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  • Writer's pictureMAREJ

Know Your Davits Before You Hang

By Alexis Herr, P.E., ECS Mid-Atlantic, LLC

Roof-anchor testing and certification is a critical part of maintaining the rope-descent system or suspended-scaffold system used to access the exterior façade on buildings. Per the Walking-Working Surfaces standard, 29 CFR Part 1910, Subpart D & I, OSHA requires anchors for rope descent be capable of maintaining a 5,000-pound load in any direction. The industry-standard test for common U-bar anchors is to test anchors against each other with a chain hoist, which is simple, but effective.

However, as architectural-design trends push toward buildings with roof amenities, decorative screen walls, sunshades and other features, standard U-bar anchors, and standard testing methods, don’t always work.

Many rope-decent systems use specialty anchors such as recessed roof anchors (hidden under pavers), drop-through anchors or outriggers to accommodate design features on a building’s roof. Some systems rely on suspended scaffolds, also called swing stages or powered platforms. When testing specialty-access systems, the certifying engineer must use their understanding of the system to ensure the test replicates the required load on the anchorage points.

In particular, if your goal is to avoid hanging large weights from the side of a tall building, testing davit-base systems that include tall masts and long arms to support suspended scaffolds requires foresight and understanding of the load path.

One such system exists on Atlantic City’s MGM Tower at Borgata, formerly known as the Water Club. Built in 2008, the MGM Tower is a 38-story building with decorative screen walls and signage on its roof. In 2022, the building was set to undergo a large glass-restoration project. To access the building façade, an elaborate davit system was used to suspend swing stages. The davits were fitted with tall masts and arms up to 11 feet in length. The most unique aspect of this system may be that the davit bases were not stationary but motorized and mounted on a tripod-shaped base that rolled along two tracks.

Challenges for testing this system included difficulty accessing and setting up the davits, testing equipment in limited space and providing a load test that distributed the test loads correctly between all of the system’s components and dual tracks while ensuring that the worst-case system and track locations were tested.

ECS Mid-Atlantic, the firm selected for the testing, worked closely with the restoration contractor, Clean & Polish Building Solutions, and with the building engineers to test and certify the davit system. Great care was taken in setting the davits at points along the track which were the most vulnerable. Attention was paid to designing testing procedures that would replicate the in-service load on the arms, mast, base and dual-track systems.

In addition to the davits, secondary tie off points (U-bars) were not provided as frequently as needed, so the team identified, tested and certified additional anchorage points to be used to secure safety lines.

With proper certification, the building is now accessible for future maintenance and restoration projects completed by swing-stage platform scaffolds, rope-descent systems and industrial rope-access methods.

After testing was completed, the system was deemed to be safe to use for the glass-restoration project. The MGM Tower now stands as a glimmering silhouette in the Atlantic City skyline.

Alexis Herr, P.E. is vice president, principal engineer for ECS Mid-Atlantic, LLC.

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