Publication: Numerical Study on Effect of Perforation on the Structural Behaviour of Cold-formed Steel Hat-Section
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Date
2019-07
Authors
Ling, Jin Ying
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Abstract
Many structural members, for example, cold-formed steel members, hot rolled steel members, and composite beams, are often provided with perforation of various shapes and sizes, which allow flexible installation of ductwork, piping and other systems. Substantial research has been performed on Channel and Zee cold formed steel sections, but the reports on Hat section steel purlins turned out to be few only, especially Hat-section purlin with perforation. Hence, numerical study on cold-formed Hat section steel purlin with perforation was carried out to investigate the effect of perforation to structural behaviour of such sections. Finite element method using LUSAS software was chosen to carry out the research study. Five different perforation shapes were selected, which were circle, diamond, C-hexagon, square, and elongated circle. Opening depth was fixed at 0.5D2, where D2 is the inclined web depth of the section. Nonlinear bending analysis, Eigenvalue buckling analysis and linear torsion analysis were carried out. The results showed that perforated sections had lower yield moment (a percentage difference of not more than 4%), lower buckling moment (a percentage difference of not more than 24%) and higher angle of rotation (a percentage difference of not more than 6%) when compared to the section without perforation. Most of the perforated sections had similar bending characteristic despite of the difference in perforation shapes (yield moment difference less than 2%). Different perforation area affected the buckling behaviour of the Hat-section, but not the bending and torsional behaviour. The difference between bending behaviour of each section with irregular perforation shapes was insignificant and it was observed that all the nonlinear curves were similar to each other. Section with irregular perforation shapes had lower angle of rotation (2.483%) than section with elongated circle perforations. Critical opening length played a crucial role in affecting the structural behaviour of Hat-section. Furthermore, the location of perforation also influenced the structural behaviour of perforated section. When located at mid-span, yield moment was lower (6.635% for CIR-V3, 9.953% for SQU-V3, and 14.929% for ELO-V3 when compared to section without perforation), buckling moment decreased (22.749% for ELO-V3 when compared to section without perforation) and angle of rotation reduced (0.267% for DIA-V3 when compared to the section without perforation). Regardless of perforation spacing, the perforated sections with equal number of perforations behaved similar elastic characteristic before yielding. On the other hand, buckling moment and angle of rotation increased when the perforation spacing increased. Number of perforations also affected the torsional behaviour of the section with perforations. Section with diamond perforation had better structural behaviour than other perforated section whereas section with elongated circle perforation was the worst. This study provides a guideline for the design of cold-formed steel Hat-purlin
with different type of perforations, perforation location and perforation spacing. The presence of perforations gives minor effect on the structural behaviour of cold
formed steel Hat-purlin.