< PreviousTHE USE OF ALUMINUM CREATES A BRIGHT CENTERPIECE AMIDST THE DARK ATRIUM DEPTHS AND UNIFORMITY BETWEEN NEW ELEMENTS IN THE MUTED SPACEp/ 21 Case Study — Synergi LLC Synergi’s design-assist team found the uniquely metallic and bright look of aluminum with an orbital finish to be the optimal material for the double-helix staircase Material Selection The staircase was conceptually inspired by paper folding art principles where a single strip forms the flight of risers, and it provides a stark visual contrast to the adjacent demis- ing wall. Synergi’s design-assist team suggested that the uniquely metallic and bright look of aluminum with an orbital finish could be the optimal material for the double-helix stair- case for its slim profile and visual lightness, as well as its ability to create a fluid shape. Aiming for the bright, lustrous appearance of metallic steel, using this finished non-ferrous metal on all elements of the stairs forms a bright center- piece amidst the dark atrium depths and creates uniformity between all the new elements – many of which are stainless steel – in the muted space. Utilizing Structural Steel Laid across the rooftop, a series of parallel steel beams span the atrium’s opening from east to west, creating a frame to anchor the two interwoven stairs. Much like two opposing wind forces rush at each other and interlock, spiraling and eventually funneling downwards into a tornado, two steel beams on opposite sides of the atrium arch towards each other, circling one another where they meet at the center and connect to a structure of steel columns and appear to seamlessly transition downwards into interwoven coils of stairs that wrap around each other. The steel beams cre- ate a frame that anchors the vertical HSS columns around which the stairs are installed. A steel structure was installed to support the interwo- ven stairs and the connecting landings, modelled as (4) HSS12x12 columns. Located in the atrium’s center, the col- umns of the HSS tower are bolted to the floor at the bottom with conventional baseplates. A ring of stiff beams between the ends of the columns at the top qualifies the columns as fixed on the top and bottom for vibrational considerations. This also enables the structure to achieve vibration beyond what is recommended despite the slenderness of the center HSS support structure (4.4Hz – greater than the minimum natural frequency of 4.0 Hz recommended for serviceability).— Post Houston p/ 22 2023 Design Innovations & Modifications Rather than actual spirals, the stairs’ curved shape is cre- ated by straight runs with curved outer edges - the string- ers. The initial drawings call for three straight stringers clad in a metal “shell” to create the exterior curvature and steps. As typical structural components encased in finished mate- rials, these steel stair stringers are usually unfinished. In Synergi’s modified design, the treads are laid directly onto the three sawtooth stringers, utilizing the structural treads to double as the finished material. The outer of these three stringers is curved to reflect the design intent of curved dou- ble-helix stairs. Rather than cladding the stringers, Synergi opted to put a special orbital finish on all exposed aluminum members, essentially exposing the structural elements but giving them a “finished” look for OMA’s vision. The stairs were designed to be supported by the central steel columns. To accomplish the stairs’ look of floating off the HSS structural tower, 8x8x½” size outriggers were utilized at each stair run and additionally at each landing and hidden within the decorative cladding at the underside. Outriggers were integrated into the design and shop-inserted into the stair structure, welded to the plate stringers. The primary plate stringers were situated at the midway, inboard, and outboard sides of the stair and exposed to view with a deco- rative orbital finish providing a uniform look with the rest of the structure and also supporting the unique box-framed stainless steel mesh guardrail. An intermediate stringer was utilized to support the center of the stair treads of the stair, the varied width reaching up to a remarkable 7’ 10”. initial drawings depicting a typical stair segment with claddingp/ 23 Case Study — Synergi LLC WITH A CURVED OUTER STRINGER AND AN ORBITAL FINISH, THE EXPOSED ALUMINUM STRUCTURAL ELEMENTS DOUBLE AS FINISHED MATERIAL IN SYNERGI'S MODEL. RATHER THAN ACTUAL SPIRALS, THE STAIRS’ CURVED SHAPE IS CREATED BY STRAIGHT RUNS WITH CURVED OUTER EDGES. Synergi's modified design— Post Houston p/ 24 2023 p/ 25 Case Study — Synergi LLC Constructability Review & Analysis Conscious of the tight timeline, an analysis of the project’s constructability determined that modular construction of the stairs would facilitate transport to the job site and expedite onsite installation. When installed by crane, modular stair units have to consider the weight limitations of the particular equipment. The density of steel gives it considerable weight; thus, the steel stair – as it was originally planned – would have to be fabricated and assem- bled in components small and light enough to be handled by a crane. Considerably lighter than steel, Synergi found that re- placing the steel with aluminum allowed the modular size of the units to maximized. As demonstrated by the engineered logistics plans, using a structural alu- minum system for the stairs offered a less complex process and greater installation efficiency – result- ing in safer rigging and minimal onsite welding. Replacing steel with aluminum – a lighter metal – allowed for larger, prefabricated modular units.— Post Houston p/ 26 2023 Uncovering a significant installation issue when attempting to install or replace bulbs, Synergi provided recommendations for smaller and more cost-effective lighting solutions. Synergi fabricated the finalized BIM model into a full-scale mockup, which was reviewed multiple times to fine-tune the design, especially the mesh and lighting details.p/ 27 Case Study — Synergi LLC A key aspect of the O stair’s design, integral lighting sets within the mesh on each individual post of the guardrail contribute to the striking “chandelier look” of the stair. To finalize the design and continue work on the project, a BIM model of a mock-up was shared with the team for review, comment, and redesign as needed. Synergi fabricated the finalized BIM model into a full-scale mockup, including the cladding, which was set up at Synergi’s Mockup Studio. As the project continued, Synergi participated in full BIM co- ordination with the GC and other critical subcontractors for this project, verifying the design with the structural model and other trades where interactions occur – such as land- ing and bridge transitions on the second floor, which had to be coordinated with Powers Brown Architecture and the precast subcontractor. The mock-up was reviewed multiple times via video calls to fine-tune the mesh and lighting de- tails especially. Initially, the mesh guardrail was to be installed as sections of panels on one side, made removable using several small screws to be able to replace the bulbs of the integrated lighting system. In building the mock-up, Synergi’s team uncovered a significant installation issue when attempting to install or replace bulbs: the original bulbs were discovered to be close to the same size as the opening in the mesh guardrail. Replacing the mesh guardrail panel required pre- cise alignment of tiny components, especially the wiring; the smallest misplacement could unintentionally cut or injure occupants and maintenance staff or snag their clothing – not to mention take away from the clean lines of the design. To demonstrate the sizing issue of the original lighting design and to determine its impracticality the preconstruc- tion department's Virtual Design & Construction Team performed and recorded a timed lighting installation and re- placement test on the full-scale mockup, dutifully acting out the replacement process step-by-step. The video-recorded test concluded that, by using the originally selected bulb, the replacement of just one light bulb would take 26 minutes. Over the long term, this could prove both time-consuming and costly in terms of ongoing maintenance. Synergi pro- vided recommendations for smaller and more cost-effective lighting solutions that wouldn’t require removable panels of guardrail, and a tube of light of light with a smaller diameter was selected. A FULL-SCALE MOCKUP OF THE RAILING OF THE “O” STAIR'S RAILING WAS BUILT TO “PREVIEW” THE DESIGN AND MATERIAL QUALITY AND ENSURE IT MET THE EXACTING STANDARDS OF ALL PARTIES INVOLVED.Next >