The “shaping workshop” experience provides designers direction on how to control the building movement of a super-tall, skinny skyscraper
Located in the center of Manhattan, 432 Park Avenue is the third tallest building in the U.S. and the tallest residential tower in the western hemisphere. More than twice the height any of its nearby neighbors, the 1396-foot (426m) structure is an expression of architect Rafael Viñoly’s vision of pure pragmatic form – a square shape, extruded straight into the sky, the exposed concrete simply and elegantly expressing pure structure.
When we began early on to work on the project, our first task was to discuss with the design team the special wind engineering challenges inherent in this tall, slender, prismatic structure. The 432 Park Avenue building’s exceptionally high height-to-width aspect ratio of 15:1 makes it very sensitive to vortex shedding, which introduces oscillating lateral forces as winds pass by. This was no surprise, as typically any structure with a height-to-width aspect ratio over approximately 4:1 is likely to face dynamic wind effects of this nature.
The team’s challenge then became to somehow ensure the building’s design would lessen the effect of the wind and ensure that acceptable occupant comfort would be maintained.
To do this, we brought together the owner, the architect, the structural engineer and our wind engineers to develop, review and test a variety of approaches.
After an initial gathering in a large motion simulator that enabled the team to experience the sort of motion being predicted for the structure, we agreed together on acceptable maximum motion parameters. Next, we spent a day together exploring the effects of individual architectural modifications as we tested more than a dozen scale models of the building in our wind tunnel – a process we refer to as a “Shaping Workshop”.
The strong commitment of both the architect and owner to maintaining a prismatic form led us to develop the concept of opening up some of the floors to allow wind to pass through the building, which would break up the coherence and effects of the vortices while preserving the structure’s purity of form.
Ultimately, we found that opening up two adjacent floors at five locations evenly spaced throughout the building height would provide the optimal arrangement. Working in concert with a pair of tuned mass dampers, which had already been agreed to as part of the solution, this achieved the necessary reduction in wind effects on the structure without compromising the architectural expression. The iconic structure now allows residents to enjoy their “estate living in the sky” in comfort as they appreciate the unique urban vistas below.