Long-span steel-frame staircase shakes and makes you uneasy! Ultra-thin vibration suppressor Floormate improves swaying when walking!
Design tends to be important for staircases at entrances and halls. Staircases with a high design quality often have a slim framework, which tends to sway easily and may give a sense of fear to pedestrians. In such cases, Yacmo's low-profile vibration suppressor "Floormate" can improve walking comfort and reduce the sense of fear caused by extreme shaking.
issue
Steel materials are used for steel staircases with a high design quality. This is because a staircase with a clean appearance can be designed to blend in with the space even more. However, because the components are slimmer instead of lighter, the staircase may sway more, causing anxiety and fear for people going up and down the staircase and for those standing still.
A steel staircase was planned to be installed in the atrium of a university building in a reconstruction project.
The building had a 9-meter span between the first and second floor beams, with a straight staircase with no support columns, creating an open space with no sense of oppression (Fig. 1). The construction company approached us to consult on the installation of a vibration control system on the steel-framed straight staircase.
Figure 1: Cross-sectional image of staircase
counter-measure
As a result of discussions with the construction company and design office, it was decided to install the damping device on the back side of the treads without changing any components or adding any supports so as not to spoil the design of the staircase, since this staircase is a straight staircase without a landing. Yacmo's low-profile damping device "Floor Mate" is extremely thin (44 mm thick) and has a cantilevered structure with a movable mass, so it can be installed diagonally on the back side of the treads as in this case.
Figure 2: Appearance of the vibration control device Floor Mate
Table 1: Basic Specifications of Vibration Damping Equipment
TMD-type vibration control devices such as FLOORMATE require the natural frequency of the TMD mass to be in tune with the swayable frequency (natural frequency) of the object whose vibration is to be suppressed.
First, to determine the natural frequency of the staircase, we measured the response acceleration of the staircase by human excitation (heel excitation) and performed a frequency analysis (FFT analysis). As shown in Figure 3, we found that the natural frequency of the staircase is 6.9 Hz, which has a peak.
Figure 3: Results of FFT analysis during heel excitation
After adjusting the frequency of the floor mates to match the natural frequency of the staircase, they were installed behind the staircase (treads) (Figure 4).
Figure 4: Installation of vibration control equipment
Figure 5: Measurement location diagram and Floor Mate installation location diagram
result
After the floor-mate was installed, measurements were conducted to confirm the vibration control effect by two people walking in unison in the non-vibration control state (TMD OFF) and in the vibration control state (TMD ON). A metronome was used to maintain a constant pace during the two-person synchronized walking vibration test. The results are shown in Figure 6. When the vibration was not controlled, the vibration level was 37.7 cm/s in the 1/3-octave band at 6.3 Hz, which is close to the natural frequency of the staircase.2was 11.0 cm/s after vibration control.2and was reduced to about 1/3 (about -10dB). Figure 6 depicts the occupant performance evaluation curve*1 and the pedestrian bridge guideline*2 as vibration evaluation curves, but since this case is a staircase and not an occupant space, the latter was used to evaluate the vibration (Table 2). As shown in Table 2, the results show that the Floormate has successfully improved the swaying when ascending and descending, with people in a walking state going from "I feel it a little" to "I feel it a little less than a little" and people in a standing state going from "I clearly feel it" to "I feel it a little.
*1 "AIJES-V0001-2004, Environmental Standard of the Architectural Institute of Japan, Guideline for Occupant Performance Evaluation of Building Vibration and its Commentary".
2 "Pedestrian Bridges in the Future - Guidelines for Planning and Design of Pedestrian Bridges that are Attached and People-Friendly" Japan Steel Construction Association, ed.
Figure 6: Measured results of effectiveness confirmation by two-person synchronized walking (occupant performance evaluation curve and pedestrian bridge design guidelines)
Table 2: Comparison of evaluation before and after vibration control using pedestrian bridge design guidelines
Related Pages
- Product Information] Floor Mate
- Case Study] Improved uncomfortable shaking and walking feeling of steel-frame staircases! Ultra-thin vibration-damping device Floormate reduces vibration without compromising staircase design!