SEISMIC RESPONSE CONTROL OF ASYMMETRIC BUILDING USING VISCO-ELASTIC DAMPER

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1 International INTERNATIONAL Journal of Civil Engineering JOURNAL and Technology OF CIVIL (IJCIET), ENGINEERING ISSN AND (Print), TECHNOLOGY (IJCIET) ISSN (Print) ISSN (Online) Volume 5, Issue 12, December (2014), pp IAEME: Journal Impact Factor (2014): (Calculated by GISI) IJCIET IAEME SEISMIC RESPONSE CONTROL OF ASYMMETRIC BUILDING USING VISCO-ELASTIC DAMPER Vidhi Patel 1, Abhijitsinh Parmar 2, Mittal Patel 3, Urita Mehta 4 1 Asst.Prof, Dept. of Civil Engg, SVBIT, Gandhinagar, India, 2 Asst.Prof, Dept. of Civil Engg, SVBIT, India, 3 Asst.Prof, Dept. of Civil Engg, SVBIT, Gandhinagar, India, 4 Asst.Prof, Dept. of Civil Engg, SVBIT, Gandhinagar, India, ABSTRACT Earthquakes are one of the most destructive of natural hazards. Earthquake occurs due to sudden transient motion of the ground as a result of release of elastic energy in a matter of few seconds. The impact of the event is most traumatic because it affects large area, occurs all on a sudden and unpredictable. They can cause large scale loss of life and property. Hundreds of small earthquake occurs around the world every day. Some of them are so minor that humans cannot feel them, but seismographs and other sensitive machines can record them. Buildings being one of the prime structures for mankind, it is necessary that they are designed to resist earthquake forces. In past earthquake events worldwide, it was observed that building with regular shape, size and geometry has performed well as compared to building with H,C,L,T and + shaped buildings. Therefore, it is important to control structural response of asymmetric buildings when subjected to earthquake ground motion. In order to control structural response of building basic technologies are used to impart additional stiffness in the building. These basic technologies are Base Isolation, Passive Energy Dissipation Devices and Active Control Devices. The main objective of this paper is to control the seismic response of asymmetric building having Regular shape, C shape, L shape and T shape subjected to four different types of earthquake ground motions namely Elcentro, Kobe, Northridge and Loma Prieta using Visco-elastic dampers. A three storey building is considered and designed is done using E-Tabs software and various response quantities like displacement, acceleration and inter-storey drift are extracted. Comparison of buildings with visco-elastic damper is done with that of uncontrolled building. It is observed that controlled building shows moderate range of reduction for all response quantities as compared to uncontrolled building. 282

