- Open Access
- Authors : Anu Rani N P, Sreerench Raghavu
- Paper ID : IJERTCONV10IS06069
- Volume & Issue : ICART – 2022 (Volume 10 – Issue 06)
- Published (First Online): 22-06-2022
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License: This work is licensed under a Creative Commons Attribution 4.0 International License
Seismic Performance Evaluation of RC Building Connected with and without X Braced Friction Damper using Etabs
Anu Rani N P
PG Student Department of Civil Engineering Mangalam College of Engineering,
Kottayam,India,
Sreerench Raghavu
Assistant Professor,
Department of Civil Engineering Mangalam College of Engineering Kottayam, India
AbstractAll the tall buildings are get affected by the seismic actions. So the buildings constructed in the earthquake zones are mainly designed considering seismic forces. The structures present in the higher earthquake zones are more liable to get more damages or collapse. To increase the safety of these structures few retrofitting techniques are used to stabilize against the earthquake force are done. Now a days damping devices are used to reduce the seismic energy and able to control the structural response of the building to the vibration. The advantages of using friction dampers over other types of energy dissipation devices are due to materials are less likely to be affected by degradation due to aging, materials are insensitive to changes in ambient temperature, there are no material yielding problems after a large earthquake and there are no fluid leaking. Previous studies have shown that tension-only braced frames provide more structural stability and hence offer better resistance when the frame is subjected to lateral loads. In comparison between braced frames, additional efficiency offered by the bracing depends on the selection of bracing system.
Key Words: Storey Building, Friction Damper, Storey Drift, Storey shear, Storey Stiffness, Friction Braced System, Overturning moment, Conventional Bracing System.
1. INTRODUCTION
In recent years, an efforts is being made to develop and improve the structural control devices to reduce seismic impact in the buildings. To achieve the concept of structural control the modification in the structural elements is carried out. To improve seismic response friction dampers is provided as X braces. They may be adjusted to decrease effects of loads under considerable level. To achieve the structural system in control many techniques have been adopted.
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Active Damping System 2) Passive Damping System
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Active Damping System
The active damping system is considered with large external power source that may vary from ten kilowatt to several mega watt . The structure can be adopted to add or dissipate seismic energy. The energy required by the active system is very large. It is difficult as it is expensive and less reliable. Full scale implementation of Active structural control is used in Japan, USA, Taiwan, China.
Active damping system 1) Active brace system 2) Active mass damper system 3) Active tendon system.
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Passive Damping System
It is a device that is attached to the structure which may by designed to modify in damping or stiffness in a structure without requiring an external power in an appropriate manner to operate. Passive damping system includes 1) Tuned Mass Dampers 2) Magnetic Dampers 3) Viscous Dampers 4) Yielding Dampers 5) Friction Dampers
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Tuned Mass Damper, also known as vibration absorbers or vibration dampers , is a passive control device mounted on a specific location in a structure so as to reduce the amplitude of vibration to an acceptable level whenever a strong lateral force such as an earthquake or high winds hits. The application of tuned mass damper can prevent discomfort, damage or outright structural failure. They are frequently used in power transmission, automobile, and tall buildings.
Fig 1.1 Tuned Mass Damper
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Magnetic damper consists of two racks , two pinions , a copper disk and rare earth magnet. This type of damper is neither expensive nor dependent on temperature . Magnetic damping is not strengthen that is why it is effective in dynamic vibration absorbers which requires less damping.
Fig 1.2 Magnetic damper
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In Viscous dampers seismic energy is absorbed by silicone based fluid passing between piston cylinder arrangement. They are used in high rise buildings in seismic areas. It can operate over an ambient temperature ranging from 40 to 70. Viscous damper reduce the vibration induced by both strong wind and earthquake.
Fig 1.3 Viscous damper
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Yielding dampers or metallic yielding energy dissipation device is manufactured from easily yielded metal alloy materials. It dissipates energy through its plastic deformation which converts vibratory energy and consequently declines the damage to the primary structural elements. Yielding dampers are economical, effective and proved to be a good energy dissipater.
Fig 1.4 Yielding damper
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Friction damper device consist of several steel plates sliding against each other in opposite directions. The steel plates are separated by shims of friction pad materials. The damper dissipates energy by means of friction between the surfaces which are rubbing against each other. It is also
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possible to manufacture surfaces from materials other than steel.
Fig 1.5 Friction damper
2 METHODOLOGY
This research involves the various analysis techniques to determine the lateral forces ranging from purely linear to non-linear inelastic analysis. In India the Standardized method of analysis is followed by using a code IS1893 (Part 1):2002 Criteria for Earthquake resistant design of structures. The seismic performance of building connected with and without friction dampers is carried out.
