Structural Steel and Welding
Core concepts
Steel questions test fit-up, connection type, and inspection. Know bolted vs. welded connections, high-strength bolts (snug-tight vs. pretensioned), hole types (standard, oversize, slotted), and edge distance. For welding, know the common processes (SMAW, GMAW, FCAW), joint types (butt, lap, tee, corner), weld types (fillet, groove), and the meaning of weld symbols on drawings.
Inspection matters: visual inspection of every weld, plus nondestructive testing (ultrasonic, magnetic particle, dye penetrant) where specified. Know that welders must be qualified and procedures prequalified or qualified. Also know shop primer effects, galvanizing concerns, and erection tolerances.
Traps to watch
- Assuming any weld symbol means a full-penetration weld - read the tail and size.
- Using standard holes where oversize is specified, or vice versa.
- Skipping preheat on thick or cold-weather steel.
- Treating a visual pass as a substitute for required NDT.
- Ignoring coating compatibility between shop primer and field paint.
Rule of thumb
Read a weld symbol left to right: reference line, arrow side vs. other side, size, length, pitch, tail. If the size is on the left of the symbol, it applies to the arrow side.
Worked example
A drawing shows a fillet weld symbol with "1/4" on the arrow side and a length of 6 with a pitch of 12. That means 1/4-inch fillet, 6 inches long, spaced every 12 inches on the arrow side. Confirm before fabrication - misreading pitch as continuous length is a common and costly error.