<p>Welded built-up structural steel members are widely used as columns, beams, and
beam-columns in various buildings, bridges, industrial complexes, etc. Modern cutting
techniques are used in the fabrication of such members. Besides traditional saw cutting and
oxy-flame cutting, the modern cutting techniques include plasma cutting, laser cutting, water- jet
cutting, etc. The different cutting techniques induce different degrees of Heat Affected
Zones (HAZ), which subsequently creates different degrees of geometrical and mechanical
imperfections (residual stresses). Therefore, it could be expected that the true behavior of
structural steel columns manufactured by such cutting techniques be different.</p><p>The main objective of this investigation was to study the characteristics and behavior of
plasma cut-welded H-shaped steel columns at different slenderness ratios. However, this
investigation also considered similar flame cut-welded H-shaped steel columns for comparison
purposes. The H-shaped column sections were fabricated from plates having specified yield
strength of 350MPa. First, the initial plate was cut into plate strips and then the plate strips
(flanges and web) were welded together to form the H-shaped section in this investigation. The
strength of these columns were established under uni-axial compressive loading with pinned
end condition, allowing for minor axis rotation. Moreover, the structural imperfections such as
residual stresses and geometrical imperfections were established. The residual stresses
distributions were established at various stages of fabrication processes using the "method of
section" technique. That is, the residual stresses in initial plate, plate strips (cutting effects), and
column sections (cutting and welding effects) were established. Similarly, the geometrical
imperfections were established at various stages of fabrication processes in this investigation.The temperature profiles were measured during the cutting and welding processes. As part of
the scientific documentation, the mechanical characteristic of virgin steel plates were obtained
by standard coupon tensile test.</p><p>Based on the experimental results on column strength, the general behavior of plasma
cut columns and flame cut columns were similar. However, it was found that the plasma cut-welded
steel columns seemed to carry higher loads than that of flame cut-welded columns for
higher slenderness ratios( λ≥1). For lower slenderness ratios (0.5<λ<1), it was found that the
flame cut-welded columns had higher strength than plasma cut-welded columns in this
investigation. The residual stress distribution of both plasma cut column section and flame cut
column section had the same general distribution. However, in general, the flame cut columns
had high intensity of tensile residual stresses at their flange tips than the plasma cut columns.
Moreover, the out-of-plane imperfections of column sections were within the code limitations.
However, it was found that the flame cut-welded H-shaped steel columns seemed to have
higher out-of-plane imperfections than the similar plasma cut-welded H-shaped steel columns
in this investigation.</p> / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21840 |
| Date | 02 1900 |
| Creators | Arasaratnam, Pramalathan |
| Contributors | Sivakumaran, K. S., Civil Engineering |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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