This is a case in which vibration from a fitness club was transmitted to a clinic, affecting medical equipment and the medical treatment environment, resulting in a complaint. We conducted a site survey, analyzed the cause based on vibration measurements, and proposed and implemented optimal countermeasures to reduce the experiential shaking that occurred at the clinic.

Engineering Group, Division 1

Jou Goki

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Issues in this case study

In recent years, floor vibration caused by fitness facilities in large commercial complexes and station buildings has increasingly led to environmental vibration problems for tenants on the upper or lower floors.
In particular, aerobics can cause resonance when the movement rhythm matches the swayable frequency of the subfloor floor, causing "uncomfortable swaying" in terms of occupant performance to the tenants below.

Also in this case study,
Exercise (aerobics) at 5th floor fitness club → Vibration propagated through building frame (beams, pillars, floor slabs) → Shaking felt at 4th floor clinic, disrupting medical treatment → Complaints generatedThis was the situation (Figure 1).

on-the-spot investigation

Floor vibration measurements were taken at the clinic (4th floor) during the time when the fitness club (5th floor) was conducting its regular program (dance and aerobic exercise).

The measured result is "between V-70 and V-90" when evaluated by the 2004 edition of "Occupant Performance Evaluation Guidelines for Building Vibration and its Commentary (2004) (Architectural Institute of Japan)" (Figure 2).
This means that approximately 70-90% of the people at the evaluation point will perceive the vibration, a condition that is difficult to tolerate in a medical environment where quietness is required. Especially in situations where the quality of communication is important, such as medical examinations and explanations, there is a possibility of complaints due to vibration problems.

Comparison of countermeasure methods

Several vibration countermeasures (source, transmission path, and receiving side) were compared for floor vibration transmitted to the 4th floor clinic (Table 1).

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Table 1 Comparison of proposed countermeasure studies

counter-measure	aim	Place of implementation	effect	cost	Construction Impact	matter of concern
(1) Operational support	Source Reduction	5th floor	Middle to High	–	–	Constraints on fitness operations
(2) Steel dry-type double floor	Fitness floor vibration reduction		Low to medium	amount of money	amount of money	Uncertain effect depending on floor level and frequency range
(3) Wet double floor			Low to medium	amount of money	amount of money	Uncertainty of effectiveness depending on frequency band, floor load-bearing issues, concrete curing days
(4) Addition of diagonal members	Clinic floor vibration reduction	4th floor	Low to medium	amount of money	amount of money	Restrictions on installation location
(5) TMD		Placed in the most effective locations	Middle to High	amount of money	amount of money	Installation location and floor load-bearing issues
6)AMD			amount of money	low	low	Installation location issues, AMD periodic maintenance required

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After comparing several alternatives, AMD (active mass damper) was selected for the following reasons

Installation cost about 1/5 of TMD
Low construction impact, and construction can be performed without stopping business.
Controls can follow changes in fitness program content and floor conditions

In addition, to eliminate customers' concerns about "Does it really work?" to address customers' concerns, we used a small AMD (mass weight 50[kg]) that can be transported by human power to conduct a temporary AMD installation demonstration at the site (Figure 3).

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Vibration-damping effect of AMD installation

Determination of natural frequencies

First, in order to determine the natural frequency of the floor, we conducted a heel impact excitation test and confirmed that the natural frequency of the fourth floor was 7.2 [Hz] (Figure 4).
Based on the measurement results, it was determined that the harmonic frequencies contained in the rhythm of fitness movements and the natural frequency of the floor were close, and that floor vibration was likely amplified by resonance.

Example: If the motion beat is about 2.4 [Hz] (about 2 to 3 steps per second)
　　Triple tuning = 2.4[Hz]×3 = 7.2[Hz] → Matches the natural frequency of the floor and tends to amplify shaking due to resonance.

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Installation of AMD - Confirmation of effectiveness

AMD is a vibration control device that produces force in response to floor shaking and effectively cancels vibration energy near resonance.
In this case study, the control frequency bandwidth was set and tuned for the natural frequency of the floor, 7.2 [Hz], and a demonstration unit was installed.

Subsequently, vibration measurements were taken on the fourth floor in the AMD OFF/ON conditions to confirm the vibration reduction effect of the fourth floor during aerobics on the fifth floor, and a comparative study was conducted (Figure 5).

From the measurement results, it was confirmed that the response near the natural frequency of the floor improved from "between V-70 and V-90" ⇒ "between V-50 and V-70" and became smaller when AMD was ON.
By realizing the vibration control effects through on-site demonstrations (effectiveness verification experiments), the customer's "uncertainty about the effects" was eliminated and they were able to proceed with their decision to install the equipment.

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summary

Vibrations in fitness facilities are greatly amplified when the building structure, natural frequencies, and exercise rhythms are combined, leading to discomfort and business disruption for tenants below.
In this case, based on precise vibration measurements and analysis of the causes, the optimal solution was selected from several countermeasure proposals, and the AMD vibration control system was installed to significantly reduce the clinic's perceived shaking.

In Yakumo,
On-site survey → Vibration measurement → Cause analysis → Countermeasure design → Construction → Confirmation of effectivenessWe can provide a full range of services, from
Also, to address concerns about the effectiveness of the measures,AMD's temporary demo (effectiveness verification experiment) is also availableThe Company has been working on this project for the past three years.

If you are having problems with fitness floor vibration, please feel free to contact us.

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