AISC LRFD 1.pdf

Comm. J1.] GENERAL PROVISIONS 231 Preheating for thermal cutting is required to minimize the formation of a hardsurface layer. Grinding to bright metal and inspection using magnetic particle or dye-penetrantmethods is required to remove the hard surface layer and to assure smooth transitionsfree of notches or cracks.In addition to tension splices of truss chord members and tension flanges of flexuralmembers, other joints fabricated of heavy sections subject to tension should begiven special consideration during design and fabrication.8. Placement of Welds and BoltsSlight eccentricities between the gravity axis of single and double angle membersand the center of gravity of connecting rivets or bolts have long been ignored as havingnegligible effect on the static strength of such members. Tests (Gibson andWake, 1942) have shown that similar practice is warranted in the case of weldedmembers in statically loaded structures.However, the fatigue life of eccentrically loaded welded angles has been shown tobe very short (Kloppel and Seeger, 1964). Notches at the roots of fillet welds areharmful when alternating tensile stresses are normal to the axis of the weld, as couldoccur due to bending when axial cyclic loading is applied to angles with end weldsnot balanced about the neutral axis. Accordingly, balanced welds are indicatedwhen such members are subjected to cyclic loading (see Figure C-J1.3).9. Bolts in Combination with WeldsWelds will not share the load equally with mechanical fasteners in bearing-typeconnections. Before ultimate loading occurs, the fastener will slip and the weld willcarry an indeterminately larger share of the load.Accordingly, the sharing of load between welds and A307 bolts or high-strengthbolts in a bearing-type connection is not recommended. For similar reasons, A307bolts and rivets should not be assumed to share loads in a single group of fasteners.For high-strength bolts in slip-critical connections to share the load with welds it isFigure C-J1.3. Balanced welds.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION