AISC LRFD 1.pdf

273Comm. A-KAPPENDIX JCONNECTIONS, JOINTS, AND FASTENERSJ2. WELDS4. Design StrengthWhen weld groups are loaded in shear by an external load that does not act throughthe center of gravity of the group, the load is eccentric and will tend to cause a relativerotation and translation between the parts connected by the weld. The pointabout which rotation tends to take place is called the instantaneous center of rotation.Its location is dependent upon the load eccentricity, geometry of the weldgroup, and deformation of the weld at different angles of the resultant elementalforce relative to the weld axis.The individual resistance force of each unit weld element can be assumed to act on aline perpendicular to a ray passing through the instantaneous center and that element’slocation (see Figure C-A-J2.1).The ultimate shear strength of weld groups can be obtained from the load deformationrelationship of a single-unit weld element. This relationship was originallygiven by Butler et al. (1972) for E60 (E43) electrodes. Curves for E70 (E48) electrodesused in the Appendix were obtained by Lesik and Kennedy (1990).Unlike the load-deformation relationship for bolts, strength and deformation performancein welds are dependent on the angle that the resultant elemental forcemakes with the axis of the weld element (see Figure C-A-J2.1). The actual loaddeformation relationship for welds is given in Figure C-A-J2.2, taken from LesikFig. C-A-J2.1. Weld element nomenclature.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION