We recently read the October 2022 STRUCTURE article entitled “Fall Protection Anchorage Design Insights.” While the article covered a wide range of design considerations for fall protection anchorages, the article did not mention several important requirements and considerations that frequently govern the design of anchorages, including the following:
Since the 2015 edition, The International Building Code (IBC) has contained design requirements for certain fall protection anchorages in buildings and structures. Where the local jurisdiction adopts this IBC edition, or a later edition, these anchorages must be designed in accordance with the IBC. In the 2021 IBC, Section 1607.11.4 mandates that anchorages used for fall arrest, lifeline, and rope descent system purposes be designed for an unfactored live load of 3,100 pounds for each attached line, in any direction that the load can be applied. When the live load factor of 1.6 is applied to that load, the factored design load is 4,960 pounds, which is essentially equal to the 5,000-pound load for anchorages required by OSHA for each attached line.
The unfactored live load of 3,100 pounds is also included in Section 4.6.5 of ASCE/SEI 7-22, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. So even if a jurisdiction has not adopted the IBC, the minimum factored load for fall arrest, lifeline, and rope descent system anchorages is 4,960 pounds for each attached line in any direction that the load may be applied wherever ASCE 7-22 has been adopted.
OSHA has specific requirements for anchorages that are used to support rope descent systems (e.g., boatswain’s chairs and controlled descent apparatuses). According to Section 1910.27(b)(1)(i), anchorages for rope descent systems—which includes both the anchorages for the working lines and the anchorages for the personal fall arrest lines (a.k.a., “lifelines”)—must be “identified, tested, certified, and maintained [so they are] capable of supporting at least 5,000 pounds, in any direction, for each employee attached”. To put it more simply, any anchorages that are used for rope descent systems must be able to resist at least 5,000 pounds.
Although the author is correct that OSHA does permit some fall protection anchorages to be designed with a minimum factor of safety of 2.0 when “used under the supervision of a qualified person”, this is a very specific requirement. OSHA defines a qualified person as someone “who, by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training, and experience has successfully demonstrated the ability to solve or resolve problems relating to the subject matter, the work, or the project.” So, while OSHA might permit use of anchorages that have capacities less than 5,000 pounds for non-rope-descent-system uses, the users would have to be supervised by someone who meets the requirements of a qualified person. The cost of having a qualified person supervise workers using the anchorages will often eclipse any initial savings that might come from designing for a smaller design force.
Finally, although the designer could attempt to design some anchorages for 5,000 pounds and other anchorages for smaller forces, it is important to remember that workers typically cannot look at an anchorage years after a building is constructed and reverse-engineer the design to determine the original design criteria. Consequently, it generally makes sense to design anchorages for all purposes for which they may be used over their lifetime. In short, if it looks like an anchorage to which one could connect a lifeline or rope descent system line, it may very well be used for that purpose, no matter what the designer intended at the time of design.
For these reasons, unless the anchorages are only being used during construction of a building, we believe that most anchorages likely need to be designed for a minimum factored load of 5,000 pounds. Further, it is important that the minimum requirements in the International Building Code and/or ASCE 7-22 be followed wherever these codes and standards are legally adopted.■
Sincerely,
Gwenyth R. Searer, P.E., S.E.
Principal at Wiss, Janney, Elstner Associates, Inc.
Ms. Searer can be reached at gsearer@wje.com
Cole W. Graveen, P.E., S.E.
Senior Engineer at Raths, Raths & Johnson, Inc.
Mr. Graveen can be reached at cwgraveen@rrj.com
We have published a few articles in the past year or so on the design of supports and anchorages for exterior building maintenance equipment and fall protection systems. Most engineers probably don’t think about this issue much, but if one digs into the issue, it becomes quickly apparent that preparing a proper design is complicated due to overlapping provisions of the regulatory bodies, the IBC, and OSHA. The authors of our published articles didn’t agree on all design aspects and have very strong opinions on the subject. The STRUCTURE Editorial Board strongly supports a resolution of the conflicting opinions with code provisions that are clear, thorough, and located in one place.
—John Dal Pino, S.E., STRUCTURE Editorial Board Chair