| doi:10.3850/978-981-08-6218-3_SS-Th019 |
 Final Paper PDF
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SHEAR TESTS OF LITESTEEL BEAMS WITH WEB OPENINGS
P. Keerthana and M. Mahendranb
Faculty of Built Environment and Engineering, Queensland University of Technology,
Brisbane, Queensland.
ap.keerthan@qut.edu.au
bm.mahendran@qut.edu.au
EXTENDED ABSTRACT
LiteSteel Beam (LSB) is a new cold-formed steel hollow flange channel beam produced by OneSteel Australian Tube Mills. The LSB has a unique shape including two rectangular hollow flanges, and is manufactured using dual electric resistance welding and automated continuous roll-forming technologies. It has the beneficial characteristics of including torsionally rigid closed rectangular flanges combined with economical fabrication processes from a single strip of high strength steel. The cross-sectional shape of the beam has been designed such that it provides a high structural performance compared to other cold-formed steel beams produced to date. These integral benefits of lightweight, strength, and ease of constructability offer a new option of using LSBs for structural engineers.
The LSB sections are commonly used as flexural members in residential, industrial and commercial buildings. In order to ensure safe and efficient designs of LSBs, many research studies have been undertaken on the flexural behaviour of LSBs. Current practice in flooring systems is to include openings in the web element of floor joists or bearers so that building services can be located within them. Shear behaviour of LSBs with web openings is more complicated while their shear strengths are considerably reduced by the presence of web openings. However, no research has been undertaken on the shear behaviour and strength of LSBs with web openings. Therefore a detailed experimental study involving 26 shear tests was undertaken to investigate the shear behaviour and strength of different LSB sections with web openings. The main aim of this research is to investigate the effect of circular web openings of varying diameters on the shear capacities of different LSB sections. Simply supported test specimens of LSBs with an aspect ratio of 1.5 were loaded at midspan until failure. A 30 mm gap was included between the two LSB sections to allow the test beams to behave independently while remaining together to resist torsional effects. Three opening sizes of 60, 102 and 127 mm were chosen based on the standard sizes used by the LSB manufacturers.
A significant effect of web openings is web crippling under loading. This research is not concerned with web crippling and therefore experiments were conducted in such a manner to prevent web crippling. In order to fully understand the shear behaviour of LSB sections with web openings several important issues were considered when deciding parameters such as the depth of web openings to clear height of web (dwh/d1) and the clear height of web to thickness of web (d1/tw). Test specimens of LSBs were designed to fail in shear prior to reaching other section capacities. This paper presents the details of the shear tests of LSBs with circular web openings, and the results.
Experimental shear capacities were compared with the predicted capacities using the available design rules, including the current design rules in AS/NZS 4600. These design rules are based on a reduction factor (qs) applied to the shear capacity of beams without web openings. The reduction factor is expressed as a function of the ratio of depth of web openings to clear height of web (dwh/d1). Comparison of shear capacity results showed that the current design rules in cold-formed steel structures design codes (AS/NZS 4600) are very conservative for the shear design of LSBs with web openings. It was found that Shan et al.’s design equations are conservative for the shear design of LSBs with web openings while McMahon et al.’s design equations are unconservative. Appropriate improvements have been proposed in the form of modified shear capacity reduction factors to determine the shear capacity of LSBs with web openings based on the experimental results from this study.