There are seismic, vibration isolation and damping structure in the structure to resist earthquakes. The seismic system is designed to increase the stiffness of a structure, so that the structure can resist the earthquake load when an earthquake dissipates the seismic energy through the damage of the structural member. Cracks and residual deformation remain in the structural members, and the amount of secondary damage because of the repair and reinforcement after the earthquake is significantly increased. Instead of the seismic design with these problems, there is an increasing interest in the vibration isolation and damping structure. The damping structure is a concept to dissipate the earthquake energy through a damper when an earthquake occurs by installing a damper with damping performance on the existing structure. Most of the earthquake energy is dissipated by the damper, and the damage to the structure is reduced. Among various types of dampers, a type of energy-dissipating damper, which is economical and has excellent vibration control effect, is most commonly used; in particular, a steel damper is widely used. However, the existing dampers are expensive and made of steel plates, so the damper is heavy, requires a lot of equipment and manpower during installation, and requires a large work space. In this study, we propose a viscoelastic panel damper (VPD), which improves the disadvantages of the damper.
The proposed VPD has three fiber reinforced polymer(FRP) plates and two viscoelastic materials, which are arranged in the longitudinal direction, and the shape that absorbs the vibration energy is identical to that of the conventional damper. However, using FRP, the weight of the damper is reduced, so the damper can be constructed without a complicated process with few people. In addition, the construction time is shortened by simplifying the damper shape and construction procedure, and maintenance is facilitated. To verify the performance of the proposed vibration dampers, a small shaking-table test was performed before the large shaking-table test to confirm the performance improvement of the real-scale structure reinforced with the proposed VPD. In the small shaking-table test, the GFRP with a 6:4 longitudinal/transverse ratio of glass fiber and urethane rubber was used. In the large shaking table test and static test, the GFRP with a 9:1 longitudinal/transverse ratio of glass fiber and 3M viscoelastic materials was used. In the small shaking-table test, sine wave was used. The test results show that the maximum acceleration, maximum displacement, maximum interstory displacement and maximum strain of the specimens with VPD significantly reduced. In the large shaking-table test, the observed seismic waves were used. The test results show that the maximum acceleration increased, and the maximum interstory displacement decreased. The maximum displacement decreased, but the decrement was not significant. In the large shaking-table test, the performance improvement by VPD was not as clear as that of the small shaking-table test. To verify the structural behavior of the VPD system, a static test was performed.
In the static test, the damper shape and damper installation were identical to those in the large shaking-table test. We experimentally confirmed that the damper exhibited an out-of-plane behavior without the in-plane behavior during the displacement load operation because of the combined effect of the damper installation method and holes. The damper hole of the damper was not sufficiently fixed by the hole breakage. When the damper is installed, the damper should be fixed so that left and right movements do not occur, so the shear behavior of the viscoelastic material should be possible. However, the damper was not sufficiently restrained, and the shear behavior was not obtained. Therefore, the FRP plate appears to behave as one plate and does not show a large damping effect in the large shaking-table test.
Based on the large shaking-table experiment, the analytical model was computerized and compared with the experimental results. Then, the damping effect according to the shape of the VPD was analytically confirmed. A numerical analysis was performed using ABAQUS, and the steel frame structure was modeled in three dimensions to be identical to the large shaking-table test using the identical material properties as the actual material. The width, thickness, and material properties of the viscoelastic material were analyzed based on the VPD specification in the large shaking-table test. As a result, the maximum interstory displacement of the structure was most sensitive to the width of the viscoelastic material. The shear modulus converges to a constant value above a certain value. The analysis based on the VPD specification in the large shaking-table test shows that the efficiency of the damper was high when the shear modulus was 10 MPa, the width was 8 mm or the thickness was 60 mm.