Warping and Distortion at I-Section Joints

The warping and distortion at the ends of members of doubly symmetric I-sections are studied theoretically and experimentally, and the increases in the resistances to warping and distortion caused by web stiffeners or by additional webs are investigated. Analytical expressions are given for the warping and distortion restraint stiffnesses of single members. The behavior of rigid angle joints between I-section members is then studied, and it is deduced that the warping and distortion at a joint are interdependent. A finite element model is proposed, and this is used to determine the effects of member length, joint angle, and stiffener arrangement on the restraint against end warping. Simple approximations are obtained for estimating the warping restraints, and these are shown to be conservative.