The large overhanging eaves also provide earthquake protection without changing the design!
A cantilevered structure such as an eave with a large overhang has a low natural frequency, so when an earthquake occurs, the amount of deformation becomes large, which may cause unexpected damage. Yacmo's TMD (vibration control device) reduces sway and ensures safety without requiring design changes.
issue
A certain commercial facility has a distinctive design with a large overhanging eave and glass curtain wall (Figure 1). Although there were no structural strength problems at the design stage, the natural frequency was low due to the large overhang of approximately 13 m, and there was concern that resonance during an earthquake would result in large deformation and possible damage to the glass and other finishes (Figure 2). Since there are stores under the eaves and people are walking around, it was decided to consider measures to prevent the eaves from swaying in case of an earthquake.
The following two conditions had to be met for the measures to be taken
- To suppress vertical vibration due to resonance between the eave ends and the center during earthquakes based on analysis
- Maintain design integrity without making design changes.
Figure 1: Exterior view of the building
Figure 2: Results of structural analysis
counter-measure
It was decided to incorporate the TMD into the structure as a measure to suppress the resonance of the eaves without structural design changes. Based on the results of the structural analysis, simulations were conducted to calculate the optimum adjustment values for the TMD to suppress vibration at 3.8 Hz at the eave ends and 13 Hz at the center. Based on the condition that no design changes would be made, the study was conducted to determine the size of the TMD that could be installed between the existing small beams and still produce a vibration-damping effect.
Simulation results show that a TMD with a mass mass of 360 kg at the eaves end and two TMDs with a mass mass of 120 kg at the center of the eaves will satisfy the sufficient effect (Figure 3).
Figure 3: TMD installation locations
Figure 3: TMD installation status
result
The effect of TMD reduces vibration at the eave ends and in the center. The vibration was reduced to less than 1/2 of that without measures, ensuring safety during earthquakes.
Figure 5: Displacement magnification of eaves before and after countermeasures
Related Pages
- added. This report compares AMD (Active Mass Damper) and TMD (Tuned Mass Damper), which are commonly used as vibration countermeasures for building floors, in terms of features, cost, and ease of maintenance. Please use this report when considering vibration countermeasures.
- Product Information TMD (Tuned Mass Damper)