Comparison of Bracings and Fluid Viscous Dampers in 15-Storey Buildings across All Seismic Zones of India under Bi-Directional Excitation

Abstract

An earthquake is a natural phenomenon i:e, sudden horizontal movement of earth’s crust that causes sudden collapse of buildings and other structures such as large monuments, bridges etc. The damage of the building is based on the amount of magnitude and intensity of the earthquake. A building can withstand in lower intensity of earthquake. But higher intensity causes lots of damages on building or a building can suddenly collapse and causes increase in number of deaths. To mitigate these effects a control system is to be provided such as base isolations, dampers, bracings etc. The current topic is based on the behavior of linear and non linear fluid viscous damper provided at center and both side corners of 15 Storey RC building in diagonally bracing system. The building is modeled and analyzed by using ETABS software. Here IS 1983(part1): 2002 and medium soil type are to be considered for analysis with respect to all seismic zones (zone II - zone V) of India. Here linear static and response spectrum analysis are applied in each model. Results are to be drawn based on base shear, storey displacement and storey drift to understand how fluid viscous dampers helps to reduce the effects of earthquake.

Introduction

I. INTRODUCTION

Fluid viscous dampers are the passive energy dissipation device which is provided in buildings to mitigate the effects caused by the earthquake. A fluid viscous damper consists of a cylinder filled with silicon oil, piston rod and orifice which is provided at piston head. When a building is subjected to seismic load, the piston rod which is provided in FVD moves against the fluid (silicon oil) and the fluid passes to another chamber of the cylinder through orifice. Since the silicon oil is thermal resistance, silicon oil reduces the effect of the heat due to the movement of the piston rod. Energy is dissipated by this mechanical function and this mechanical function creates resistance against the vibrations caused by the earthquake. The damping equation is given below.

???? = ????????????

Where:

F: damping force

C: coefficient of damping 

V: velocity

????: Damping exponent

II. OBJECTIVES OF THE PROJECT:

1. To know about the performance of the building with and without conventional bracings and FVDs in all seismic zones (zone II – zone V) of India subjected to bi-directional excitation condition.
2. To understand the effectiveness of linear and non linear FVDs in resisting the seismic load on buildings during earthquake.

III. METHODOLOGY

1. Before starting the project various journals are referred and objectives are finalized and confirmed.
2. 4 No’s 15 storey building models such as bare frame (building without any control systems), building with conventional bracings, building with linear FVDs (damper exponent = 0.3) and building with non linear FVD (damper exponent = 1.0) are carried out by using ETABS software.
3. Different loads such as dead load, live load, wind load and earthquake load as per Indian standards are adopted in analysis of the 15 storey models.
4. Linear static and response spectrum analysis are carried out in this project.
5. Results and conclusions are drawn with respect to displacement, base shear and storey drift.

IV. MODELING

A 15 storey reinforced cement concrete (RCC) building is analyzed by using ETABS software by applying linear static and response spectrum method. In this project all seismic zones of India are to be considered for analysis to determine the seismic response of building with bare frame, with bracings and with FVDs in all seismic zone condition.

Table 1: 15 storey model details:

Conclusion

The following conclusions are drawn below: 1) Seismic response values containing displacement, base shear and storey drift increases with respect to the seismic zones. 2) The maximum displacement and storey drift occurs in bare frame model. Therefore bare frame model exhibits low seismic resistance and high vulnerability to seismic damage. 3) Displacement is reduced in bracings in zone II and zone III. Whereas in FVD displacement reduced in zone IV and zone V. 4) Base shear is decreased in FVD compared to bracings. 5) Storey drift is also reduced in both bracings and FVDs compared to bare frame. 6) Both linear and non linear FVDs exhibits similar values in all seismic response values such as displacement, base shear and storey drifts. From the above conclusion, bracings are preferred for lower zones such as zone II and zone III. Whereas FVDs are preferred for higher zones such as zone IV and zone V. Therefore FVDs gives better performance compared to bracings during earthquake events.

References

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Copyright

Copyright © 2024 Akarsh A, GD Shivaraju. 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.