Seismic Analysis of Irregular Diaphragm Reinforced Concrete Building with Fluid Viscous Dampers

Abstract

Fluid viscous damper is the most commonly used tool for controlling structures’ responses. Fluid viscous dampers with different construction technologies are applied in order decrease the responses of structures to the seismic vibrations. During the recent years, controlling structure has turned into a scientific technology to protect structures against wind and earthquake loads. In the present study linear dynamic and non-linear static analysis was adopted to assess the seismic performance of an irregular diaphragm building. Building with and without fluid viscous damper have been taken.The outcomes of the study will be beneficial to assess the performance of existing building vulnerable to seismic loads after the installation of fluid viscous dampers.

Introduction

I. INTRODUCTION

The viscous fluid dampers (VFD) are the more applied tools for controlling responses of the structures. These tools are applied based on different construction technologies in order to decrease the structural responses to the seismic excitation. In last few years, many essential developments in seismic codes are turned up. Utmost of the modification in the seismic design area derive from greater awareness of actual poor buildings performances in contemporary earthquakes. Due to the renewed knowledge of the existing buildings behaviour, retrofit of buildings is a paramount task in reducing seismic risk. New techniques for protecting buildings against earthquake have been developed with the aim of improving their capacity. Seismic isolation and energy dissipation are widely recognized as effective protection techniques for reaching the performance objectives of modern codes. However, many codes include design specifications for seismically isolated buildings, while there is still need of improved rules for energy dissipation protective systems. When the structure has much absorbing capacity than the Seismic energy then it can withstand the structural damage. Equivalent viscous damping can be used as a feasible means of decreasing the structural damage. By absorbing seismic energy and reducing structural deformations, damper structures are designed and engineered to protect structural integrity, limit structural damages, and prevent injuries to residents. With the use of seismic dampers, a structure is able to withstand high input energy and reduce destructive deflections, stresses, and accelerations to its occupants and other structures. In FVD damper, by using viscous fluid inside a cylinder, energy is dissipated. Due to ease of installation, adaptability and coordination with other members also diversity in their sizes, viscous dampers have many applications in designing and retrofitting. In viscous dampers, a silicone-based fluid that circulates between a piston-cylinder configuration absorbs seismic energy. High-rise structures in seismic zones require viscous dampers. It can function in temperatures between 40 and 70 degrees Celsius. Strong winds and earthquakes both cause vibrations, which are reduced by viscous dampers. The term diaphragm discontinuity or irregularity refers to a diaphragm with a cut or open area that is greater than 50% of the gross diaphragm area or a sudden break or variation in stiffness that is greater than 50% in the effective diaphragm stiffness. Table 5 of IS 1893:2016, has explained the criteria of diaphragm irregularity. Opening in slabs causes flexible diaphragm behaviour, thus the frames and/or vertical elements do not share the lateral shear stress according to their lateral translational stiffness. When the opening is near the slab's edge, the issue is most severe. A few decades ago, the majority of residential and commercial buildings being developed tended to be simple, redundant constructions with lateral resisting systems that were informally structured. There were very few horizontal and vertical offsets in these buildings. The structural designs of many modern structures, on the other hand, demand for complicated lateral load paths that incorporate diaphragms at various elevations, several re-entrant corners, numerous irregularities, and fewer vertical lateral force-resisting features. To ensure complete load paths throughout the building, it is crucial to remedy these design flaws and inconsistencies, but doing so doesn't have to be difficult.

The main objectives of the study is to compare the seismic response of irregular diaphragm buildings, with and without fluid viscous damper at different locations.

II. METHODOLOGY

A. Model

In this study10 storey building having 3m storey height is taken for study. The geometry of the building is rectangular. The buildings are modelled on Etabs 2018 software. The code used for designing these buildings is IS 456:2000 “Code of practice for plain and reinforced concrete”, IS 1893:2002 “Criteria for earthquake resistant design of structures”. Following models and nomenclature have been used in the model to categorise different models used in this study.

1. IRDB - 10 storey diaphragm irregular building without FVD
2. IRDB - 2FVD - 10 storey diaphragm irregular building with FVD on 2 faces
3. IRDB - 4FVD - 10 storey diaphragm irregular building with FVD on 4 faces

Conclusion

Following are the conclusions of the study – 1) It has been concluded from the study that on incorporating fluid viscous damper in existing diaphragms irregular building will perform better during seismic excitation. 2) In between two side FVD and four side FVD arrangement, it has been found that four side FVD performs well in terms of seismic parameters along Y direction. For X direction, both FVD performs nearly same. 3) Storey drift reduces significantly in FVD building which means that chances of structural damages in partition wall will be less. 4) Although due to number and location of FVD, storey stiffness did not enhance significantly. 5) From the pushover results it has been concluded that on applying FVD in existing building, most hinges formed in elastic range as compared to without FVD building in which hinges are formed in collapse zone. 6) From the study, it has been concluded that although assembling FVD in existing building will incur cost but for high seismic zone, the seismic performance of diaphragm irregular structure will enhance.

References

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Copyright

Copyright © 2023 Abhay Trivedi, Dr. Gunjan Shrivastava, Kishor Patil. 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.