Table 2.1: The loading combinations are
Sl.No |
Load Combination Details |
1 |
1.5DL |
2 |
1.5DL+1.5LL |
3 |
1.2DL+1.2LL+1.2EQX |
4 |
1.2DL+1.2LL+1.2EQY |
5 |
1.2DL+1.2LL-1.2EQY |
6 |
1.5DL+1.5EQX |
7 |
1.5DL-1.5EQX |
8 |
1.5DL+1.5EQY |
9 |
1.5DL-1.5EQY |
10 |
0.9DL+1.5EQX |
11 |
0.9DL-1.5EQX |
12 |
0.9DL+1.5EQY |
13 |
0.9DL-1.5EQY |
3 MODELLING AND ANALYSIS
The primary purpose of structural analysis of building structures is to establish the distribution of internal forces and moments over the whole or part of a structure and to identify the critical design conditions at all sections. The geometry is commonly idealized by considering the structure to be made up of linear elements and plane two-dimensional elements. The program ETABS is employed herein to perform nonlinear dynamic time history analysis to obtain the modal characteristics
3.1 Modelling of conventional bracing
The conventional bracings are modelled using steel tubes . Both linear properties are provided for the bracer. The linear properties are used for the linear modal load case.
PROPERTY NAME |
TUBE450X250X20 |
MATERIAL |
Fe250 |
SHAPE |
STEEL TUBE |
DEPTH |
450mm |
WIDTH |
250mm |
FLANGE THICKNESS |
25mm |
WEB THICKNESS |
25mm |
WEIGHT |
Table 3.1.1 Braces section details for 12 story building
3.3Modelling of RC structure
In the finite element analysis software ETABS, building is idealized as an assemblage of area, line and point objects. Those objects are used to represent members like wall, floor, column, beam, and brace and link/spring.
A 12 storey RCC special moment resistant framed structure is considered as the case study model. The building plan and elevation as shown in figures 3.1 and 3.2 respectively. The plan is symmetrical in shape and having an area measurement of 37.5×37.5 m2. The total height of the building is 36 m. each story has a height of 3m including ground floor. The base is fixed to restrain in all 6 DOFs.
Table 3.3.1 Beam and Column details of 12 story building
3.2 Modelling of friction damper
Friction brake is widely used to extract kinetic energy from a moving body as it is the most effective, reliable and economical mean to dissipate energy. For centuries, mechanical engineers have successfully used this concept to control motion of machinery and automobiles. This principle of friction brake inspired the development of friction dampers.
The friction dampers are modelled using two-joint link elements (Plastic Wen). Both linear and nonlinear properties are provided for the dampers. The linear properties are used for the linear modal load case and the nonlinear properties are used for the nonlinear time history load cases.
PROPERTY NAME |
FD |
MASS kg |
2200 |
WEIGHT kN |
0.225 |
EFFECTIVE STIFFNESS kN/m |
20000 |
EFFECTIVE DAMPING kN-s/m |
4000 |
TYPE |
EXPONENTIAL |
DIRECTION |
U1 |
NON-LINEAR |
NO |
Table 3.2.1 FD details for 12 story building
PROPERTY NAME |
MATERIAL |
SECTION SHAPE |
DEPTH |
WIDTH |
B250*450 M25 |
M25 Fe415 |
RECTANG ULAR |
250 |
450 |
C 600*600 M25 |
M25 Fe415 |
SQUARE |
600 |
600 |
Table 3.3.2 Slab details of 12 story building
PROPERTY NAME |
MATERIAL |
THICKNESS |
S150 , M25 |
M25, Fe415 |
150mm |
Fig 3.1 Plan of the building
Fig 3.2 3D view of a 12 storey building with friction damper
4 RESULTS
This section defines about detail discussions of software results of different building models with and without BRBs. Comparative study of all types of building models are discussed with respect to storey shear, storey deflection, storey drift and time period etc
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Maximum Storey displacement (mm)
Model
Displacement, EQX
Displacement EQY
Conventional Bracing System
22.51
22.51
FrictionDamper System
28.5
28.5
Model
Storey Drift, EQX
Storey Drift EQY
Conventional Bracing System
0.000747
0.000747
FrictionDamper System
0.00189
0.00187
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Storey Drift
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Overturning Moment (kN-m)
Model
Overturning Moment, EQX
Overturning Moment EQY
Conventional Bracing System
72229
72228.68
FrictionDamper System
67168
67594.49
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Storey Stiffness(kN/m)
Model |
Storey Stiffness, EQX |
Storey Stiffness, EQY |
Conventional Bracing System |
2720330 |
2720330 |
FrictionDamper System |
848152 |
859763 |
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CONCLUSION
The seismic performance of a reinforced concrete (RC) building structure was evaluated and concluded that the structure can be strengthened by incorporating friction dampers.
The response parameters such as maximum storey displacement, storey drift, storey shear, overturning moment and storey stiffness are compared for both structures with and without friction dampers. The storey displacement is increased due to introduction of friction dampers as the energy dissipation . The storey drift of the building including the friction damper system is increased slightly. The storey shear
,overturning moment and storey stiffness of the building including the friction damper system is reduced.
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REFERENCES
4.3 Storey Shear (kN)
Model |
Storey Shear, EQX |
Storey Shear EQY |
Conventional Bracing System |
2521.78 |
2521.78 |
FrictionDamper System |
2408.32 |
2424.60 |