Reduces unwanted swaying! Cantilevered Floor Walking Vibration Countermeasures
Cantilevered floor overhangs are prone to swaying, which can cause discomfort and loss of usability. The TMD vibration control device installed in the bosom of the ceiling can provide countermeasures without major design changes.
issue
Cantilevered floor overhangs are often problematic in terms of deflection and vibration, which can affect occupant performance.
In a certain S-structure office building, a cantilevered terrace with a 7-meter overhang was planned, and floor swaying during walking was a concern (Figure 1).
Figure 1.
counter-measure
Vibration countermeasures include ensuring sufficient beam rigidity or installing inter-columns at the ends. In this case, however, a vibration control device was used to suppress swaying without structural design changes, and a TMD with a mass of 500 kg was installed in the bosom of the ceiling (Figure 2) (Table 1).
Heel excitation was performed at the center of the span to check the natural frequencies. The floor was at 11.2 Hz, and the TMD frequency was adjusted accordingly (Figure 3).
Figure 2: TMD exterior (left) and installation (right)
Table 1: TMD basic specifications
Figure 3: Measurement results of response vibration acceleration when heel excitation is applied.
result
After installation of the TMD, two people walked in sync to confirm the vibration control effect. Vibration was reduced from 3.4 [cm/s2] when the TMD was not damped to 1.0 [cm/s2] after damping, a reduction of approximately 1/3 or less. In addition, the occupant environment has been greatly improved, with a rating of "not so bothersome" instead of "somewhat bothersome" according to the occupant performance evaluation criteria of the Architectural Institute of Japan (Figure 4).
Figure 4: Effects of TMD Measurement results during two-person resonant walking