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The Effect of Geometric Imperfections on the Flexural Buckling of Tapered Spirally Welded Steel Tubes


123 Snell Library

August 5, 2019 10:00 am to 12:00 pm
August 5, 2019 10:00 am to 12:00 pm

Join the Department of Civil and Environmental Engineering for a PhD Defense from Fariborz Mirzaie, titled The Effect of Geometric Imperfections on the Flexural Buckling of Tapered Spirally Welded Steel Tubes. Light refreshments will be served prior to the event.

Abstract: Taking more advantage of wind and other sources of renewable clean energy is essential for a sustainable future. To this end, the cost of wind generated electricity needs to be significantly reduced. One possible solution is to build taller turbine towers taking advantage of less turbulent and higher velocity wind at higher elevations, which in turn results in producing more power per turbine and reducing the wind energy production costs. However, taller towers require larger base diameters to be able to carry the flexural loads from the turbine. Right now, transportation limitations restrict tower base diameters to 4.3 m in the US, therefore any tower taller than 80 m cannot be optimally designed. To overcome this challenge, spiral welding procedure used in the pipeline industry is being adapted to manufacture tapered tower sections on site. This new procedure reduces the fabrication costs, and enables on-site manufacturing of the tapered tubes, which in turn enables more optimally designed taller and more slender towers by eliminating transportation limitations. Spiral welding causes unique welding pattern which influences the pattern and magnitude of geometric imperfections. Since the buckling behavior of slender tubes is known to be highly imperfection sensitive, the impact of imperfections associated with the spiral welding procedure on the ultimate flexural strength of the manufactured tubes need to be thoroughly investigated. Geometric imperfections in slender tubes can arise for a variety of reasons, and for practical purposes can essentially considered to be random. Thus, statistical characterization of the manufacturing-induced imperfections is necessary to better understand the uncertainties in the buckling capacity of slender tubes.

The research completed in this dissertation proposes a simplified approach for predicting buckling strength of slender tubes by using high-resolution geometric imperfection measurements, characterizes randomness in the weld-induced geometric imperfections of spirally welded tubes, and provides a probabilistic scheme for generation of random realistic geometric imperfections which facilitates reliability-based design approaches for spirally welded tubes.

 Biography: Fariborz Mirzaie is a PhD candidate in the Department of Civil and Environmental Engineering at Northeastern University under the advisement of Associate Prof. Andrew Myers. His research interests focus on reliability-based design of spirally welded wind turbine towers. His work has been published in peer reviewed journals and presented in various conferences. He received his B.S. and M.S. degrees in Civil Engineering and Structural Engineering from Sharif University of Technology, Tehran, Iran.