In a city known primarily for buildings that adhere to traditional, pragmatic building design, the smooth curves and glass façade of 727 West Madison is drawing welcome attention for bringing a unique, modern style to Chicago’s West Loop neighborhood.

“The building is distinctive with its elliptical shape and spiral-patterned cladding,” said Chris Arjona, project manager for WSP USA. “It is a highly sculptural building and has a striking, patterned façade that contributes greatly to the aesthetic of the neighborhood and to the western views of the skyline. The curved shape provides great views all around.”

Reaching nearly 500 feet in height, Chicago’s newest luxury rental tower not only provides stunning views of downtown Chicago and Lake Michigan for those inside in the building, but for passersby its eye-catching design is equally difficult to ignore.

727 West Madison is now the tallest building in the West Loop, as well as the tallest building in Chicago west of the Kennedy Expressway. It is located in a narrow strip between the Kennedy Expressway and the edge of the areas zoned for taller buildings, ensuring that it will be highly visible from both sides for many years to come.

WSP began its design work in February 2016 and was completed in June 2018. Construction began in February 2017 and by the time the grand opening was held in June 2019, it had already achieved 80 percent occupancy of its 492 one-, two- and three-bedroom units. The property developer is F & F Realty and Fifield.

Collaborating with the architect, FitzGerald Associates Architects, WSP designed a structure that provided the performance required with minimal impact to room layouts and the façade. The design included sufficient stiffness for motion-perception comfort in the top penthouse unit under predicted wind storms.

“At the upper levels, the shear walls were set along demising walls between units so as not to encroach in the units themselves,” Arjona said. “On the parking garage podium at the lower levels, many of those walls drop off to allow for the parking ramp to pass through.”

As a building with such an unusual design, it brought with it some challenges, both anticipated and unexpected.

The building’s elliptical floor plate required an approach that differed from traditional rectangular, straight-sided floors. Understandably, this presented a challenge in laying out the post-tensioned cables, which typically run at right angles to one another and the slab edge.

“We worked with the general contractor and the post-tensioned cable supplier to develop details where the post-tensioned tendons hit the slab edge at varying angles using stock, angled pocket formers rather than custom pieces to minimize cost,” Arjona said. “The post-tensioned design was highly efficient, requiring minimal reinforcement thanks for early collaboration with the architect and studies to set optimal column spacing coordinated with the unit layouts.”

He anticipates that this project will serve as a good standard of how post-tensioning can be used for curved floor plates. “WSP developed a scheme that was highly efficient and allowed the contractor to maintain its aggressive three-day pour cycles on the tower floors.”

In a place famously known as “The Windy City”, one of the challenges designers had to address was identified during an early wind tunnel study of the building and its location.

“As the tallest building on the western edge of downtown Chicago, it is not shielded from the prevailing winds from the west by any other buildings or geographic features,” Arjona said. “Wind tunnel studies showed that a building one block north of 727 West Madison would shed wind onto the building in the form of vortices that would impact and buffer the north face of our building and twist the structure.”

The result of this discovery was the need to design for wind loads higher than standard code and to further strengthen the tower so it would be capable of resisting this torsional wind phenomena. By identifying the issue early in the design phase, it was addressed with no impact to the unit layouts, the views from the residential units, or to the garage ramp through specific rebar detailing and the addition of two structural walls hidden in some unoccupied spaces and along storage rooms near the base.

“Use of a rational structural layout maintained a high level of symmetry within the early-coordinated unit layouts,” he added.

The building foundations used a hybrid system of belled caissons (bearing on soil) under shorter podium columns, and straight shaft (bearing on rock) caissons under tower columns. WSP performed numerous studies that examined the predicted settlement of the foundations and shortening of the columns to make sure that the hybrid system would not affect the long-term performance of the structure.

“Sizes of the foundation elements were calibrated to give similar settlement behavior and keep the settlement performance consistent across the plan despite the use of different systems,” Arjona said.

Due to the high visibility of the project, 727 West Madison is recognized as an important contribution to the Chicago skyline.

“With its site directly next to a major interstate in downtown, thousands of commuters pass this building every day and it is fast becoming a noted landmark in the city,” Arjona said. “Its distinct look and high visibility from all views of the city from the west help as well.”

He said one of the keys to the project’s completion on a relatively short timeline was a good relationship with the architect.

“WSP was involved early to comment on the initial unit layouts and how they would affect the locations of the structure,” Arjona said. “This early collaboration with the architect led to unit layouts that fit very well with the most efficient structural layout and kept the structure efficient, lowered the cost, and kept columns and walls from impeding into unit spaces and views.”

He was grateful to play a key role on a building that is well on its way to being recognized as a signature feature on the Chicago cityscape.

“As a Chicago resident and father of two small girls growing up in the city, I’m proud to have contributed to the famous Chicago skyline,” he said. “I like to point the building out to them and show them what ‘Da-Da’ worked on.”

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