STRENGTH AND DSM DESIGN OF END-BOLTED COLD-FORMED COLUMNS FAILING IN DISTORTIONAL MODES
Warlley S. Santos1, Alexandre Landesmann1* and Dinar Camotim2
1 PEC/COPPE/UFRJ, Programa de Eng. Civil, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
2 CERIS, ICIST, DECivil, Instituto Superior Técnico, Universidade de Lisboa, Portugal
This work reports the results of an experimental investigation concerning the influence of bolted end support conditions on the failure loads of cold-formed steel lipped channel columns buckling and failing in distortional modes, as well as on their prediction by means of the Direct Strength Method (DSM). This type or end support conditions, commonly used in the civil engineering construction market, consists of pairs of high-strength cylindrical bolts with hexagonal heads and nuts, which are inserted in two standard-size holes located at the intersections of the flanges with the centroidal axis parallel to the web. After describing the test set-up and procedure, the experimental failure loads obtained are presented and discussed. These acquired failure load data are subsequently employed to assess the quality of their estimates by means of the currently codified DSM column distortional design curve. Because this assessment leads to the conclusion that the current DSM curve clearly overestimates the experimental failure loads obtained, a new/modified design curve is preliminarily proposed and shown to improve considerably the prediction quality (safety and reliability) of the end-bolted column failure loads, thus providing motivation and encouragement to continue the search for an efficient DSM-based design approach for end-bolted columns failing in distortional modes.
Cold-formed steel lipped channel columns; Bolted end support conditions; Distortional failure; Experimental investigation; Direct Strength Method (DSM) design