Traffic vibration from the highway was transmitted to the office! Vibration Damping Devices to Countermeasure Later!
The office was experiencing problems due to traffic vibrations from the expressway, which caused the floor to shake significantly.
issue
Company A's office is a two-story steel-framed building, built under a highway (Figure 1). During heavy traffic hours, road traffic vibration was transmitted to the building, causing a vibration level (L10) of 68 dB on the floor of the second-floor office.
This is the level at which many people would notice the vibration. In addition, when evaluated based on the Occupant Performance Evaluation Guidelines (2004 edition), the results were much higher than V-90, which is an undesirable level for office use, and deterioration of the work environment was a problem.
Figure 1: Image of the building
Figure 2: Schematic diagram of the office
counter-measure
Since prior measurements had confirmed that floor vibration during vehicle passage was caused by resonance, we took measures with vibration control equipment, which is the most effective solution to the vibration problem caused by resonance.
Since the floor finish of the relevant office room was an OA floor with a 50 mm bosom, the Floormate (FM), an ultra-thin vibration control device with a thickness of 44 mm that can be installed under the OA floor, was adopted. This time, four units were installed, representing approximately 41 TP3T of the effective mass of the subject floor (Figure 3) (Figure 4).
Figure 3: Floor Mate Installation Figure 4: Floor Mate Installation Location
First, heel excitation was performed at the center of the floor to check the natural frequencies of the floor, which were 8.7 Hz, 9.3 Hz, and 16 Hz (Figure 5).
In order to achieve the optimum vibration control effect, the vibration frequency of the four FM units was tuned to three different patterns to confirm the effectiveness of each (Table 1). As a result, a vibration reduction of approximately 4 dB was confirmed in Case 2, and the occupant performance evaluation showed the greatest reduction, so the installation was tuned to Case 2.
Figure 5: Measurement results of response vibration acceleration when heel excitation is applied.
Table 1: Vibration level measurement results
result
The installation of the FMs resulted in a reduction of approximately 4 dB in the vibration level L10 value. In addition, the occupant performance evaluation of the building vibration was improved from V-90 to V-70 level, which is a good environment for office use.
Figure 6.Effects of FM Floor acceleration when vehicle passes
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