• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • 1
  • Tagged with
  • 4
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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

Wind tunnel test for guyed mast dynamic characteristics under wind loads

Zhu, Ningli 03 December 2007
An experimental wind tunnel study on the dynamic response of a 300 m tall guyed telecommunication mast under various wind loads was undertaken at the Boundary Layer Wind Tunnel Laboratory (BLWTL) in the University of Western Ontario, London, Canada. Although the dynamic response of guyed masts subjected to turbulent wind loads has been routinely analyzed using a number of numerical models, typically in the frequency domain, limited experimental verification of the dynamic analysis results has been performed. Full-scale measurements, where available, have proven to be difficult to correlate with analytical models due to the tremendous uncertainty inherent in field measurements. As a result, the need for systematic validation of existing analytical models remains.<p>In this investigation, a representative 300 m tall guyed telecommunication mast has been designed and modeled to an appropriate scale. Based on Canadian Standard CSA S37-01, and an empirical study on 41 existing guyed masts, the 300 m tall guyed mast was designed using wind load conforming to representative Canadian climate data obtained from National Building Code of Canada (NBCC 1995). Appropriate properties for the dynamically scaled full aeroelastic model were derived from the 300 m tall prototype guyed mast, which was intended to represent a realistic guyed mast for broadcasting applications in Canada.<p>The wind tunnel test of the guyed mast model was carried out in both open country and over water exposures, simulating medium and low turbulence flow conditions, respectively. Dynamic response characteristics measured during the wind tunnel tests have been analysed and summarized, including dynamic displacements, bending moments, response spectra and peak factors, as well as natural frequencies, mode shapes and structural damping. Comparisons have been made with predictions obtained from an existing frequency domain analysis model. <p>The wind tunnel test results show that good agreement was generally achieved between the frequency domain analytical model and the wind tunnel model with respect to both the magnitude and distribution of the monitored responses. It was found that measured dynamic bending moments were distributed in a fairly uniform manner over the mast height, and that mean (static) bending moments exhibit large variations, along with near-zero response zones at points of contraflexure. It was also found that nonlinear damping effects, associated with vibrations of the highly slackened leeward guys on the upper levels of the mast, may be beneficial in reducing dynamic mast displacements. <p>The spectrum studies indicated that lowest modes were dominated by large guy movements at top guy level and small mast movements, the middle modes were characterized by coupled effects between the guyed cables and mast, meanwhile the highest modes involved significant mast movements with little guy vibration. It is evident that the top of the mast displacement are dominated by the first and second modes.
2

Wind tunnel test for guyed mast dynamic characteristics under wind loads

Zhu, Ningli 03 December 2007 (has links)
An experimental wind tunnel study on the dynamic response of a 300 m tall guyed telecommunication mast under various wind loads was undertaken at the Boundary Layer Wind Tunnel Laboratory (BLWTL) in the University of Western Ontario, London, Canada. Although the dynamic response of guyed masts subjected to turbulent wind loads has been routinely analyzed using a number of numerical models, typically in the frequency domain, limited experimental verification of the dynamic analysis results has been performed. Full-scale measurements, where available, have proven to be difficult to correlate with analytical models due to the tremendous uncertainty inherent in field measurements. As a result, the need for systematic validation of existing analytical models remains.<p>In this investigation, a representative 300 m tall guyed telecommunication mast has been designed and modeled to an appropriate scale. Based on Canadian Standard CSA S37-01, and an empirical study on 41 existing guyed masts, the 300 m tall guyed mast was designed using wind load conforming to representative Canadian climate data obtained from National Building Code of Canada (NBCC 1995). Appropriate properties for the dynamically scaled full aeroelastic model were derived from the 300 m tall prototype guyed mast, which was intended to represent a realistic guyed mast for broadcasting applications in Canada.<p>The wind tunnel test of the guyed mast model was carried out in both open country and over water exposures, simulating medium and low turbulence flow conditions, respectively. Dynamic response characteristics measured during the wind tunnel tests have been analysed and summarized, including dynamic displacements, bending moments, response spectra and peak factors, as well as natural frequencies, mode shapes and structural damping. Comparisons have been made with predictions obtained from an existing frequency domain analysis model. <p>The wind tunnel test results show that good agreement was generally achieved between the frequency domain analytical model and the wind tunnel model with respect to both the magnitude and distribution of the monitored responses. It was found that measured dynamic bending moments were distributed in a fairly uniform manner over the mast height, and that mean (static) bending moments exhibit large variations, along with near-zero response zones at points of contraflexure. It was also found that nonlinear damping effects, associated with vibrations of the highly slackened leeward guys on the upper levels of the mast, may be beneficial in reducing dynamic mast displacements. <p>The spectrum studies indicated that lowest modes were dominated by large guy movements at top guy level and small mast movements, the middle modes were characterized by coupled effects between the guyed cables and mast, meanwhile the highest modes involved significant mast movements with little guy vibration. It is evident that the top of the mast displacement are dominated by the first and second modes.
3

Stiebai su kombinuotomis atotampomis, jų įtempių ir deformacijų analizė bei reguliavimas / Masts with combined guys: analysis and control of stress and deformation

Jatulis, Donatas 14 August 2008 (has links)
Disertacijoje sprendžiama telekomunikacinių stiebų efektyvumo problema. Tyrimo objektas – statiškai apkrauti naujos konstrukcijos stiebai su kombinuotomis atotampomis. Darbe išanalizuota šiuolaikinių stiebų konstrukcinės formos ir skaičiavimo metodai. Nagrinėjama sukurta stiebo su kombinuotomis atotampomis konstrukcija, kurioje vietoj įprastųjų siūloma taikyti kombinuotas atotampas. Disertacijoje šiems stiebams skaičiuoti pateikta inžinerinė skaičiavimo metodika. Pateikti naujo stiebo, veikiamo statinių apkrovų, elgsenos analizės skaitinių ir eksperimentinių laboratorinių tyrimų rezultatai. Stiebo su kombinuotomis atotampomis kamieno lenkiamiesiems momentams reguliuoti darbe siūloma taikyti parengtą stiebų komponavimo metodiką. Šių stiebų efektyvumui nustatyti pateikti gretinamieji tyrimai su įprastos sandaros stiebais. Disertaciją sudaro bendroji darbo charakteristika, 5 skyriai, pagrindiniai darbo rezultatai ir išvados, literatūros sąrašas. / Тhe dissertation deals with the problem of telecommunication masts efficiency. The subject of research – masts of a new structure with combined guys under static loads. The study deals with constructive forms and analysis methods of up-to-date masts. It analyses into a created structure of the mast, wherein it is suggested to apply combine guys instead of the ordinary ones. Engineering guyed masts with combined guys static analysis method is given this research. The numerical and experimental laboratory assay of a new mast under static loads behaviour is given. It is proposed in the study to apply a worked out composing method of masts with combined guys to control the bending moments of shaft. Compared research results are given to measure efficiency of these masts against masts of an ordinary structure. The dissertation includes a general characteristic of study, five chapters, main results and conclusions, list of references.
4

Masts with combined guys: analysis and control of stress and deformation / Stiebai su kombinuotomis atotampomis, jų įtempių ir deformacijų analizė bei reguliavimas

Jatulis, Donatas 14 August 2008 (has links)
Тhe dissertation deals with the problem of telecommunication masts efficiency. The subject of research – masts of a new structure with combined guys under static loads. The study deals with constructive forms and analysis methods of up-to-date masts. It analyses into a created structure of the mast, wherein it is suggested to apply combine guys instead of the ordinary ones. Engineering guyed masts with combined guys static analysis method is given this research. The numerical and experimental laboratory assay of a new mast under static loads behaviour is given. It is proposed in the study to apply a worked out composing method of masts with combined guys to control the bending moments of shaft. Compared research results are given to measure efficiency of these masts against masts of an ordinary structure. The dissertation includes a general characteristic of study, five chapters, main results and conclusions, list of references. / Disertacijoje sprendžiama telekomunikacinių stiebų efektyvumo problema. Tyrimo objektas – statiškai apkrauti naujos konstrukcijos stiebai su kombinuotomis atotampomis. Darbe išanalizuota šiuolaikinių stiebų konstrukcinės formos ir skaičiavimo metodai. Nagrinėjama sukurta stiebo su kombinuotomis atotampomis konstrukcija, kurioje vietoj įprastųjų siūloma taikyti kombinuotas atotampas. Disertacijoje šiems stiebams skaičiuoti pateikta inžinerinė skaičiavimo metodika. Pateikti naujo stiebo, veikiamo statinių apkrovų, elgsenos analizės skaitinių ir eksperimentinių laboratorinių tyrimų rezultatai. Stiebo su kombinuotomis atotampomis kamieno lenkiamiesiems momentams reguliuoti darbe siūloma taikyti parengtą stiebų komponavimo metodiką. Šių stiebų efektyvumui nustatyti pateikti gretinamieji tyrimai su įprastos sandaros stiebais. Disertaciją sudaro bendroji darbo charakteristika, 5 skyriai, pagrindiniai darbo rezultatai ir išvados, literatūros sąrašas.

Page generated in 0.075 seconds