AISC LRFD 1.pdf

58 WELDS [Sect. J2.5. Combination of WeldsIf two or more of the general types of welds (groove, fillet, plug, slot) are combinedin a single joint, the design strength of each shall be separately computed with referenceto the axis of the group in order to determine the design strength of thecombination.6. Weld Metal RequirementsThe choice of electrode for use with complete-joint-penetration groove welds subjectto tension normal to the effective area shall comply with the requirements formatching weld metals given in AWS D1.1.Weld metal with a specified Charpy V-notch (CVN) toughness of 20 ft-lbs (27 J) at40°F (4°C) shall be used in the following joints:(a) Complete-joint-penetration groove welded T and corner joints with steel backingleft in place, subject to tension normal to the effective area, unless the jointsare designed as noted in Table J2.5 (see footnote d).(b) Complete-joint-penetration groove welded splices subject to tension normal tothe effective area in Group 4 and Group 5 shapes and shapes built up by weldingplates more than two in. (50 mm) thick.The manufacturer’s Certificate of Conformance shall be sufficient evidence ofcompliance.7. Mixed Weld MetalWhen notch-toughness is specified, the process consumables for all weld metal,tack welds, root pass, and subsequent passes deposited in a joint shall be compatibleto assure notch-tough composite weld metal.8. Preheat for Heavy ShapesFor ASTM A6/A6M Group 4 and 5 shapes and welded built-up members made ofplates more than two in. (50 mm) thick, a preheat equal to or greater than 350°F(175°C) shall be used when making groove-weld splices.J3. BOLTS AND THREADED PARTS1. High-Strength BoltsUse of high-strength bolts shall conform to the provisions of the Load and ResistanceFactor Design Specification for Structural Joints Using ASTM A325 or A490Bolts, as approved by the Research Council on Structural Connections, except asotherwise provided in this Specification.If required to be tightened to more than 50 percent of their specified minimum tensilestrength, A449 bolts in tension and bearing-type shear connections shall havean ASTM F436 hardened washer installed under the bolt head, and the nuts shallmeet the requirements of ASTM A563. When assembled, all joint surfaces, includingthose adjacent to the washers, shall be free of scale, except tight mill scale. AllA325 or A325M and A490 or A490M bolts shall be tightened to a bolt tension notless than that given in Table J3.1 or J3.1M, except as noted below. Tightening shallbe done by any of the following methods: turn-of-nut method, a direct tension indicator,calibrated wrench, or alternative design bolt.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION