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Wind Flow Induced Vibrations of Tapered Masts

Bani Hani, Ahmad
http://rave.ohiolink.edu/etdc/view?acc_num=csu1243389014

Abstract Details

2009, Master of Science in Mechanical Engineering, Cleveland State University, Fenn College of Engineering.
Structural dynamic analyses of elongated masts subjected to various wind speeds are presented in this work. The masts are modeled as vertically supported cantilever beams,with one end fixed to the ground, and the other end free. The external excitation forces acting of the masts are the results of vortex shedding represented by a sinusoidal time dependent functions. The frequencies of these sinusoidal functions are dictated by the Strouhal numbers associated of the flow regimes crossing over the masts. To enhance the vibratory behavior of a typical mast, under the influence of flow induced vibrations,three different mass distributions along the length of the mast were considered. The different mass distributions were achieved by tapering the mast along its length,allocating more of the mass at its fixed end, and gradually decreasing it toward its free end. Three different tapering angles were considered for these studies. All results were compared with the results obtained for a straight circular cross-section cylindrical mast having the same overall length and mass. For a mast length of 25 meters and a total mass of 1782.74 kg, three tapered angles of 0.229, 0.458 , and 0.596 degrees, were considered. These analyses show that the first natural frequencies of the tapered masts increases from that of the straight mast. The first natural frequency of the straight mass was determined to be 0.2845 Hrz. The corresponding first natural frequencies for the masts with tapered angle of 0.229, 0.458, and 0.596 became 0.417, 0.5911, and 0.7435Hrz. respectively. In addition to the natural frequency analyses, dynamic responses analyses of these masts were determined under the influence of the harmonic excitations resulting from the vortex shedding cause by the wind flow. For the tapered angles chosen in these studies the maximum displacement of the free ends of these masts were determined. For a wind speed of 10 m/s the free-end displacements of the tapered masts were determined to be (500, 1000, 1300)* 10-6 meters for tapered angles of 0.229,0.458, 0.596 degrees respectively. The computational analyses performed in this work were accomplished by using SAP 2000 software.
Majid Rashidi, PhD (Committee Chair)
Rama Gorla, PhD (Committee Member)
Earnest Poulos, Phd (Committee Member)
MASTS; TAPERED; straight mast; TAPERED MASTS; SAP2000; STRAIGHT AND TAPERED; vortex shedding

Recommended Citations

Citations

  • Bani Hani, A. (2009). Wind Flow Induced Vibrations of Tapered Masts [Master's thesis, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243389014

    APA Style (7th edition)

  • Bani Hani, Ahmad. Wind Flow Induced Vibrations of Tapered Masts. 2009. Cleveland State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1243389014.

    MLA Style (8th edition)

  • Bani Hani, Ahmad. "Wind Flow Induced Vibrations of Tapered Masts." Master's thesis, Cleveland State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243389014

    Chicago Manual of Style (17th edition)

csu1243389014
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© 2009, all rights reserved.
This open access ETD is published by Cleveland State University and OhioLINK.