2 I. INTRODUCTION Earthquakes are one of the major natural hazards and responsible for the lives of thousands of people and damage to the structures. Buildings being one of the prime structures for mankind, it is necessary that they are designed to resist earthquake forces. Strong ground motion observations have been carried out in Japan since 1953 at universities, government agencies, industries etc. However, it was only in 1962 that a strong motion earthquake observation council (SMEOC) was established with a view to providing basic guidelines in obtaining strong motion records on a national scale and also providing smooth exchange of information between various agencies on strong motion records. Seismic response controlled structures are being accepted as a fresh concept that can respond to the needs of a society in the new century. Structural control is one area of current research that looks promising in attaining reduce structural vibrations during loadings such as earthquakes and strong winds. The reducing of structural vibrations occurs by adding a mechanical system that is installed in a structure. The present study is concerned with the control of the seismic response of asymmetric buildings. It has been observed that during strong earthquakes asymmetric structures are more affected and leads to more damage than symmetric building. Asymmetric building means that the centre of mass and centre of rigidity are not located at the same point. Various structural vibration techniques are used to control vibration like base isolation system, passive control system, active control system, semi-active control system and hybrid control system. The main objective of structural control devices is to reduce structural vibrations that occurs due to earthquakes and strong winds. In this paper main objectives is to study response reduction of the building subjected to various earthquake excitations using visco-elastic dampers. In this research a three storey asymmetric building having Regular shape, C shape,l shape and T shape is considered and designed using E-Tabs software. Uncontrolled response and controlled response of asymmetric buildings using visco-elastic damper are obtained. quantities obtained for uncontrolled and controlled buildings are compared to know the performance of visco-elastic damper. II. VISCO-ELASTIC DAMPER Viscoelastic dampers (VED) are highly effective in mitigating the dynamic responses of building structures due to wind or seismic excitation, and practically were used in the twin towers of the World Trade Center in New York for the reduction of wind-induced vibrations. This damper is designed on the basis of energy dissipation due to shear deformation in solids. The damper as shown in Fig.3 consists of the plates between which the polymer materials have been filled and kinetic energy is wasted with the shear deformation of the polymer layers, so that viscoelastic material has a polymer molecule structure and in other words, their molecules are linked together as chain. As the result of the molecular network above, viscoelastic material shows a resistance against the deformation. In fact, stiffness of structural systems will be increased by using this material in the structure. On the other hand, while deformation is applied to this material, some of the molecular bonds are broken down and the heat is produced, depending on temperature and the loading frequency. So, some energy is spent to break the bonds, and is wasted. Damping of these materials is due to the breakdown of intermolecular bond. After loading over time, the material recovers their initial strength, which the amount of this recovery depends on the temperature of the material, stimulant frequency and strain amplitude. In short, one will face an increase in stiffness and damping in the structural system by using the material above in the structure. In viscoelastic dampers, shear storage modulus and shear loss modulus are function of the main vibration frequency of structure, and are used to determine the effective stiffness and damping. 283

k d = AG'/t..(1) C d = AG''/ ωt.. (2) G' = 16.0ω 0.51 γ -0.23 e (72.46/Temperature) G" = 18.5ω 0.51 γ -0.20 e (73.

3 k d = AG'/t..(1) C d = AG''/ ωt.. (2) G' = 16.0ω 0.51 γ e (72.46/Temperature) G" = 18.5ω 0.51 γ e (73.89/Temperature) where A = area of the damper, t = thickness of one layer of visco-elastic material, ω = natural frequency of the structure, k d = damper stiffness, C d = damping co-efficient, G ' = shear storage modulus and G" = shear loss modulus. III. PROBLEM A three storey asymmetric building with following geometric dimension is considered to assess the efficacy of visco-elastic damper in controlling the seismic response of asymmetric building having Regular shape, C shape, L shape and T shape. No. of storey = 3 Storey height = 3m Slab thickness = 120 mm No. of Bays in X-Direction = 4 No. of Bays in Y-Direction = 3 Bay Width in X-Direction = 5m Bay Width in Y-Direction = 4m Beam Size = 230mm 400mm Column Size = 350mm 350mm f ck = 25 N/mm 2 f y = 415 N/mm 2 L.L. = 3 kn/m 2.F. = 1.5 kn/m 2 The building is subjected to four earthquake ground motions Elcentro, Kobe, Northridge and Loma Prieta earthquake. The plan and 3D view of the building having Regular shape, C shape, L shape and T shape with above mentioned geometry is shown in fig. 1, fig. 2, fig. 3 and fig. 4 below. Fig. 1 Plan and 3-D View of Regular Shape Building 284

Fig. 2 Plan and 3-D View of C Shape Building Fig.

damper placed at ground floor is shown in Fig.

4 Fig. 2 Plan and 3-D View of C Shape Building Fig. 3 Plan and 3-D View of L Shape Building Fig. 4 Plan and 3-D View of T Shape Building Shear model of the Regular shape building with visco-elastic damper placed at ground floor is shown in Fig.5 which are subjected to four earthquake ground motions using E-Tabs software. 285

5 Fig. 5 Building With Visco-Elastic Damper at Ground Floor The ground acceleration time history for Elcentro, Kobe, Northridge and Loma Prieta is as shown in Fig.6 below. Fig. 6 Ground Acceleration Time History for Various Type of Earthquakes 286

