Storey Response of G+40 Horizontally Connected Buildings with Dampers

Storey Response of G+40 Horizontally Connected Buildings with Dampers

Mayuri M. Baviskar

Department of Civil Engineering MGMs Jawaharlal Nehru Engineering College

Aurangabad, Maharashtra, India

Prof. L. G. Kalurkar

Department of Civil Engineering MGMs Jawaharlal Nehru Engineering College

Aurangabad, Maharashtra, India

Abstract Analyzing the response of structure to ground shaking caused by an earthquake is one the most important application of structural dynamics. Tall structures are more exposed to dynamic loads, earthquake and wind effects. Tall buildings are characterized by low natural frequency. Hence, they can vibrate significantly under lateral dynamic earthquake loads. This paper deals with the analysis of G+40 storey buildings connected horizontally with the truss bridge at 21st and 31st storey having fixed base and shows the storey response curves of buildings connected with dampers and without dampers. The building frame type used is ordinary moment resisting frame (OMRF). The dampers used are fluid viscous dampers (FVD) having force capacity of 500KN. The analysis is done using ETABS V16 software.

Keywords Dampers, fluid viscous damper, storey response curve, fixed base, seismic response, ordinary moment resisting frame, ETABS V16.

structure can all collapse or part collapse or wont collapse throughout or after earthquake, time history analysis is required to perform. The results obtained from analysis are studied to know the actual behavior of structure.

I.INTRODUCTION

As the business activities demands to be on the point of one another and at the town centre, tall buildings get a lot of attention in todays life. Also, because they form distinctive landmark, tall buildings are oftentimes developed in town centers as status image for company organization. Due to the speedy increase in population and reduction in accessibility of land, vertical accommodation is obtaining a lot of preference which is resulting in vertical town development. The higher land costs, reduction in urban sprawl and for agricultural production, residential buildings are growing upward. Buildings are designed primarily to serve the needs of occupancy whether residential or commercial. At the same time, clients requirement regarding aesthetic qualities plays important role.

The modeling of high rise structure for analysis is depends on the approach of research. The bottom shaking that occurs in an earthquake are often represented as a series of multidirectional random acceleration pulses. The seismal response of tall building will depend on the dynamic properties of the structure, ground motion at the foundation and mode of soil structure interaction. Response spectrometry shows that how the structure will respond if damping is elicited. Various curves are developed with different levels of damping. As damping increases, response spectra shift downward. As per typical earthquake resistant design, structure is designed for forces which are much less than the actual design earthquake forces. Therefore, throughout earthquake event, structure undergoes severe non resilient deformation with non repairable damages. RCC structure can be made ductile with the help of reinforcing steel. Thus, to grasp whether or not the

Fig 1: Real horizontally connected structures.

1. EXAMPLE BUILDING

   Building set up chosen for this project is as shown in figure below. Two buildings are connected by a truss bridge of 50m length at twenty first floor and thirty first floor. The structure is built with ordinary moment resisting frame (OMRF). Both buildings are symmetric to each other and considered to be served as residential building. Building is having forty storeys for accommodation purpose and top story as terrace. The columns are fixed at base. Two column sizes are utilized in

   structure. Column of size 0.85m x 0.65m are used up to 10th storey and 0.75m x 0.55m are used for rest of the storey. Beams having cross sectional size 0.3m x 0.6m. The floor to floor height is kept constant as 3m and slab thickness as 0.18m throughout the structure. 4 lifts are provided at each floor per building. Shear wall of 0.3m thick are used for the lift sections. Concrete grades used are M35 and M40 while steel used is of grade HYSD500. Instead of traditional brick wall Autoclave Aerated Concrete (AAC) Blocks are used as wall having unit weight ranging from 4.6 kN/m3 to 7.5 kN/m3 which is almost 1/3rd of normal concrete. Building is analyzed for all zones for earthquake. Load combinations are taken as per IS 456:2000 and earthquake loading is taken as per IS 1893:2002. Load combinations used are listed below: 1.5(DL+LL)

   1.5(DL±EQx)

   1.5(DL±EQy)

   1.5(DL±WLx)

   1.5(DL+±WLy)

   1.2(DL+LL±EQx)

   1.2(DL+LL±EQy)

   1.2(DL+LL±WLx)

   1.2(DL+LL±WLy)

   0.9DL±1.5EQx

   0.9DL±1.5EQy

   Fig 2: 3-D view of G+40 building.

   1. Fluid Viscous Dampers:

      The fluid viscous dampers are hydraulic devices that dissipate the mechanical energy of seismal events and cushion the

      impact between structures. Theyre versatile and might be designed to permit free movement in addition as controlled damping of a structure to safeguard from wind load, thermal motion or seismic events. The fluid viscous damper is consisting of oil cylinder, piston, piston rod, lining, medium, pin head and other main parts. The piston may create mutual motion within the oil cylinder. The piston is provided with damping structure and therefore the oil cylinder is jam-packed

      with fluid damping medium. Once the external stimulation (such as earthquake, wind vibration) reaches to the engineering structure, itll be deformed and drive the damper to move, which will occur the pressure difference on the different side of the piston. Then the medium can undergo the damping structure and make damping power, which will occur the exchange of power (the mechanical power exchange to heat power). All which will reach the aim of reducing the engineering structures vibration.

      Fig 3: schematic diagram of Fluid Viscous Damper

      Damper system are designed and made to safeguard structural integrities, management and stop structural damages by fascinating seismic energy and reduces deformations within the structure. Due to easy installation, adaptability, coordination with other members and variety in their sizes, viscous dampers have several applications in planning and retrofitting..

      In this project, each building is connected with 6 fluid viscous dampers at alternate floors. Dampers having capacity of 500kN are used. Table showing damper capacity is shown below:

      TABLE 1: FVD WITH DIFFERENT CAPACITIES FORCES (KN)

      Force (kN)	Spherical Bearing Bore Diameter (mm)	Stroke (mm)	Clevis Thickness (mm)	Weight (kg)
      250	38.10	±75	43	44
      500	50.80	±100	55	98
      750	57.15	±100	59	168
      1000	69.85	±100	71	254
      1500	76.20	±100	77	306
      2000	88.90	±125	91	500
      3000	101.60	±125	117	800
      4000	127.00	±125	142	1088
      6500	152.40	±125	154	1930

   2. Response Spectrum Analysis:

      Response spectra are curves plotted between maximum response of system subjected to specified earthquake ground motion and its time period (or frequency). Response spectrum can be interpreted as the locus of maximum response of a system for given damping ratio. Response spectra thus helps in obtaining the peak structural responses under linear range, which can be used for obtaining lateral forces developed in structure due to earthquake thus facilitates in earthquake-

      25th floor	41.141	50.107
      24th floor	39.152	47.836
      23rd floor	37.285	45.539
      22ndfloor	35.258	43.221
      21st floor	33.373	40.888
      20th floor	31.328	38.545
      19th floor	29.446	36.199
      18th floor	27.405	33.859
      17th floor	25.545	31.533
      16th floor	23.534	29.226
      15th floor	21.718	26.941
      14th floor	19.75	24.68
      13th floor	17.997	22.449
      12th floor	16.093	20.254
      11th floor	14.426	18.102
      10th floor	12.608	15.998
      9th floor	11.054	13.951
      8th floor	9.348	11.968
      7th floor	7.94	10.059
      6th floor	6.377	8.236
      5th floor	5.17	6.511
      4th floor	3.793	4.901
      3rd floor	2.82	3.479
      2nd floor	1.743	2.203
      1st floor	1.067	1.13
      PL	0.298	0.343
      GL	0.105	0.044
      Base	0	0

      25th floor	41.141	50.107
      24th floor	39.152	47.836
      23rd floor	37.285	45.539
      22ndfloor	35.258	43.221
      21st floor	33.373	40.888
      20th floor	31.328	38.545
      19th floor	29.446	36.199
      18th floor	27.405	33.859
      17th floor	25.545	31.533
      16th floor	23.534	29.226
      15th floor	21.718	26.941
      14th floor	19.75	24.68
      13th floor	17.997	22.449
      12th floor	16.093	20.254
      11th floor	14.426	18.102
      10th floor	12.608	15.998
      9th floor	11.054	13.951
      8th floor	9.348	11.968
      7th floor	7.94	10.059
      6th floor	6.377	8.236
      5th floor	5.17	6.511
      4th floor	3.793	4.901
      3rd floor	2.82	3.479
      2nd floor	1.743	2.203
      1st floor	1.067	1.13
      PL	0.298	0.343
      GL	0.105	0.044
      Base	0	0

      resistant design of structures. The three spectra i.e. displacement, pseudo velocity and pseudo acceleration provide the same information on the structural response. However, each one of them provides a physically meaningful quantity and therefore, all three spectra are useful in understanding the nature of an earthquake and its influence on the design. A combined plot showing all three of the spectral quantities is possible because of the relationship that exists between these three quantities.

   3. Time History Analysis:

      The actual method of mixing the various modal contributions is a probabilistic averaging technique and in some cases, results will not represent the actual behaviour of structure. Time history analysis overcomes this. However, it needs massive procedure efforts. The tactic consists of a step by step direct integration in which the time domain is discretized into a number of tiny increments and for every quantity the equation of motion is solved with the displacements and velocities of the previous step serving as initial functions. The tactic is applicable to both elastic and inelastic analyses. In elastic analysis, the stiffness characteristics of structure are assumed to be constant for whole duration of the earthquake. In inelastic analysis, the stiffness is assumed to be constant through the progressive time solely.

      The proposed building in Zone V with site condition III is analysed for both response spectrum and time history analysis with time history data of El-Centro earthquake in 1940. The analysis is done for with damper condition and without damper condition also. 5% damping is allowed in the structure. The graphs of Spectral Displacement Vs Period, Pseudo Spectral Velocity Vs Period and Pseudo Spectral Acceleration Vs Period are obtained which are shown in result section.

2. RESULTS

   The proposed building in analyzed in different zones of earthquake and the displacement value of each storey are tabulated for with damper and without damper condition for each zone. Chart 1 shows the displacement values of building in Zone II with site type I. Chart 2 shows the displacement values of building in Zone III with site type III. Chart 3 shows the displacement values for Zone IV with site type II and chart 4 shows displacement values for Zone V with site type III.

   Storey	With Damper	Without Damper
   top	66.266	79.234
   40th floor	65.392	77.96
   39th floor	64.115	76.563
   38th floor	62.787	75.087
   37th floor	61.397	73.549
   36th floor	59.954	71.944
   35th floor	58.478	70.269
   34th floor	56.919	68.524
   33rd floor	55.357	66.709
   32ndfloor	53.686	64.828
   31st floor	52.042	62.884
   30th floor	50.269	60.88
   29th floor	48.551	58.82
   28th floor	46.69	56.707
   27th floor	44.907	54.548
   26th floor	42.974	52.346

   Storey	With Damper	Without Damper
   top	66.266	79.234
   40th floor	65.392	77.96
   39th floor	64.115	76.563
   38th floor	62.787	75.087
   37th floor	61.397	73.549
   36th floor	59.954	71.944
   35th floor	58.478	70.269
   34th floor	56.919	68.524
   33rd floor	55.357	66.709
   32ndfloor	53.686	64.828
   31st floor	52.042	62.884
   30th floor	50.269	60.88
   29th floor	48.551	58.82
   28th floor	46.69	56.707
   27th floor	44.907	54.548
   26th floor	42.974	52.346

   TABLE 2: STOREY DISPLACEMENT IN ZONE II (X-DIRECTION)

   Chart -1(a): Comparison of storey displacement in Zone II (x-direction)

   Storey	With Damper	Without Damper
   top	144.194	172.414
   40th floor	142.293	169.641
   39th floor	139.513	166.601
   38th floor	136.626	163.389
   37th floor	133.599	160.042
   36th floor	130.46	156.549

   Storey	With Damper	Without Damper
   top	144.194	172.414
   40th floor	142.293	169.641
   39th floor	139.513	166.601
   38th floor	136.626	163.389
   37th floor	133.599	160.042
   36th floor	130.46	156.549

   Chart -1(b): Comparison of storey displacement in Zone II (y-direction) TABLE 3: STORY DISPLACEMENT IN ZONE III (X-DIRECTION)

   35th floor	127.249	152.905
   34th floor	123.855	149.107
   33rd floor	120.457	145.16
   32ndfloor	116.821	141.066
   31st floor	113.243	136.835
   30th floor	109.386	132.474
   29th floor	105.647	127.992
   28th floor	101.597	123.395
   27th floor	97.719	118.696
   26th floor	93.511	113.905
   25th floor	89.523	109.033
   24th floor	85.194	104.092
   23rd floor	81.131	99.093
   22ndfloor	76.721	94.049
   21st floor	72.62	88.971
   20th floor	68.17	83.873
   19th floor	64.074	78.769
   18th floor	59.632	73.677
   17th floor	55.587	68.616
   16th floor	51.21	63.597
   15th floor	47.258	58.623
   14th floor	42.975	53.703
   13th floor	39.162	48.849
   12th floor	35.018	44.073
   11th floor	31.392	39.39
   10th floor	27.435	34.812
   9th floor	24.054	30.357
   8th floor	20.34	26.042
   7th floor	17.277	21.888
   6th floor	13.876	17.921
   5th floor	11.25	14.168
   4th floor	8.254	10.665
   3rd floor	6.136	7.57
   2nd floor	3.793	4.793
   1st floor	2.321	2.459
   PL	0.648	0.746
   GL	0.229	0.096
   Base	0	0

   Chart 2(a): Comparison of story displacement in Zone III (x-direction)

   Chart 2(b): Comparison of storey displacement in Zone III (y-direction)

   TABLE 4: STOREY DISPLACEMENT IN ZONE IV (X-DIRECTION)

   Storey	With Damper	Without Damper
   top	265.593	317.571
   40th floor	262.092	312.463
   39th floor	256.971	306.865
   38th floor	251.652	300.949
   37th floor	246.078	294.783
   36th floor	240.296	288.35
   35th floor	234.381	281.637
   34th floor	228.131	274.643
   33rd floor	221.872	267.371
   32ndfloor	215.173	259.832
   31st floor	208.584	252.038
   30th floor	201.48	244.005
   29th floor	194.592	235.75
   28th floor	187.133	227.283
   27th floor	179.989	218.627
   26th floor	172.239	209.802
   25th floor	164.894	200.829
   24th floor	156.92	191.728
   23rd floor	149.437	182.521
   22ndfloor	141.313	173.23
   21st floor	133.761	163.877
   20th floor	125.564	154.487
   19th floor	118.019	145.086
   18th floor	109.838	135.706
   17th floor	102.386	126.384
   16th floor	94.324	117.14
   15th floor	87.046	107.978
   14th floor	79.156	98.916
   13th floor	72.133	89.976
   12th floor	64.499	81.179
   11th floor	57.821	72.552
   10th floor	50.532	64.121
   9th floor	44.306	55.915
   8th floor	37.465	47.967
   7th floor	31.823	40.316
   6th floor	25.559	33.008
   5th floor	20.721	26.096
   4th floor	15.204	19.644
   3rd floor	11.302	13.943
   2nd floor	6.987	8.828
   1st floor	4.275	4.529
   PL	1.193	1.374
   GL	0.422	0.176
   Base	0	0

   Chart 3(a): Comparison of storey displacement in Zone IV (x-direction)

   Storey	With Damper	Without Damper
   top	430.305	524.387
   40th floor	424.678	516.047
   39th floor	416.464	506.927
   38th floor	407.940	497.3
   37th floor	399.004	487.273
   36th floor	389.745	476.814
   35th floor	380.265	465.902
   34th floor	370.256	454.533
   33rd floor	360.223	442.712
   32ndfloor	349.494	430.453
   31st floor	338.926	417.775
   30th floor	327.539	404.701
   29th floor	316.483	391.258
   28th floor	304.514	377.458
   27th floor	293.033	363.339
   26th floor	280.580	348.931
   25th floor	268.760	334.265
   24th floor	255.925	319.373
   23rd floor	243.863	304.289
   22ndfloor	230.761	289.049
   21st floor	218.566	273.687
   20th floor	205.320	258.241
   19th floor	193.112	242.758
   18th floor	179.861	227.285
   17th floor	167.779	211.885
   16th floor	154.689	196.588
   15th floor	142.863	181.403
   14th floor	130.021	166.357
   13th floor	118.580	151.486
   12th floor	106.121	136.829
   11th floor	95.215	122.426
   10th floor	83.285	108.324
   9th floor	73.092	94.57
   8th floor	61.861	81.223
   7th floor	52.589	68.349
   6th floor	42.272	56.027
   5th floor	34.310	44.347
   4th floor	25.189	33.421
   3rd floor	18.756	23.749
   2nd floor	11.610	15.054
   1st floor	7.116	7.732
   PL	1.988	2.344
   GL	0.703	0.301
   Base	0	0

   Storey	With Damper	Without Damper
   top	430.305	524.387
   40th floor	424.678	516.047
   39th floor	416.464	506.927
   38th floor	407.940	497.3
   37th floor	399.004	487.273
   36th floor	389.745	476.814
   35th floor	380.265	465.902
   34th floor	370.256	454.533
   33rd floor	360.223	442.712
   32ndfloor	349.494	430.453
   31st floor	338.926	417.775
   30th floor	327.539	404.701
   29th floor	316.483	391.258
   28th floor	304.514	377.458
   27th floor	293.033	363.339
   26th floor	280.580	348.931
   25th floor	268.760	334.265
   24th floor	255.925	319.373
   23rd floor	243.863	304.289
   22ndfloor	230.761	289.049
   21st floor	218.566	273.687
   20th floor	205.320	258.241
   19th floor	193.112	242.758
   18th floor	179.861	227.285
   17th floor	167.779	211.885
   16th floor	154.689	196.588
   15th floor	142.863	181.403
   14th floor	130.021	166.357
   13th floor	118.580	151.486
   12th floor	106.121	136.829
   11th floor	95.215	122.426
   10th floor	83.285	108.324
   9th floor	73.092	94.57
   8th floor	61.861	81.223
   7th floor	52.589	68.349
   6th floor	42.272	56.027
   5th floor	34.310	44.347
   4th floor	25.189	33.421
   3rd floor	18.756	23.749
   2nd floor	11.610	15.054
   1st floor	7.116	7.732
   PL	1.988	2.344
   GL	0.703	0.301
   Base	0	0

   Chart 3(b): Comparison of storey displacement in Zone IV (y-direction) TABLE 5: STOREY DISPLACEMENT IN ZONE V (X-DIRECTION)

   Chart 4(a): Comparison of storey displacement in Zone V (x-direction)

   Chart 4(b): Comparison of storey displacement in Zone V (y-direction)

   TABLE 6: COMPARISON OF MAXIMUM DISPLACEMENTS OF BUILDING (X-DIRECTION)

   ZONE	II	III	IV	V
   with damper	66.266	144.195	267.07	430.3
   without damper	79.234	172.41	317.57	524.387

   Chart 5(a): Comparison of maximum displacements of building (x-direction)

   TABLE 7: COMPARISON OF MAXIMUM DISPLACEMENTS OF BUILDING (Y-DIRECTION)

   ZONE	II	III	IV	V
   with damper	66.636	145	265.59	434.029
   without damper	90.069	195.96	360.99	601.809

   Chart 5(b): Comparison of maximum displacements of building (y-direction)

   Building in Zone V is again analysed for time history analysis with time history data of El-Centro earthquake in order to compare the difference in spectral acceleration, spectral velocity and spectral displacement of building for with damper and without damper condition. The obtained response spectrum curves having 5% damping are shown below. Table 7 summarizes maximum and minimum values of acceleration, velocity and displacement at 0% damping and 0.1% damping.

   Characteristics	With damper		Without damper
   Pseudo spectral Acceleration (mm/sec²)	0% damping	0.10% damping	0% damping	0.10% damping
   	4060.08	440.9	7206.58	497.55
   Pseudo spectral velocity (mm/sec)	1092.26	2.35	1485	2.5
   Spectral displacement(mm)	968.5	0.011	1492.238	0.012

   Characteristics	With damper		Without damper
   Pseudo spectral Acceleration (mm/sec²)	0% damping	0.10% damping	0% damping	0.10% damping
   	4060.08	440.9	7206.58	497.55
   Pseudo spectral velocity (mm/sec)	1092.26	2.35	1485	2.5
   Spectral displacement(mm)	968.5	0.011	1492.238	0.012

   TABLE 8: MAXIMUM AND MINIMUM VALUES OF RESPONSE SPECTRUM CHARACTERISTICS

   Fig 4(b): PSA Vs Time period (without damper condition)

3. CONCLUSION

   From Table 6 and Table 7 it is observed that by providing dampers overall displacement of building in each zone is considerably reduced. Percentage reduction in displacement for Zone II, Zone III and Zone IV is approximately 16% whereas for Zone V it is approximately 18% for x-direction. On other hand, for y-direction percentage reduction in displacement for Zone II, Zone III and Zone IV is approximately 26% and for Zone V is approximately 28%. From Table 7 it is observed that although having 5% damping in the building, the response spectrum characteristics such as pseudo spectral acceleration, pseudo spectral velocity and spectral displacement are much reduced after the application of dampers in the building. For 0% damping, pseudo spectral acceleration is reduced by approximately 44% while for 0.1% damping it is reduced by approximately 11%. It may be possible to increase the percentage reduction in displacement by increasing the capacity of fluid viscous dampers and the dampers are found to be very effective in reducing earthquake responses.

   Fig 4(a): PSA Vs Time period (with damper condition)

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