Delicate hung curved glass stair which deals with significant movement issues in a high rise office building.
The stair at SandRidge was commissioned as a penthouse office centrepiece for the newly renovated SandRidge Energy headquarters in Oklahoma City. Stainless steel rods hang from the top of the double-height space carrying the stair which is split into four segments. Each segment is pinned to the next at the hanger locations which, along with the glass treads spanning between, work as a Vierendeel truss on plan. This on-plan truss provides lateral stiffness against seismic load which is considerable in the region, particularly on the 28th floor of a high rise providing lateral stiffness. Additional stiffness is provided along the underside of the stair by delicate rod cross-bracing forming a second truss beneath the Vierendeel. This also increases the natural frequency above pedestrian excitation levels to eliminate resonance under foot.
Various tricky movements, such as storey drift and variable hanger rod extensions, are accommodated through stainless steel fittings. These ostensibly simple connections splice the segmented panels and transfer all actions into simple point loads at the hanger connections. Local detailing prevents pinching and fatigue in the rods with headed ends and threaded sleeves which allow vertical adjustment of the stair to achieve a perfect level.