally irregular buildings using force-limiting diaphragm connections. The first study investigates geometrically irregular bridges using a validated finite element model of a previously tested reinforced concrete bridge. It evaluates three modification strategies: adjusting column effective heights, altering end fixity conditions, and redistributing superstructure mass, to reduce torsional response. Numerical and optimization-based studies showed that increasing the effective stiffness of columns by reducing their effective height was the most efficient strategy. The study also demonstrated that a small subset of hazard-consistent ground motions could capture the essential behavior required for optimization, providing a practical balance between computational efficiency and accuracy. The second study examines torsionally irregular buildings within the context of the New Zealand seismic design standard (NZS 1170.5:2004). Reinforced Concrete Shear Wall (RCSW) and Steel Special Moment Frame (SSMF) buildings were designed and analyzed using nonlinear time-history simulations of site-specific ground motions derived from the 2022 New Zealand National Seismic Hazard Model. A comparative analysis of the current code provisions and proposed updates by a working task group showed that the proposed updates substantially reduced maximum drift demands and collapse probabilities, especially for highly ductile SSMF systems, while penalizing designs with excessive torsional irregularity. The third study explores the potential of deformable Inertial Force-Limiting Connections (IFLC) to reduce seismic demands in irregular buildings. By replacing conventional rigid diaphragm-to-lateral system links with deformable connections designed to dissipate energy and limit force transfer, the study established rational benchmarks for connection stiffness and strength based on diaphragm design forces and system drift constraints. Results indicated that properly tuned IFLCs can reduce lateral force demands, making them a promising design option for improving the seismic resilience of irregular structures. Overall, the findings of this dissertation improve our understanding of torsionally irregular structural systems through code-level evaluations employing advanced numerical modeling techniques and the examination of innovative connection strategies through numerical optimization. The results provide a rational basis for updating national seismic design standards and highlight the potential of force-limiting methods as a next-generation seismic design tool for irregular structures
High-Early Strength Concrete for Rapid Bridge Deck Repair and Rehabilitation
No full textThesis (Master's)--University of Washington, 2024With an ever-increasing demand for bridge deck rehabilitation due to aging infrastructure and increasing traffic demands, bridge deck overlays are used as a viable economic and environmentally cost-effective solution for prolonging the service life of a bridge. These overlays typically share the same characteristic of fast-setting and high-early strength development to minimize traffic disruptions, however, current methods do not typically address rehabilitation at varying levels of deterioration or make use of expensive non-cementitious materials. This research investigated the use of belitic calcium sulfoaluminate (CSA) cement to determine highest performing mix designs and surface preparations, to aid in the implementation and identification of a cement-based alternative repair material. An extensive experimental testing program resulted in nine slab specimens that were cast, overlayed, bond tested, and evaluated to identify the best performing BCSA mix designs, surface preparations, and admixtures. Various overlay and substrate laboratory specimens were also tested to identify fresh and hardened concrete properties which were essential in understanding overlay-to-substrate compatibility for long-lasting repairs. The results of the testing program indicate that BCSA cements show high potential to be successful in accelerated overlay applications. BCSA cements tested in this studied exhibited fast-setting and rapid strength gain, reaching minimum opening strength thresholds from various state agencies within a day. When compared to the conventional portland cement substrate cast in this study, BCSA cements exhibited much lower drying shrinkage, and no cracks were observed in the overlays cast. Polymer modified BCSA cements exhibited exceptional bond strengths higher than performance criteria specified for ultra-high-performance overlays by Caltrans (>400 psi) and comparable to bond strength requirements for polyester polymer concrete (500 psi). Bond testing results indicate that polymer modifying BCSA cements leads to significant increases in bond strength
Shear Behavior of Macro-Synthetic Fiber-Reinforced Concrete Panels