6 IV. RESULTS AND DISCUSSIONS quantities of uncontrolled shear building under four types of earthquake excitations i.e. ElCentro, Kobe, Northridge and Loma Prieta are obtained. Table 1, Table 2, Table 3 and Table 4 shows peak(i.e. maximum) response quantities(displacement, inter-storey drift and acceleration) obtained for uncontrolled building having Regular shape, C shape, L shape and T shape under all the earthquake excitations considered. TABLE 1: Quantities for Uncontrolled Building Having Regular Shape Displ. (m) Inter- storey Accel. (m/s 2 ) TABLE 2: Quantities for Uncontrolled Building Having C Shape Displ.(m) Accel. (m/s 2 ) TABLE 3: Quantities for Uncontrolled Building Having L Shape Displ. (m) Accel. (m/s 2 )

7 TABLE 4: Quantities for Uncontrolled Building Having T Shape Displ.(m) Accel.(m/s 2 ) It is seen that from Table I to Table IV that displacement and acceleration occurs maximum at top storey of the building, however maximum inter-storey drift occurs at second storey for all the earthquake excitations. It is clearly seen from Table I to Table IV that all response quantities is least for El Centro earthquake excitation but highest for Northridge earthquake excitation. Table V to Table VIII shows response quantities extracted for asymmetric buildings having Regular shape, C shape, L shape and T shape with visco-elastic damper under four different types of earthquake excitation. The value of damper stiffness and damping co-efficient is obtained by using Equation (1) and (2). TABLE 5: Quantities for Controlled Building Having Regular Shape Displ.(m) Accel. (m/s 2 ) TABLE 6: Quantities for Controlled Building Having C Shape Displ.(m) Accel. (m/s 2 )

8 TABLE 7: Quantities for Controlled Building Having L Shape Displ. (m) Accel. (m/s 2 ) TABLE 8: Quantities for Controlled Building Having T Shape Displ. (m) Accel. (m/s 2 ) It is seen from Table 5 to Table 8 that visco-elastic damper is effective in controlling structural response of asymmetric building having Regular, C, L and T shape. Reduction in interstorey drift at first, second and third storey in Regular shape building, C shape building, L shape building and T shape building in X-direction is 82.05%, 63.34%, 56.13%,83.85, 64.40%, 57.73%,83.01%, 63.62%, 56.71%, 84.01%, 63.08% and 55.94% respectively as compared to uncontrolled response under Elcentro excitation. Similarly, reduction in peak inter-storey drift for Regular shape building, C shape building, L shape building and T shape building under Kobe earthquake excitations are 77.83%, 52.40%, 46.24%, 82.62%, 62.05%, 57.21%, 81.02%, 59.13%, 53.95%, 84.66%, 66.41% and 61.74% under Northridge earthquake excitations are 78.31%, 48.60%, 38.97%, 79.15%, 49.37%, 38.32%, 78.37%, 48.49%, 37.53%, 78.87%, 48.65% and 37.86% and under Loma Prieta earthquake excitations are 84.76%, 66.83%, 61.52%, 85.18%,65.12%, 61.80%, 84.17%, 64.46%, 59.62%, 85.92%, 67.27% and 62.45% respectively across all stories. Reduction in inter-storey drift at first, second and third storey in Regular shape building, C shape building, L shape building and T shape building in Y-direction is 80.75%, 62.29%, 55.74%, 82.11%, 61.79%, 55.35%, 80.85%, 60.85%, 54.60%, 71.91%, 56.94% and 52.44% respectively as compared to uncontrolled response under Elcentro excitation. Similarly, reduction in peak inter-storey drift for Regular shape building, C shape building, L shape building and T shape building under Kobe earthquake excitations are 79.16, 58.78%, 53.77%, 84.66%, 69.08%, 65.44%, 81.38%, 63.53%, 78.69%, 75.85%, 63.88% and 61.09% under Northridge earthquake excitations are 75.42%, 46.24%, 36.25%, 75.98%, 46.95%, 37.96%, 74.80%, 45.72%, 36.51%, 62.82%, 41.37% and 35.79% and under Loma Prieta earthquake excitations are 82.28%, 63.20, 58.24%, 84.57%, 66.94%, 62.87%, 82.88%, 64.52%, 59.92%, 75.39%, 61.64% and 58.19% respectively across all stories. 289

