3.3.1 Steel Backing at Continuity Plates
Steel backing used at continuity plate-to-column welds need not be removed. At column flanges, steel backing left in place shall be attached to the column flange using a continuous 5/16 in. (8 mm) fillet weld on the edge below the CJP groove weld.
When backing is removed, the root pass shall be backgouged to sound weld metal and backwelded with a reinforcing fillet weld. The reinforcing fillet weld shall be continuous with a minimum size of 5/16 in. (8 mm).
3.3.2 Steel Backing at Beam Bottom Flange
Where steel backing is used with CJP groove welds between the bottom beam flange and the column, the backing shall be removed.
Following the removal of steel backing, the root pass shall be backgouged to sound weld metal and backwelded with a reinforcing fillet weld. The size of the reinforcing fillet weld leg adjacent to the column flange shall be a minimum of 5/16 in. (8 mm), and the reinforcing fillet weld leg adjacent to the beam flange shall be such that the fillet weld toe is located on the beam flange base metal.
Exception: If the base metal and weld root are ground smooth after removal of the backing, the reinforcing fillet weld adjacent to the beam flange need not extend to the base metal.
3.3.3 Steel Backing at Beam Top Flange
Where steel backing is used with CJP groove welds between the top beam flange and the column, and the steel backing is not removed, the steel backing shall be attached to the column by a continuous 5/16 in. (8 mm) fillet weld on the edge below the CJP groove weld.
3.3.4 Prohibited Welds at Steel Backing
Backing at beam flange-to-column flange joints shall not be welded to the underside of the beam flange, nor shall tack welds be permitted at this location. If fillet welds or tack welds are placed between the backing and the beam flange in error, they shall be repaired as follows:
- (1) The weld shall be removed such that the fillet weld or tack weld no longer attaches the backing to the beam flange.
- (2) The surface of the beam flange shall be ground flush and shall be free of defects.
- (3) Any gouges or notches shall be repaired. Repair welding shall be done with E7018 SMAW electrodes or other filler metals meeting the requirements of Section 3.1 for demand critical welds. A special welding procedure specification (WPS) is required for this repair. Following welding, the repair weld shall be ground smooth.
3.3.5 Nonfusible Backing at Beam Flange-to-Column Joints
Where nonfusible backing is used with CJP groove welds between the beam flanges and the column, the backing shall be removed and the root backgouged to sound weld metal and backwelded with a reinforcing fillet weld. The size of the reinforcing fillet weld leg adjacent to the column shall be a minimum of 5/16 in. (8 mm), and the reinforcing fillet weld leg adjacent to the beam flange shall be such that the fillet weld toe is located on the beam flange base metal.
Exception: If the base metal and weld root are ground smooth after removal of the backing, the reinforcing fillet weld adjacent to the beam flange need not extend to the base metal.