Experimental investigation on bolted moment connections among cold formed steel members

The paper presents an experimental investigation on the structural performance of cold formed steel members with bolted moment connections. Two lipped C sections back-to-back with interconnections are used as beam and column members. A number of connection configurations with gusset plates of both hot rolled steel and cold formed steel are proposed to form bolted moment connections to accommodate members in practical orientations. Only the webs of lipped C sections are connected with bolts; the section flanges are not connected for ease of construction. The structural performance of all the tests are presented in detail. Four modes of failure were identified among the tests: BFcsw-bearing failure in section web around bolt hole LTBgp-lateral torsional budding of gusset plate FFcs-flexural failure of connected member, and CBcol-combined compression and bending failure of column member. It is shown that bearing failure is a ductile mode with large deformation capacity, and other failure modes may creep in to cause sudden collapse. While lateral torsional buckling of gusset plates causes pre-mature failure of the connections at low applied load, flexural failure is more desirable as over 80% of the moment capacity of the connected members may be safely mobilised at the connections. In the absence of effective torsional restraint at the column ends, the column members may fail in combined compression and bending. Among sixteen component and system tests, the moment resistance of bolted moment connections with four bolts per member was found to lie between 42% and 84% of the moment capacities of the connected members. Thus, it was demonstrated that moment connections among cold formed steel members are structurally feasible and economical through rational design. (C) 1999 Elsevier Science Ltd. All rights reserved.