Developing a New Installation Method for Unitized Curtain Walls

The unitized curtain walls_* used in skyscrapers eliminate the need for on-site glass work and similar tasks, which makes a significant contribution to shortening the construction period. However, in order to install units weighing over 500 kg, or even 1,000 kg in some cases, on the exterior of a building, it is essential to choose the most appropriate installation method for each site. Each installation method, whether it uses a monorail hoist, floor crane, forklift, "Curtain Walker” robot , or tower crane, has its own advantages and disadvantages, and so the installation method used is tailored to the characteristics of the building.

* A curtain wall with glass and boards built in at the factory and assembled into a unit

With a monorail hoist, the hoist from which the curtain wall is suspended moves on rails. This allows it to move horizontally in front of the columns, and is not affected by the environment inside the installation site, and as such, ease of installation is a key point in this method’s favor. However, a tower crane is required to reposition the hoist (i.e., to move the apparatus to higher floors), and because this work must be carried out by specialist contractors, it can be very expensive. Other issues include the fact that the rail itself constitutes a heavy load. In light of these properties of monorail hoists, we developed a "Simplified Monorail System" to enable us to do all the work in-house.

The Simplified Monorail System involves attaching a light and strong aluminum rail to the fastener_*1 used to secure the unitized curtain wall, and passing a pulley through the rail, allowing the curtain wall to be moved as it would be on a monorail. The lightweighting of the rails has improved ease of operation, allowing us to perform the repositioning work in-house.
The aluminum rails themselves are also manufactured by YKK AP. To design a rail capable of holding curtain wall units that can weigh over 1 ton, we began with the design of the extrusion profile, experimenting with different shapes and thicknesses, as well as the size of the rollers inside the rail. It is vital that, in the unlikely event that a rail becomes damaged, the curtain wall hanging on the outside of the building is not dropped. After repeated testing and revisions of the shape, it was confirmed that a rail with a load capacity of 600 kg_*2 would not break even when subjected to a load of 3,500 kg. This Simplified Monorail System, which is lightweight, sturdy, and allows for smooth lateral movement, was developed over a period of one and a half years. This technological development takes full advantage of YKK AP’s integrated production system, which allows the company to perform everything from aluminum extrusion and processing to product development and installation in-house.
The Simple Monorail System has been patented as a system, including not only the rails but also the mounting configuration.

*1 A component part of both the frame and the curtain wall, which is used to join the two together

*2 Per pulley of a hoist

To date, we have conducted three installations using the Simplified Monorail System. Although the aluminum rails are temporary fixtures that will eventually be removed and disposed of, in one case the uppermost aluminum rail was painted and utilized as part of the building’s external design. This is not only beneficial from the perspective of environmental protection, namely by reducing waste, but can also be used for maintenance purposes, such as replacing glass.
In addition, the use of tower cranes, which are prioritized for use in steel frame assembly operations during the day, can be minimized, allowing curtain wall installation work to be performed during the day rather than at night. This will contribute to labor shortage countermeasures and work style reform in the construction industry.