Web crippling behaviour of cold-formed steel sections with circular web openings under one-flange loading

  • Ying Lian

    Student thesis: Doctoral ThesisDoctor of Philosophy

    Abstract

    Web openings are increasingly used in load bearing cold-formed steel members, such as wall studs or floor joints, to facilitate services in buildings. In such members, web crippling can occur at points of concentrated loads, which will be influenced by the size and position of the openings. Due to the improvement of cold-formed techniques, the material thickness and strength of channel section is increased but research on the cold-formed steel members with web openings is limited. Therefore, the behaviour and design of cold-formed steel channel members with web openings are investigated in this study.
    Both experimental tests and non-linear elasto-plastic finite element analysis (FEA) are used to investigate the effect of circular web openings on web crippling behaviour of cold-formed steel channel-sections with circular web openings under interior-one-flange (IOF) and end-one-flange (EOF) loading condition; the cases of both flanges unfastened and flanges fastened are considered. In the case of the tests with web openings, the holes are located either centred above the bearing plates or with a horizontal clear distance to the near edge of the bearing plate.
    Good agreement between the experimental tests and non-linear finite element models was obtained. The finite element models were then used in a parametric study to investigate the effect of cross-section sizes and web holes on the web crippling strengths of channel sections.
    The web crippling strengths of cold-formed steel channel sections without holes from experimental and numerical investigations were compared with the current design strengths from British Standard, Eurocode and North American Specification (NAS). Only the NAS provides design strengths for the case of circular holes with a horizontal clear distance to the near edge of bearing plates and only for the case of flanges fastened to the bearing plates. However, NAS design code has limitations and also failed to predict the web crippling strengths of cold-formed channel-sections with holes. Therefore, new design strength reduction factor equations for cold-formed steel channel-sections need to be proposed.
    An extensive statistical analysis of web crippling for cold-formed steel channel-sections with web holes was carried out, including 135 test results and 1463 numerical results. In addition, design recommendations in the form of web crippling strength reduction factors were proposed. Reliability analysis was performed to evaluate the reliability of the proposed strength reduction factors. It was shown that the proposed strength reduction factors agree well with the experimental and finite element results.
    Date of Award2016
    Original languageEnglish
    Awarding Institution
    • Queen's University Belfast
    SupervisorJames Lim (Supervisor)

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