Structural Behaviour of Friction Dampers and Isolation Techniques for Seismic Vibration Control of Buildings

Abstract

Studies on the methods to mitigate the effects of earthquake on structures has gained up pace since the last four decades with the invention of base isolation techniques and then the energy dissipating seismic devices. Here in this work an effort has been made to study the effects of Lead Rubber Bearing (LRB) as base isolator and Friction Dampers as energy dissipating devices when installed individually and when as a dual combination in the eight storey ‘C’ shaped building considered by the use of ETABS software. The building is assumed to be located in earthquake zone 4 and the method of seismic analysis chosen is linear Response Spectrum analysis. The response parameters that are studied in this work are time period, base shear, storey displacement and storey drifts. The results show that these devices have improved seismic resistance of the building by decreasing the responses of the structure when included as individually and when as a combined control strategy. The improved results are in comparison with the conventional model.

Introduction

• Earthquake: Sudden shaking of the Earth's surface due to underground fault movement, generating seismic waves, which are highly destructive.

• Modern structures, especially high-rise buildings, are increasingly vulnerable due to their height and complexity.

• The most efficient design minimizes both loss of life and structural damage.

• Earthquakes are unpredictable in time and location, posing major safety and economic challenges.

• Historical data shows that structural collapse is a major cause of fatalities during earthquakes, emphasizing the need for seismically designed buildings (residential, historical, industrial, etc.).

2. Objectives of the Study

The study focuses on evaluating the seismic performance of a C-shaped reinforced concrete (RC) structure using various seismic mitigation systems:

1. Perform Response Spectrum Analysis on a C-shaped RC building using ETABS.

2. Design and implement Lead Rubber Bearings (LRB) for base isolation and assess their impact.

3. Study the effect of Friction Dampers on seismic response.

4. Analyze the dual system: LRB + Friction Dampers.

5. Compare four models using parameters like time period, base shear, storey displacement, and storey drift.

3. Base Isolation and Friction Dampers

A. Base Isolation

• Decouples the structure from ground motion using flexible isolation elements installed at the foundation.

• Widely used in earthquake-prone zones, especially for buildings and bridges.

• Reduces seismic energy transfer, prevents resonance, and enhances serviceability.

B. Lead Rubber Bearings (LRB)

• Invented in New Zealand (1975).

• Composed of steel plates, rubber layers, and a lead core.

• Steel provides vertical support; rubber allows lateral flexibility.

• The lead core adds damping and stiffness.

• Well-established for high-stiffness and large-deformation scenarios.

C. Friction Dampers

• Passive energy-dissipation devices activated by earthquake motion.

• Moving parts slide and generate friction, absorbing seismic energy.

• Increases building stiffness and reduces vibration.

• No external energy needed; activated purely by seismic input.

• Made with materials like lead-bronze, Teflon, or stainless steel.

4. Methodology and Structural Model

A. Software & Model

• Analysis performed using ETABS.

• Structure: 8-storey C-shaped RC building.

• Dimensions: 40m x 20m, 5 bays in X and Y directions.

• Material:

  • Concrete: M30

  • Steel: Fe500

• Elements:

  • Columns: 350x450 mm

  • Beams: 300x450 mm

  • Slab: 150 mm thick

B. Load Specifications (as per IS standards):

C. Seismic Parameters (IS 1893:2016):

5. Modelling LRB and Dampers in ETABS

• Steps to model LRB:

  • Go to: Define > Section > Link/Support Properties

  • Define base isolation support and point springs

  • Assign LRBs at the base of all columns (Z+ axial direction)

6. Comparative Study (Four Models Analyzed)

• Parameters for comparison:

  • Time Period

  • Base Shear

  • Storey Displacement

  • Storey Drift

Conclusion

1) The seismic control methods that are used, base isolation (LRB) and Friction Dampers (FD) have effectively reduced the response parameters caused due to earthquake. 2) With the incorporation of LRB at base of the building, has increased time period to an extent of 44.50%, with only FDs reduced time period to 35.12% and upon the inclusion of both LRB and FDs, have resulted in increase of time period to 24.24% on comparing with time period of first mode of conventional model which is fixed base and without dampers. 3) When LRBs are introduced at the base of building, it has reduced the base shear values of 35.43% in X and 31.09% in Y directions. With the inclusion of only FDs in the model, base shear values have increased to an extent of 41.35% in X and 54.44% in Y direction. But in the combined control strategy, that is LRB with FD, the base shear values decrease to 27.25% in X and 19.51% in Y direction as compared with conventional model. 4) The maximum storey displacement values decrease to an extent of 16.68% in X and 25.56% in Y direction for the model with FDs. For the model with LRB, the maximum storey displacements increase to an extent of 23.47% in X and 20.42% in Y directions. For the model with both LRB and FDs there is increase of 8.95% in X and 2.27% in Y directions as compared with conventional case. In the model with LRB and in the model with both LRB and FDs, shows some little displacement at base level to an extent of 25 mm in X and 34 mm in Y, which is zero in case of fixed base building. 5) The storey drift values significantly decrease in all the models with LRB, with FDs and even in the dual system that is with both LRB and FDs as compared with conventional building. 6) The storey drift values have reduced to an extent of 25% in X and 37% in Y directions for model with FDs. Those drift values have decreased to 35% and 32% in both X and Y directions for model with LRB and to 64% in the case of model with both LRB and FDs in both X and Y directions as compared with conventional case. 7) The decrease in storey drifts in the case of combined strategy, that is with LRB and FDs, is because of the seismic energy dissipation and increased stiffness of the structure due to both LRB and FDs. Hence this combined control strategy can be adopted to mitigate the effects of earthquake.

References

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Copyright

Copyright © 2025 Athram Venkatesh , Dr. Abhishek Kamishetty . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.