High Strength Connectors
Provided there is contact on the area of the annular ring around the bolt, this is not cause for concern. Be sure to follow correct bolt installation procedures as given in RCSC specification, i.e. start at stiffest portion of the connection working toward free edge(s). See RCSC 2009 Specification p.30-33 for more on relevant contact area of pre-tensioned bolts. It is important to note that the slip resistance of any “slip-critical” connection is based on the total clamping normal force and that the individual tensions of pre-tensioned bolts will all vary somewhat. This is not a cause of concern for HSCs, as the HSC will never see a compressive load in excess of the tensile load, so a one-time slip into bearing under full tension could occur. However, as that force is the RyFyAg, it will only happen in a design level seismic event.
To ensure that the centre-to-centre of the bolt hole patterns on either end of the brace is correct, we often recommend:
- Drill holes in the HSCs for one end only then weld both HSCs to the tube followed by accurate layout of the hole in the HSC at the opposite end based on the actual position of the holes in the first end. Then drill the holes in the remaining HSC. This will negate any concern over weld shrinkage.
- Consider using oversize holes in the gusset (only). This is allowed by code - an exception allows the use of oversized holes in one ply of connections of diagonal bracing members in Sections F1, F2, F3 and F4 in AISC 341-10 when the connection is designed as a slip-critical joint.
- Make sure the erector surveys any critical items, such as anchor rods, before delivering the steel.
Whether your interest in cast steel components is general or project-specific, we look forward to speaking with you.