9 Peak displacements response also shows similar reduction for controlled building with respect to uncontrolled building under Elcentro earthquake excitation. Reduction in displacement at first, second and third storey in Regular shape building, C shape building, L shape building and T shape building in X-direction is 82.05%, 71.28%, 67.16%, 83.85%, 72.78%, 68.65%, 83.01%, 72.21%, 67.82%, 84.01%, 72.04% and 67.67% respectively as compared to uncontrolled response under Elcentro excitation. Reduction in displacement for Regular shape building, C shape building, L shape building and T shape building under Kobe earthquake excitations are 77.83%, 63.37%, 58.76%, 82.62%, 70.94%, 67.22%, 81.02%, 68.62%, 64.69%, 84.66%, 74.31% and 70.92% under Northridge earthquake excitations are 78.31%, 62.04%, 55.93%, 79.15%, 62.86%, 56.57%, 78.37%, 62.12%, 55.85%, 78.87%, 62.08% and 55.87% and under Loma prieta earthquake excitations are 84.76%, 74.70%, 71.27%, 85.18%, 74.55%, 70.99%, 84.17%, 73.16%, 69.39%, 85.92%, 75.51% and 71.92% respectively across all stories of controlled building as compared to uncontrolled building. Reduction in displacement at first, second and third storey in Regular shape building, C shape building, L shape building and T shape building in Y-direction is 80.75%, 70.30%, 66.42%, 82.11%, 70.68%, 66.67%, 80.85%, 69.61%, 65.66%, 71.91%, 63.33% and 60.42% respectively as compared to uncontrolled response under Elcentro excitation. Reduction in displacement for Regular shape building, C shape building, L shape building and T shape building under Kobe earthquake reductions observed are 79.16%, 67.72%, 64.07%, 84.66%, 75.97%, 73.27%, 81.38%, 71.40%, 73.27%,75.85%, 69.16% and 67.10% under Northridge earthquake excitations are 75.42%, 59.73%, 53.70%, 75.98%, 60.11%, 54.46%, 74.80%, 59.08%, 53.23%, 62.82%, 51.13% and 46.86% and under Loma Prieta earthquake excitations are 82.28%, 71.80%, 68.12%, 84.57%, 74.94%, 71.69%, 82.88%, 72.82%, 69.36%, 75.39%, 67.84% and 65.20% respectively across all stories of controlled building as compared to uncontrolled building. Peak acceleration response of controlled building shows less reduction compared to other response quantities. Reduction in acceleration at first, second and third storey in Regular shape building, C shape building, L shape building and T shape building in X-direction is 61.90%, 55.47%, 56.35%, 69.88%, 60.29%, 62.62%, 60.06%, 51.74%, 55.76%, 73.96%, 62.34% and 61.38% respectively as compared to uncontrolled response under Elcentro excitation. Reduction in acceleration for Regular shape building, C shape building, L shape building and T shape building under Kobe earthquake excitations are 73.41%, 64.64%, 52.51%, 78.88%, 65.68%, 62.71%, 76.83%, 63.14%, 59.89%, 80.03%, 69.82% and 63.26% under Northridge earthquake excitations are 57.17%, 21.20%, 34.07%, 60.67%, 22.83%, 30.33%, 56.91%, 20.75%, 29.16%, 62.64%, and 17.92% and under Loma Prieta earthquake excitations are 58.80%, 56.70%, 61.24%, 64.20%, 57.03%, 60.85%, 61.77%, 55.63, 58.74%, 67.12%, and 60.67% respectively across all stories of controlled building as compared to uncontrolled building. Reduction in acceleration at first, second and third storey in Regular shape building, C shape building, L shape building and T shape building in Y-direction is 56.13%, 51.81%, 55.19%, 66.65%, 51.14%, 56.49%, 51.98%, 48.08%, 53.78%, 56.08%, 50.47% and 57.49% respectively as compared to uncontrolled response under Elcentro excitation.. Reduction in acceleration for Regular shape building, C shape building, L shape building and T shape building under Kobe earthquake excitations are 74.77%, 62.73%, 59.52%, 80.18%, 72.18%, 66.81%, 76.38%, 67.09%, 63.24%, 72.42%, 66.27% and 63.56% under Northridge earthquake excitations are 50.91%, 23.16%, 28.99%, 56.30%, 10.87%, 17.34%, 52.51%, 15.34%, 23.75%, 45.43%, 1.23% and 9.88% and under Loma Prieta earthquake excitations are 59.02%, 55.91%, 58.12%, 64.08%, 59.87%, 61.73%, 60.13%, 57.68%, 59.20%, 54.26%, 55.61% and 56.64% respectively across all stories of controlled building as compared to uncontrolled building. It is evident from results obtained that visco-elastic damper is quite effective in controlling seismic response of asymmetric building under consideration. 290

