Inelastic behaviour of cold-formed channel sections in bending
thesisposted on 02.02.2017 by Maduliat, Soheila
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This thesis investigates the behaviour of cold-formed channel sections with edge stiffener under pure bending. The primary aim of this research is to examine the inelastic bending capacity of cold-formed channel sections and in doing so provide design rules to account for such behaviour. Design rules are prepared for cold-formed steel specifications (inelastic reserve capacity) NASPEC (2007) and AS/NZS4600 (2005) as well as hot-rolled steel specifications (compact, non-compact and slender classes) AS4100 (1998). To investigate the behaviour of cold-formed channel sections under pure bending, this study conducts an extensive experimental and numerical analysis of 42 cold-formed channel sections in three different geometrical categories (simple channel sections, channel sections with simple edge stiffener and channel sections with complex edge stiffener) to determine the effect of different edge stiffeners on the ultimate strength of cold-formed channel sections. The sections are made from cold-formed G450 steel with nominal thickness of 1.6mm and varying theoretical buckling stresses ranging between elastic to seven times the yield stress. The ultimate bending moment capacities of the sections are calculated from six methods being the: test result ( ), NASPEC (2007) design rules ( ), AS/NZS4600 (2005) design rules ( ), DSM ( ), EUROCODE3 (2006) design rules ( ) and AS4100 (1998) design rules ( ). The is then used as a benchmark to gauge the accuracy of the , , , and . The results of the test investigations showed that the existing design rules in NASPEC (2007), AS/NZS4600 (2005), DSM and EUROCODE3 (2006) are conservative and the sections classifications in AS4100 (1998) are inaccurate for cold-formed channel sections. Therefore, the experimental results were used to revise the existing design methods (NASPEC (2007), AS/NZS4600 (2005) and DSM) for determining the ultimate capacity of cold-formed channel sections in bending and also defining new slenderness limits for sections classifications in AS4100 (1998). The yield line mechanism model is proposed and compared with the test results in order to investigate the behaviour of cold-formed channels with edge stiffener after collapse. Numerical (finite element) analyses is then developed and verified with the test results and used to investigate deformation process of cold-formed channel sections under bending that could not be monitored during the experimental program to complement the test results. The outcome of this study is to determine the section geometry for which a cold-formed channel section can reach the fully plastic capacity and maintain it for sufficient rotation, such that when employed in a structure such as a portal frame it may be considered applicable for plastic mechanism analysis, thus allowing for increased design capacities and more economical structural solutions.