Issues of alternating load in design of cold-formed steel frames with lap joints

The paper raises the issues of alternating loads in designing of cold-formed steel frames with blind bolt lap joints. Based on own research and information found in the literature pointed out the need to develop the procedures for calculating such connections, taking into account their actual behaviour, i.e. according to proper hysteresis loops. Presented also the method of determining of nonlinear force-displacement (F-d) and moment-rotation (M-f) characteristics describing the behaviour of a single-cut connections of cold-formed sections with blind fasteners of the type BOM [1], loaded in one direction. The proposed formulas are based on previously unpublished research results and allow for determination of mentioned dependencies on the basis of selected physical parameters of such connections. The curves of the relationships F-d and M-f obtained from the proposed formulas were compared in graphs with experimental curves obtained during the tests of elements in which connections has been loaded in both one direction and alternately. As a conclusion, the predicted directions for further research are presented.

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