Seminar - Siva Sivakumaran - Recent Research Studies on Steel Structures at McMaster University, Canada
Wednesday, May 11, 2005, 1.10 - 1.50 pm
Civil Engineering Lecture Room 3
The presenter K.S.Sivakumaran is a professor attached to the Department of Civil Engineering, McMaster University, Hamilton, Ontario, Canada. He is currently a visiting professor at The University of Sydney. This presentation describes three ongoing research projects related to steel structures.
 Effective Reinforcement Schemes For Cold-Formed Steel Joists With Web Openings
The floor joists of Cold-Formed Steel (CFS) structures often require large web openings. Reinforcement of such openings may mitigate the detrimental effects of such web openings. This presentation is based on an experimental investigation which considered galvanized lipped channel sections having circular, square, and rectangular openings, and two associated reinforcement schemes. The focus of this part of the investigation was on flexural strength of such joists. Two lipped channel sections were set face-to-face to form the test specimen assembly. Based on eleven sets of three identical flexural tests, it was determined that [a] the tension zones of the web having a large opening need not be reinforced, [b] closely spaced screw fastening of reinforcements (bridging channel) is essential, and [c] the reinforcements need to be fastened as close as possible to the compression edges of the opening, in order to minimize crippling of these edges. This presentation demonstrates that it is possible to establish cost effective reinforcement schemes for CFS sections having large web openings.
 Behaviour Of Plasma Cut-Welded H-Shaped Steel Columns
H-shaped steel column members may be fabricated by welding together pre-cut flanges and the web. More and more fabricators are using plasma-cutting technique instead of traditional flame cutting. Different fabrication techniques result in different degrees of geometric imperfections and residual stresses, which can have considerable effects on the strength of steel columns. Recently an experimental investigation was conducted to establish the imperfections characteristics and the strength of plasma cut-welded H-shaped steel columns and similar flame cut-welded H-shaped steel columns. The geometric imperfection measurements were taken at closely spaced grid locations immediately after cutting, immediately after welding, and immediately after separation of the long columns into test columns. Geometric imperfections associated with plasma cut element and members were found to be less than that of the corresponding elements and members made by flame cutting. Method of Section technique was used to establish the built-up residual stresses in the plate, plate strip, and in the welded columns. Higher residual stress values were observed in flame cut welded columns. The column strengths were compared with current code predictions.
 Effects Of Flange Fastener Holes On The Flexural Strength Of Steel Beams.
Structural steel with specified minimum yield strength of 350MPa is currently the norm in Canada. Lately the steel grade ASTM A992/A992M has become the dominant material specification for wide flange shapes in USA. Over the years the yield-to-tensile strength ratio of structural steel has increased from 0.5 to currently a code permitted maximum of 0.85. It is often necessary to have bolt holes in flanges of the steel beams, particularly for connection purposes. Comparison of corresponding design provisions of international steel standards indicates that the current 15% exemption specified in the Canadian Steel design code may be restrictive for mild-carbon, and A36 steel grades, whereas it may unconservative for newer grade steels such as 350W and A992/A992M grade steel. The overall objective of this research is to quantify the effects of flange fastener holes on the flexural strength of steel beams, particularly made of A992/A992M steel.