Architecturally appealing monumental stairs can often translate into structurally flexible systems. Walking or running on such stairs may cause annoying vibrations. We have provided vibration design services for numerous monumental stairs with great success. We start by building a 3-D finite element model of the stair along with the structural floor framing that supports it. Next, we perform vibration analyses to uncover an optimal stair design that will meet established vibration criteria and also mitigate any adverse effect of vibrations on floor occupants.
The tenant desired to connect three floors through an elegant, spiral stair. Given the complex geometry of the stair, it was constructed from steel plates. The vibration design task was to construct a 3-D finite element model of the stair, including the connections to the floors, and to perform footfall vibration analysis. The required plate sizes were designed per the vibration analysis.
Maximum peak acceleration was selected as the monumental stair vibration criteria following the recommendations of the American Institute for Steel Construction, Design Guide – 11.
A finite element model (FEM) of the stair was built and enhanced vibration analyses were conducted with consideration for people ascending/descending the stair. Optimum plate sizes were determined while keeping the vibration levels below acceptable levels.
Just before the construction was complete, a quick vibration test opportunity was obtained. Measurements indicated that the model’s frequency estimate was within 1% of the measured stair frequency. Moreover, ascent/descent tests on the stair confirmed the estimated vibration levels per our detailed FEM.
The project included multiple monumental stairs. We highlight only the one with over 36 ft diagonal span supported by two side stringer beams.
Maximum peak acceleration was selected as monumental stair vibration criteria following the recommendations of the American Institute for Steel Construction.
A detailed finite element model of the stair was built and enhanced vibration analysis was conducted with consideration for both normal and rapid descents. Steel framing was efficiently updated to meet required vibration performance goals.
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