10 V. CONCLUSION A three storey asymmetric building having Regular shape, C shape, L shape and T shape with visco-elastic damper subjected to four earthquake excitations is considered and designed using E- Tabs software. quantities like displacement, drift and acceleration are extracted. It is concluded that visco-elastic damper is quite effective in controlling the response of asymmetric building having Regular shape, C shape, L shape and T shape under all the earthquake excitations. Reduction in displacement ranges between 46.86% to 85.92%, inter-storey drift ranges between 35.79% to 85.92% and acceleration ranges between 1.23% to 80.18% for asymmetric building with visco-elastic damper under various earthquake excitations. REFERENCES [1] Jinkoo Kim and Sunghyuk Bang "Optimum distribution of added visco-elastic dampers for mitigation of torsional responses of plan-wise asymmetric structures", Engineering Structures 24 (2002), pp [2] L.P.B Madsen, D.P.Thambiratnam and N.J.Perera "Seismic response of building structures with dampers in shear walls", Computers and Structures 81 (2003), pp [3] K.C. Chang, Y.Y. Lin and M.L.Lai "Seismic Analysis and Design of Structures with Viscoelastic Dampers", Proceedings, ISET Journal of Earthquake Technology, Paper No. 380,Vol.35,No.4, December 1998,pp [4] Marcos Garcia, Juan C. de la Llerac and Jose L. Almazan "Torsional balance of plan asymmetric structures with viscoelastic dampers", Engineering Structures 29 (2007), pp [5] T.T Soong and M.C. Constantinou, "Passive and Active Structural Vibration Control in Civil Engineering", March [6] Robert D.Hanson and T.T Soong "Seismic design with supplementary energy dissipation devices", monograph series, EERI, [7] CSI Analysis Reference Manual for E-TABS 2000, Computers and Structures, Inc, Berkeley, California, USA. [8] A.K. Chopra, Dynamics of structures, theory and application to earthquake engineering, Pearson Education Inc., [9] Humar J.L. "Dynamics of structures", Second Edition, [10] Abhijitsinh Parmar, Vidhi Patel, Bhrugu Kotak and Mittal Patel, Seismic Control of Asymmetric Building Using VISCOUS DAMPER. International Journal of Civil Engineering & Technology (IJCIET).Volume: 5,Issue:12,Pages: [11] Evinur Cahya, Toshitaka Yamao and Akira Kasai, Seismic Behavior using Static Pushover Analysis and Dynamic Analysis of Half-Through Steel Arch Bridge under Strong Earthquakes, International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 1, 2014, pp , ISSN Print: , ISSN Online: [12] Dharane Sidramappa Shivashaankar and Patil Raobahdur Yashwant, Design and Practical Limitations in Earthquake Resistant Structures and Feedback, International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 6, 2014, pp , ISSN Print: , ISSN Online: [13] Dharane Sidramappa Shivashaankar and Patil Raobahdur Yashwant, Earthquake Resistant High Rise Buildings New Concept, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 5, Issue 6, 2014, pp , ISSN Print: , ISSN Online:

Seismic Response Control of the Building using Passive Devices

INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD 382 481, 08-10 DECEMBER, 2011 1 Seismic Response Control of the Building using Passive Devices Vijay Chachapara, Sharadkumar Purohit and P. V. Patel