June 2015

Stabilizing Cantilevered Members to Prevent Structural Collapse

Structural collapse during steel erection continues to be one of the “Deadly-Dozen” hazards and the failure to stabilize cantilevered structural members is one of them. When buildings or structures are designed with cantilevered members, preplanning is necessary to determine what temporary support or erection aids are needed to prevent structural collapse during the erection process. 

When the field connections for cantilevered members are designed with bolted holes and/or welded connections, it is often necessary to temporarily support the structural members until the entire connection has been completed. Erection aids for support and to maintain stability are commonly specified for cantilevered connections, but in some cases such specifications may not be denoted. It is important to check the shop and erection drawings denoting erection aids and specific instructions for the steel erection contractor. The preference for erection aids and procedures may vary from area to area and from company to company.

The drawing on the right is a typical cantilevered member that is shop fabricated with lugs for using turnbuckles to support and position the cantilevered beam until the connection is completed. Other methods to provide temporary support may include the combination of wire rope slings and come-a-longs, or the use of vertical shoring beneath the cantilevered members.

Because the steel erector is the party who actually erects the steel, they are responsible for determining the type and strength of the aids. The American Institute of Steel Construction (AISC) Code of Standard Practice provides guidance regarding this type of responsibility pertaining to cantilevered members. This can be discussed at the preconstruction meeting between the steel erector and the fabricator. Afterwards they can coordinate with the engineer of record and the architect regarding the appropriate erection aids to be used. In any case, the type of erection aids for cantilevered members must be made prior to proceeding with the fabrication and detailing process.

The following is the standard from the AISC Code of Standard Practice pertaining to the responsibility for the erection and stability of cantilevered members.

1. OSHA Subpart R – Steel Erection 1926.756(a)(2)
“A competent person shall determine if more than two bolts are necessary to ensure the stability of cantilevered members; if additional bolts are needed, they shall be installed.”
Note: The OSHA definition of a competent person is: “one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.”

2. OSHA Subpart R – Steel Erection 1926.756(a)(1)
“During the final placing of solid web structural members, the load shall not be released from the hoisting line until the members are secured with at least two bolts per connection, of the same size and strength as shown in the erection drawings, drawn up wrench-tight or the equivalent as specified by the project structural engineer of record, except as specified in paragraph (b) of this section.”
Note: Whenever cantilevered beams are part of the building or structure design, it is important to check the erection drawings for specifications by the project structural engineer of record.

3. OSHA Subpart R – Steel Erection 1926.754(a) 
“Structural stability shall be maintained at all times during the erection process.”

Note: This is a more general OSHA standard but still requires that structural stability be maintained at all times, including cantilevered members.

The International Association will continue our “ZERO INCIDENT FATALITY CAMPAIGN” in 2015 to increase safety performance and help protect our members in the field and shop. This goal challenges all members to “See Something! Say Something!” to help recognize and avoid workplace hazards. Structural collapse during steel erection continues to be one of the “Deadly Dozen” hazards, and the failure to stabilize cantilevered structural members is one of them. Jeff Norris, Canadian safety coordinator and I will continue to work closely with district councils, local unions, and IMPACT regional advisory boards throughout the United States and Canada to help improve safety performance. If I can provide any assistance, please contact me at the Safety and Health Department at (800) 368-0105. If you require assistance in Canada, please contact Jeff Norris, Canadian safety coordinator at (780) 717-0071.