Experimental verification of buckling-mode interaction in intermediate-length composite columns

Column buckling is a major design concern for pultruded composite columns. Interaction between the local (flange) and global (Euler) buckling modes oc curs in intermediate length thin-walled columns with near coincident buckli ng loads. The interaction of more than one buckling mode induce an unstable tertiary post-buckling path, causing imperfection sensitivity and prematur e failure. In this work, the existence of buckling-mode interaction is expe rimentally verified for intermediate length pultruded wide-flange columns s ubjected to uniaxial compression. Characterization of the interaction mode is done using both conventional testing techniques and the shadow moire opt ical technique, allowing for non-contact, full field measurement of the buc kling modes. (C) 2000 Elsevier Science Ltd. All rights reserved.