No full textThesis (Master's)--University of Washington, 2023Macro-synthetic (polypropylene or polyolefin) fibers are often added to concrete mixtures as secondary reinforcement, designed to control shrinkage and temperature cracks. The contribution of these fibers to the strength of structural elements and the interactions and synergies between distributed fiber and deformed bar reinforcement are not well understood. This research investigated the behavior of macro-synthetic fiber-reinforced concrete panels subjected to in-plane shear stresses. Twelve panel specimens were tested using the Panel Element Tester located in the Structure Engineering Testing Laboratory at the University of Washington. The panel specimens varied in their transverse reinforcement ratio (ranging from 0% to 1.1%) and fiber content (ranging from 0% to 0.5%). Additionally, companion specimens were cast and tested alongside each panel to determine material properties, including compressive strength, modulus of elasticity, and flexural toughness and strength. The results of the tests showed that macro-synthetic fibers, at the dosage rates used, were effective at reducing both the average and maximum crack widths observed throughout testing. Generally, the addition of fibers led to finer, more distributed cracking in the panel specimens and no significant change to the panels’ shear strengths. Comparisons to existing empirical shear equations from the literature showed overestimations of shear strength in panels containing no transverse reinforcement and tended toward more accurate estimates as the reinforcement ratio increased. In the larger project, the experimental data that was collected will be used to develop rational design guidelines for the shear strength of members that contain both macro-synthetic fibers and transverse deformed bar reinforcement
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Predicting The Shear Strength of Macro-Synthetic Fiber-Reinforced Concrete
No full textThesis (Master's)--University of Washington, 2024Macro-synthetic fibers are commonly added to concrete mixtures as secondary reinforce- ment to control temperature and shrinkage cracks in concrete flatwork. The fibers limit the width of cracks that develop in the cast concrete, improving durability and longevity. The fibers also improve the tensile behavior of the material. However, the contribution of macro- synthetic fibers towards the strength of structural elements is generally neglected. A re- cent experimental program tested twelve macro-synthetic fiber-reinforced concrete (PFRC) panels subjected to pure shear loading and explored the contribution of macro-synthetic fibers to shear strength when used in combination with conventional deformed bar shear reinforcement. The tests indicated that, for typical fiber contents (≤ 0.5% by volume), macro-synthetic fibers did not decrease the shear capacity of the panels but reduced crack widths at various load levels. The experimental program provided some evidence that macro-synthetic fibers are beneficial for shear loading but was limited in scope and in the levels of the experimental variables that could be tested.To further investigate the influence of macro-synthetic fibers on shear behavior, a para- metric study was performed using finite element models to extend the experimental results and explore combinations of parameters that were not tested experimentally. A modeling approach was calibrated using the experimental panel data, where a concrete tension soften- ing model was incorporated to capture the strength contribution of the fibers. The modeling approach was validated against a database of PFRC beams from the literature, which was compiled as part of this research. The modeling approach was then used to conduct a
parametric study, exploring the monotonic pure shear strength of PFRC panels with over 250 combinations of fiber contents, transverse reinforcement ratios, and concrete compres- sive strengths. The results of the parametric study indicated that macro-synthetic fibers effectively reduced crack widths and enhanced shear strength, depending on the transverse reinforcement ratio and fiber content. Greater benefits were observed for lower transverse reinforcement ratios (≤ 0.25%) and higher fiber contents (> 1.0%), exhibiting slightly dif- ferent trends for the different concrete compressive strengths.
The ability of existing empirical equations in model codes and in the literature to predict the shear strength of PFRC structural elements was also evaluated. Most current design codes neglect the contribution of macro-synthetic fibers to the shear strength of structural elements, which resulted in significant underestimation of shear strength. Several empirical equations from the literature provided more reasonable estimates of shear strength for both PFRC beams and panels and were used to propose a fiber-reinforcement term that would modify current code-based shear strength prediction equations. Recognizing the structural benefits of macro-synthetic fibers would increase their use and would lead to more durable and resilient reinforced concrete structures
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