straight staircase / metal frame / concrete steps / without risers
CABLE-DUCTAL® VIERENDEEL TRUSS by Gensler & Walter P. Moore
When Walter P. Moore and Associates Inc., decided to relocate in Houston, Texas, the firm took the opportunity to show-off their engineering prowess with a unique Cable-Ductal® Vierendeel Truss design -- extensively modeled (in finite element) using SAP 2000 software. A time-history dynamic analysis was conducted under a simulated footfall stair loading that included modeling of the Tuned Mass Damper (TMD) and springs. The entire structure weighs 6 tons and is cantilevered by the "floating" Vierendeel truss, which is not connected to the lower landing.
The individual, Z-shaped Ductal® stair treads are .75m x 2.21m x 0.025m thick, with a compressive strength of 20,000 psi. The treads, manufactured by Lafarge Precast in Winnipeg, Canada, were cast in an enclosed form with a textile liner to provide a non-skid walking surface.
The engineers installed a vibration absorber (TMD) between the first and second units at the bottom for motion control and vibration absorption. The structure is instrumented with wireless sensors to a nearby computer and screen so that displacement amplitudes and accelerations may be monitored and graphically visualized in real time.
Architectural design was provided by Gensler and engineering (erection design, planning and field consultation) was performed by Walter P. Moore.