111 S Wacker Curtainwall Retension

Mortenson was selected to execute the highly complex re-tensioning of the cable-supported curtainwall system at the iconic 111 South Wacker office building. The cable-supported glass wall is one of a small number of similar systems installed in the City. By far the largest and most complex, it is the only such system in the US-installed in a curved application.

The initial phase of the project included significant work in the parking garage below the lobby in order to prepare for the re-tensioning work. Each cable in the system needed to be tensioned from an access point located below the lobby floor. Many of the access points were blocked by piping, ductwork, or other obstructions. Mortenson worked closely with the building engineers and staff to relocate systems to provide the required access. In addition, several columns and associated footings required augmentation to support the changes. Mortenson executed this work during off-hours to avoid disruption to building tenants.

The curtainwall work required close coordination and planning as the building was required to maintain normal operations during construction. Special care was taken to ensure the safety of both building occupants as well as pedestrian traffic on the busy streets. Significant temporary construction was required to protect the facility from the weather while the glass was being replaced.

The exterior wall of the building is constructed of a factory glazed, unitized, aluminum, and glass curtain wall system with exterior stainless steel fins on each mullion. The columns are also clad in stainless steel. The design of the curtainwall emphasizes the verticality and the structural expression of the building. The exterior glazed wall contains over 500 individual panes of glass. Each pane is a low-iron glass, treated with low-reflective coatings to maximize transparency. They are supported by 65 vertical cables extending over 50’ from the basement to the third floor. The panes of glass are installed vertically and corner clamped using steel patch fittings to keep them in place.