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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.
1

Acoustic Emission Sensing for Crack Monitoring in Prefabricated and Prestressed Reinforced Concrete Bridge Girders

Worley, Robert Lee, II 01 January 2019 (has links)
Prefabricated and pre-stressed reinforced concrete beams and girders are integral components of many highway structures, including those built by rapid construction techniques. Concerns exist regarding the development of cracks during curing, form removal, detensioning, transport, installation, and operation. Non-destructive, Acoustic Emission (AE) sensing techniques have the potential for detecting and locating cracking in prefabricated, pre-stressed concrete girders used as Prefabricated Bridge Elements and Systems (PBES) used in rapid construction practices as part of a Quality Assurance/Quality Control (QA/QC) program. AE sensing records transient elastic waves produced by the release of stored elastic energy resulting in plastic deformations (i.e., crack nucleation and growth) with an array of point sensors. The AE instrument system is relatively portable which can allow for it to be an option for both off-site fabrication QA/QC as well as on-site field QA/QC. This thesis presents a multi-stage research initiative on acoustic emission monitoring of prefabricated and pre-stressed reinforced concrete beams used in highway bridge construction during detensioning, craned removal from formwork and transport to bridge sites, along with supporting laboratory tests and numerical analysis. The specific objectives of this research were to: 1. Identify suitable instruments to monitor pre-stressed and/or post-tensioned concrete girders for cracking activity; 2. Design and develop a reusable instrumentation package; 3. Measure performance and condition of concrete girders during fabrication and transport; and 4. Identify test protocols and possible accept/fix/reject criteria for structural elements based on information from monitoring system. Presented are results from laboratory, full-scale girder fabrication, and transport monitoring, along with overall conclusions and recommendations for future research.
2

Závislost ceny a lhůty výstavby vybraného stavebního objektu na použité technologii / Dependence of a price and a building period of selected construction on the technology

Jandová, Renáta January 2015 (has links)
The thesis focuses on the dependence of price and building period of selected construction on the technology of the certain object. Three different technologies are being compared regarding the supporting structure of the bridge. The first two technologies consider girder prefabs and the third technology involves a monolithic support plate. The technological method no. 1 is implemented through assembling of the girders via conveyor line with the assistance of mobile cranes; the method no. 2, on the other hand, implies the whole assembly from below the bridge also using mobile cranes. The method no. 3 is monolithic – the wooden basis is covered with concrete layer. The dependence of construction time and price is carried out by the comparison of methodologies through budgets, schedules, multi-criteria ratings and economic ratings.

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