K-joints of double-chord square hollow sections

Abstract

A new concept utilizing double-chord square hollow sections in welded K-joints of Warren trusses is described. The experimental results of 29 tests are reported, including four connection types: standard, channel, bolted, and back-to-back. The latter type comprised gapped, overlapped, and gapped with connecting stiffener plates.The results indicate that the standard type is an excellent joint in both strength and stiffness. The channel type is generally susceptible to twisting. It was found adequate only when a significant increase in chord thickness[Formula: see text] was employed. The bolted connection appears to hold promise when on-site assembly of large trusses is necessary. Its performance was further improved by connecting the chords with small tie bars. The back-to-back type needed to be reinforced or fully overlapped to develop full branch member strength. The double-chord system of connection reveals itself to be much superior in strength to an equivalent single-chord joint.The effects of eccentricity, branch member chord angle, and chord preloading were investigated. Interaction formulae are presented for the standard- and channel-type joints and their use is illustrated with examples. Satisfactory agreement between predicted and experimental ultimate strengths was obtained for joints that suffered from a chord failure at the connection.