Figure 1 The TMDs being commissioned and fine-tuned
To effectively address the vibration issues of a monumental staircase in a healthcare educational facility, DEICON supplied and three tuned mass dampers (TMDs) and have them integrated into the structure. The TMDs were designed and calibrated to target the first bending mode of vibration of the staircase, thereby significantly enhancing its stability and ensuring a comfortable and safe environment for users.
Monumental staircases are breathtaking with their own unique serviceability challenges. As architects create slender and complex forms, vibrations induced by people climbing up and down the stairs are a growing concern. These subtle movements can ripple through the stairs and into other parts of the building, causing discomfort for occupants.
The structural engineers of the project modeled the staircase and predicted the dynamic attributes of the monumental staircase, namely the first natural frequency and mode shape of the structure; this animation illustrates the first mode. To verify the predicted first natural frequency and estimate the inherent damping in the structure, DEICON carried out extensive vibration measurements. The verified first natural frequency was used in tuning the tuned mass dampers, targeting the first mode of vibration of the staircase.
The blue traces in Figure 2 depict the measured landing acceleration and estimated damping of the staircase without the TMDs. The red traces in Figure 2 show the same information, except with the TMDs installed.
The comparison of the red and blue traces in Figure 2 clearly demonstrates the effectiveness of the tuned mass dampers. They increased damping in the target mode nearly sixfold, from 1.6% to 9.5%, significantly reducing the staircase’s vibrations.
Figure 2 Measured vibration without and with the TMDs
Other monumental staircase vibration control applications include, but are not limited to: