Experimental tests on built-up cold-formed steel section laced compression members

Abstract

This paper presents the detailed results of the first experimental tests investigating the behaviour and strength of axially loaded built-up cold-formed steel laced compression members, wholly assembled using Gas-Shielded Metal Arc Welding. The built-up laced test specimens consisted of two longitudinal cold-formed carbon steel channels (chords) placed back-to-back with an internal gap and connected using end batten plates and two parallel planes of single lacing systems. The compression tests were performed using built-up laced members with similar lengths but with various back-to-back gap distance. The compressive strengths, modes of failure and deformed shapes at failure were observed in the tests and reported in this paper. In addition, the load-axial shortening, load-lateral displacement, and load-axial strain relationships were also measured and reported. Overall, the new tests on built-up laced members compensated the lack of data on this form of construction and provided valuable experimental information in terms of buckling behaviour and compressive strength which may be powerfully used to develop nonlinear 3-D finite element models. The compressive strengths measured experimentally were compared against the design strengths determined using the North American Specification, Australian/New Zealand Standard and European Code for the design of cold-formed steel structures. Generally, it is shown that the specifications were accurate for the built-up cold-formed steel section laced compression members except for those failing mainly by overall buckling, where the specifications were considerably conservative.