AISC LRFD 1.pdf

234 WELDS [Comm. J2.joint, the resulting rotation of the joint when pulled will not be excessive, as shownin Figure C-J2.3. Fillet welded lap joints under tension tend to open and apply atearing action at the root of the weld as shown in Figure C-J2.4b, unless restrainedby a force F as shown in Figure C-J2.4a.End returns are not essential for developing the capacity of fillet welded connectionsand have a negligible effect on their strength. Their use has been encouragedto insure that the weld size is maintained over the length of the weld, to enhance thefatigue resistance of cyclically loaded flexible end connections, and to increase theplastic deformation capability of such connections.The weld capacity database on which the specifications were developed had no endreturns. This includes the study by Higgins and Preece (1968), seat angle tests byLyse and Schreiner (1935), the seat and top angle tests by Lyse and Gibson (1937),beam webs welded directly to column or girder by fillet welds by Johnston andDeits (1942), and the eccentrically loaded welded connections reported by Butler,Pal, and Kulak (1972). Hence, the current design-resistance values andjoint-capacity models do not require end returns when the required weld size isprovided. Johnston and Green (1940) noted that movement consistent with thedesign assumption of no end restraint (i.e., joint flexibility) was enhanced withoutend returns. They also verified that greater plastic deformation of the connectionwas achieved when end returns existed, although the strength was not significantlydifferent.Fig.C-J2.2. Longitudinal fillet welds.Fig. C-J2.3. Minimum lap.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION