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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Performance Analysis and Modeling of Pavements with a Cold Central Plant Recycled Base under Accelerated Loading Testing

Zimmerman, Cory Tyler 18 September 2017 (has links)
Cold Central Plant Recycling (CCPR) has been used by many state highway agencies to save material, money, time, and energy in pavement construction and rehabilitation. The objectives of this thesis were to: (1) perform an instrumented verification analysis, (2) evaluate the response and performance of two pavement configurations with a CCPR base layer through accelerated pavement testing (APT), and (3) construct models using mechanistic-empirical pavement design software for comparison with the APT results. The pavement configurations featured a 5-inch CCPR mixture with either a 3-inch or 1.5-inch SM-9.5D surface mixture. Each section was instrumented with strain gauges, pressure cells, and thermocouples. A heavy vehicle simulator (HVS) was used to load three replicate test sections in each lane, with the temperature controlled at 39°C at a depth of 1.5 inches. Results from the instrument verification analysis showed that the strain gauges and pressure cells used in the experiment recorded pavement responses with a high degree of repeatability. In addition, the loading condition variables (speed, wheel load, and tire inflation pressure) affected the response following the expected trends and did not affect the repeatability of the instruments. The average CV of all strain gauge and pressure cell signals was approximately 0.009 or 0.9%, and 0.004 or 0.4%, respectively. In terms of the rutting comparison, the sections with the 3-inch surface layer outperformed the sections with the thinner 1.5-inch surface layer. However, the age of the pavement at the start of testing significantly affected the rutting performance. After adjusting for the pavement age at the time of testing, the section with the thicker surface showed approximately half of the rutting of the section with the thinner surface. The results from preliminary ME Design analysis indicate that the software cannot model the studied APT sections using the default material properties and calibration factors available at the time of analysis. In particular, the software does not seem to be prepared to model the CCPR materials. / Master of Science
12

Innovative Modular High Performance Lightweight Decks for Accelerated Bridge Construction

Ghasemi, Sahar 13 November 2015 (has links)
At an average age of 42 years, 10% of the nation’s over 607,000 bridges are posted for load restrictions, with an additional 15% considered structurally deficient or functionally obsolete. While there are major concerns with decks in 75% of structurally deficient bridges, often weight and geometry of the deck further limit the load rating and functionality of the bridge. Traditional deck systems and construction methods usually lead to prolonged periods of traffic delays, limiting options for transportation agencies to replace or widen a bridge, especially in urban areas. The purpose of this study was to develop a new generation of ultra-lightweight super shallow solid deck systems to replace open grid steel decks on movable bridges and as well serve as a viable alternative in bridge deck replacements across the country. The study has led to a lightweight low-profile asymmetric waffle deck made with advanced materials. The asymmetry comes from the arrangement of primary and secondary ribs, respectively perpendicular and parallel to the direction of traffic. The waffle deck is made with ultrahigh performance concrete (UHPC) reinforced with either high-strength steel (HSS) or carbon fiber reinforced polymer (CFRP) reinforcement. With this combination, the deck weight was limited to below 21 psf and its overall depth to only 4 inch, while still meeting the strength and ductility demands for 4 ft. typical stringer spacing. It was further envisioned that the ultra-high strength of UHPC is best matched with the high strength of HSS or CFRP reinforcement for an efficient system and the ductile behavior of UHPC can help mask the linear elastic response of CFRP reinforcement and result in an overall ductile system. The issues of consideration from the design and constructability perspectives have included strength and stiffness, bond and development length for the reinforcement, punching shear and panel action. A series of experiments were conducted to help address these issues. Additionally full-size panels were made for testing under heavy vehicle simulator (HVS) at the accelerated pavement testing (APT) facility in Gainesville. Detailed finite element analyses were also carried out to help guide the design of this new generation of bridge decks. The research has confirmed the superior performance of the new deck system and its feasibility.
13

Accelerated Testing of Pavement with Embedded Dynamic Wireless Power Transfer Components

Oscar Moncada (17378296) 14 November 2023 (has links)
<p dir="ltr">This thesis investigates the embedment of Dynamic Wireless Power Transfer (DWPT) components within two pavement test sections, aiming to evaluate their mechanical and thermal responses. The integration of DWPT components into the pavement structure, while enabling dynamic power delivery to EVs, alters the conventional geometric design of a typical pavement, potentially influencing their short-term and long-term durability and integrity. Hence, to ensure the integrity and efficiency of both the embedded system and the surrounding structure, it is essential to understand how integrating these components influence the pavement's performance.</p><p dir="ltr">Conducted at the Accelerated Pavement Testing (APT) facility of the Indiana Department of Transportation (INDOT), the study evaluates over the course of 25,000 APT traffic passes, the mechanical and thermal responses of both, a flexible and rigid pavement test section. Each test section features a Charging Unit (CU), a concrete slab upon which the DWPT components are placed. The construction of the flexible pavement involved milling down 2 in. of the existing pavement surface, while the rigid pavement required complete demolition of the existing pavement. The flexible pavement’s CU is composed of Class A concrete and the rigid pavement's CU features magnetizable concrete, a type of concrete composed of ferrite particles embedded in a cement matrix. Among the two pavement sections, only the rigid pavement exhibited visible distress, identified as a mid-panel crack. Several factors contributed to the crack formation, including inadequate adhesion between concrete interfaces, concrete mix segregation, material variations, construction issues, and nonuniform load distribution. The manual construction procedures, which were employed to prevent disrupting the embedded DWPT components and sensor instrumentation, and the one-week gap between casting the CU and the surrounding slab might have further influenced the adhesion strength of the rigid pavement section.</p><p dir="ltr">By examining the construction techniques employed, challenges encountered, and resulting behavior of both pavement test sections, this study provides insights into the construction and performance implications of DWPT component integration into pavements, as evidenced by the responses observed in the test sections. This thesis thereby contributes to the ongoing research efforts on investigating the impact such integration has on the surrounding structure's integrity.</p>

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