AISC LRFD 1.pdf

Comm. M4.] ERECTION 261It is suggested that snug-tight bearing-type connections be used in applicationswhere A307 bolts would be permitted.This section provides rules for the use of oversized and slotted holes paralleling theprovisions which have been in the RCSC Specification (RCSC, 1994) since 1972,extended to include A307 bolts which are outside the scope of the high-strengthbolt specifications.M3. SHOP PAINTINGThe surface condition of steel framing disclosed by the demolition of long-standingbuildings has been found to be unchanged from the time of its erection, except atisolated spots where leakage may have occurred. Even in the presence of leakage,the shop coat is of minor influence (Bigos, Smith, Ball, and Foehl, 1954).The LRFD Specification does not define the type of paint to be used when a shopcoat is required. Conditions of exposure and individual preference with regard tofinish paint are factors which bear on the selection of the proper primer. Hence, asingle formulation would not suffice. For a comprehensive treatment of the subject,see SSPC (1989).5. Surfaces Adjacent to Field WeldsThe Specification allows for welding through surface materials, including appropriateshop coatings, that do not adversely affect weld quality nor create objectionablefumes.M4. ERECTION2. BracingFor information on the design of temporary lateral support systems and componentsfor low-rise building, see Fisher and West (1997).4. Fit of Column Compression Joints and Base PlatesTests at the University of California-Berkeley (Popov and Stephen, 1977) on splicedfull-size columns with joints that had been intentionally milled out-of-square, relativeto either strong or weak axis, demonstrated that the load-carrying capacity wasthe same as that for a similar unspliced column. In the tests, gaps of 1 16-in. (2 mm)were not shimmed; gaps of 1 4-in. (6 mm) were shimmed with non-tapered mild steelshims. Minimum size partial-joint-penetration welds were used in all tests. No testswere performed on specimens with gaps greater than 1 4-in. (6 mm).5. Field WeldingThe purpose of wire brushing shop paint on surfaces adjacent to joints to be fieldwelded is to reduce the possibility of porosity and cracking and also to reduce anyenvironmental hazard. Although there are limited tests which indicate that paintedsurfaces result in sound welds without wire brushing, other studies have resulted inexcessive porosity and/or cracking when welding coated surfaces. Wire brushing toreduce the paint film thickness minimizes rejectable welds. Grinding or other proceduresbeyond wire brushing is not necessary.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION