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Hong KongStructural steel connections
Steel connections are bolted or welded. Bolted connections may be snug-tight, pretensioned or slip-critical. Welds are inspected visually and by non-destructive methods depending on the connection.
How the pieces are joined, and the inspection that confirms they were joined properly.
Bolted connections
Three installation conditions, in increasing order of rigor.
- Snug-tight - plies in firm contact, the most common condition
- Pretensioned - bolts tensioned to a specified minimum
- Slip-critical - pretensioned, with faying surfaces prepared so the connection resists slip
The specification tells you which is required. Installing snug-tight where slip-critical was specified is a defect that inspection is meant to catch.
Welded connections
Fillet welds and groove welds are the two broad families. Fillet welds join surfaces meeting at an angle; groove welds fill a prepared gap between members.
Welding requires qualified procedures and qualified welders. Both are documented, and both are checkable.
Visual inspection covers everything. Ultrasonic and radiographic testing are reserved for connections where failure would be serious, because they cost more. A question about which method applies is really about how critical the joint is.
Erection sequence
A steel frame becomes stable as connections are completed, and until then it depends on temporary bracing and on the sequence being followed.
Subpart R requires a minimum number of bolts in place before a load is released from a crane, and the point is that a member hanging on two bolts is not connected.
Where the answers live
Connection detail in the steel reference. Erection safety in the OSHA standards. Two books for one category, which is why knowing the split matters.
Common questions
What are the bolted connection conditions?
Snug-tight, pretensioned and slip-critical, in increasing order of rigor.
What are the two weld families?
Fillet welds joining surfaces at an angle, and groove welds filling a prepared gap.
How are welds inspected?
Visually for everything, with ultrasonic or radiographic testing where failure would be serious.
Why does erection sequence matter?
A steel frame is only stable as connections are completed, and until then it depends on bracing and sequence.
Which book covers this?
The steel reference for connection detail and the OSHA standards for erection safety.