Greater Cincinnati’s newest riverfront icon, The Ascent at Robeling Bridge in Covington is a 22 storey luxury condominium tower project comprising 62 units that was inspired by the Ohio River and the Roebling Suspension Bridge. Its signature arcing profile and curved walls reaching, twisting, stretching, spiralling upward in motion is an unusual concept in building, posing a considerable challenge when it comes to window cleaning and exterior building maintenance using suspended equipment. We shouldn’t be surprised at this original work of art, since Daniel Libeskind was the architect chosen for the new Freedom Tower in New York City, another unique landmark building with some unusual features.
Pro-Bel Technical Approach
This novel building is definitely one of Pro-Bel’s more interesting challenges. The Pro-Bel engineers’ first tasks were to provide safe horizontal movement over the entire steeply pitched roof. This was achieved using 8 separate fully engineered horizontal cable lifeline systems that provided a safe means of access to, and egress from, work zones i.e. once at a work zone, the worker can tie off to a separate fall protection system and/or access primary rigging equipment. In this instance, suspended maintenance workers will travel to the edges of the roof (that have low or non-existent parapets) and clip onto their respective u-bar lifeline and suspension anchors, spotted around the top of the roof, for travel down the side of the building using a roof rigged bosun’s chair or ground rigged platform. Unusually, almost all of the roof anchors on The Ascent roof were either horizontal (at the roof edges) or sloped (on the field of the roof), a rather special situation.
To make things even more interesting, three faces of the curved building were angled (and slightly curved vertically!) from top to bottom, not unlike the leaning tower of Pisa. To ensure workers could access the inward angle faces of the building, a vertical down-rigged line or “standing line” with a tensioning device anchored a ground level or pool level, was used from top to bottom of the building at appropriate horizontal intervals. After hooking up suspension lines at roof level, the platform is picked up at ground level, hoisted to roof level using the standing- line for stability. As the platform is lowered, at every second floor, the workers can access a wall anchor (using a hook) to pull themselves a few feet towards the wall. When finished window cleaning/maintenance, they reverse the procedure to roof level and then ride back down using the standing-line again for stability which is removed upon completion of maintenance activities. When not in use, the standing-line anchors at ground level are concealed using metal cover plates.
Other types of u-bar safety anchors used on the project included concealed terrace anchors, soffit anchors and some vertical roof anchors. All in all, definitely one of Pro’Bel’s more interesting window cleaning/exterior building maintenance projects.