AISC LRFD 1.pdf

170 MATERIAL [Comm. A3.is intended for pipe flange bolting and Gr. A is the grade long in use for structuralapplications.4. Anchor Rods and Threaded RodsSince there is a limit on the maximum available length of A325 or A325M andA490 or A490M bolts, the attempted use of these bolts for anchor rods with designlengths longer than the maximum available lengths has presented problems in thepast. The inclusion of A449 and A354 materials in this Specification allows the useof higher strength material for bolts longer than A325 or A325M and A490 orA490M bolts. The designer should be aware that pretensioning of anchor rods is notrecommended due to relaxation and the potential for stress corrosion afterpretensioning.The designer should specify the appropriate thread and SAE fit for threaded rodsused as load-carrying members.5. Filler Metal and Flux for WeldingThe filler metal specifications issued by the American Welding Society (AWS) aregeneral specifications which include filler metals suitable for building construction,as well as consumables that would not be suitable for building construction.For example, some electrodes covered by the specifications are specifically limitedto single pass applications, while others are restricted to sheet metal applications.Many of the filler metals listed are “low hydrogen,” that is, they deposit filler metalwith low levels of diffusible hydrogen. Other materials are not. Filler metals listedunder the various AWS A5 specifications may or may not have required impacttoughness, depending on the specific electrode classification. Section J2.6 hasidentified certain welded joints where notch toughness of filler metal is needed inbuilding construction. However, on structures subject to dynamic loading, fillermetals may be required to deliver notch-tough weld deposits in other joints. Fillermetals may be classified in either the as-welded or post weld heat-treated(stress-relieved) condition. Since most structural applications will not involvestress relief, it is important to utilize filler materials that are classified in conditionssimilar to those experienced by the actual structure.When specifying filler metal and/or flux by AWS designation, the applicable standardspecifications should be carefully reviewed to assure a complete understandingof the designation reference. This is necessary because the AWS designationsystems are not consistent. For example, in the case of electrodes for shielded metalarc welding (AWS A5.1), the first two or three digits indicate the nominal tensilestrength classification, in ksi, of the filler metal and the final two digits indicate thetype of coating. For metric designations, the first two digits times 10 indicate thenominal tensile strength classification in MPa. In the case of mild steel electrodesfor submerged arc welding (AWS A5.17), the first one or two digits times 10 indicatethe nominal tensile strength classification for both U.S. Customary and metricunits, while the final digit or digits times 10 indicate the testing temperature indegrees F (degrees Celsius), for filler metal impact tests. In the case of low-alloysteel covered arc welding electrodes (AWS A5.5), certain portions of the designationindicate a requirement for stress relief, while others indicate no stress reliefrequirement.Engineers do not, in general, specify the exact filler metal to be employed on a par-LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION