Title page for ETD etd-05172010-225040


Type of Document Master's Thesis
Author Soroori Rad, Behrooz H.
Author's Email Address behroozs@vt.edu
URN etd-05172010-225040
Title Experiments on Cold-Formed Steel Beams with Holes
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Moen, Cristopher D. Committee Chair
Cousins, Thomas E. Committee Member
Roberts-Wollmann, Carin L. Committee Member
Keywords
  • Cold-Formed Steel Beams
  • Holes
  • Elastic Buckling
  • Finite Element Analysis
  • Direct Strength Method
Date of Defense 2010-05-03
Availability restricted
Abstract
Experimental testing and elastic buckling studies were performed on 68 C-section cold-formed steel joists with unstiffened rectangular web holes. Four Steel Stud Manufacturers Association (SSMA) cross-section types; 800S200-33, 800S200-43, 1000S162-54, and 1200S162-97, were evaluated to explore the influence of holes on local, distortional, and global bucking failure modes. Hole depth was varied in the tests to identify trends in ultimate strength. Ultimate strength was observed to decrease with increasing hole depth for 800S200-33, 1200S162-97 cross-sections. Due to small number of specimen and unidentified behavior of the beams, a more in depth study of the behavior of 800S200-43 and 1000S162-54 beams are necessary. Local buckling of the unstiffened strip above the hole was observed to accompany distortional buckling at the hole for the locally slender 800S200-33 and 1000S162-54 cross-sections. Thin shell finite element eigen-buckling analysis of each joist specimen, including measured cross-section dimensions and tested boundary and loading conditions, were conducted in parallel with the experiments to identify those elastic buckling mode shapes which influence load-deformation response. The distortional and lateral-torsional buckling moments were observed to decrease with increasing hole depth while a contrasting behavior was captured for local buckling modes. A modification to the AISI Direct Strength Method equations for beams with slotted web-holes was compared against the experimental results with predictions lower than tested strength. Initial cross-section imperfections led to inclined webs which decreased the capacity of the beams. The use of a water-jet cutting process was employed successfully to produce accurate holes sizes and locations in each joist specimen and is recommended for researchers and manufacturers as a method for custom fabrication of cold-formed steel members.
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