Floating Stair Using High Performance Structural Materials

In 2007 Walter P Moore relocated its corporate headquarters in Houston, TX, in 2007 to three floors in a tall building in downtown Houston designed by the firm. Working with the architecture firm Gensler, initial planning efforts identified the need to connect the workflow of the office via a new, common central stair atrium cut into the existing floor plates. The final design for the stair was chosen from an internal design competition that sought to identify a lightweight, progressive structural solution that highlighted the creative abilities of the firm. The design implemented for the stair consists of a cantilevered, stringerless arrangement that takes advantage of the intrinsic elements that exist functionally in a stair by rewriting the structural behavior of the stair through manipulation of the boundary support conditions. Using this design framework, individual elements of the stair were minimized through the use of high performance materials, including ultra-high performance fiber reinforced concrete (UHPFRC) and high strength steel cables. In addition to the optimization process that enabled the ultra-thin sections, a unique approach to vibration design was taken. The stair was intentionally designed to be somewhat flexible, allowing a platform for discussion of vibration perception topics with the clients who visit the office. The stairs are outfitted with a small tuned mass damper (TMD) and instrumented with accelerometers whose output is displayed on a large screen at the bottom of the stair.