Structural collapse remains one of the deadly dozen hazards our members encounter during the steel erection process throughout the United States and Canada and is especially true when it comes to making beam to columns connections designed with double connections over column webs. The Iron Workers International Association’s (IW) 2018 ZERO Incident campaign commissioned by General President Eric Dean includes the recognition and avoidance of structural collapse incidents.
From an engineering standpoint, the design of a double connection is an efficient connection allowing for two beams on opposite sides of a column web to share the same set common connection bolts. However, from an ironworker connector’s standpoint, it can be a deadly design resulting in structural collapse, unless certain shop fabrication requirements are addressed. To attach the second member, the nuts on the first beams bolts must be removed and the bolt’s backed-out. This maneuver is extremely dangerous and often takes place with a connector sitting on the first member.
The Occupational Safety and Health Administration (OSHA) Subpart R – Steel Erection standard, drafted by three members of the IW and industry stakeholders, includes specific steel fabrication requirements to address the hazards double connections over column webs.
The following are two OSHA standards pertaining to steel fabrication of columns designed with double connections that provide specific requirements to prevent structural collapse during the erection process. It is important for our members, steel erection contractors and steel fabricators to recognize the potential structural collapse hazards associated with the double connection design, and the OSHA Subpart R – Steel Erection standards written to prevent this steel erection hazard. Our members and contractors must never erect columns that do not comply with the following OSHA standards:
CFR 1926.756(c)(1) – “When two structural members on opposite sides of a column web, or a beam web over a column, are connected sharing common connection holes, at least one bolt with its wrench-tight nut shall remain connected to the first member unless a shop-attached or field-attached seat or equivalent connection device is supplied with the member to secure the first member and prevent the column from being displaced (See Appendix H to this subpart for examples of equivalent connection devices).
CFR 1926.756(c)(2) – “If a seat or equivalent device is used, the seat (or device) shall be designed to support the load during the double connection process. It shall be adequately bolted or welded to both a supporting member and the first member before the nuts on the shared bolts are removed to make the double connection.”
The illustration to the left shows the erection of a typical double connection without any type of protective measures required by the above OSHA standard. Both of the nuts have been removed from the bolts and a spud wrench is used to help guide the second member into position over the bolts of the first beam. Connectors are sitting on the beam, not secured or protected from opening up, can collapse while trying to make the connection. Ironworkers must not erect double connections unless seat lugs or other devices are either shop or field attached to prevent collapse hazards. The use of come-alongs and/or half-pins to temporarily secure the beam to column connection during erection are not an acceptable method, or an alternative means to comply with the above OSHA standards.