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STABILIZATION OF TALL BUILDING AGAINST THE WIND LOAD

Harsh Naik1* and Vasugi V2

1M. Tech, Structural Engineering, SMBS, VIT University- Chennai Campus, Chennai- 600127, India

2Associate Professor, SMBS, VIT University- Chennai Campus, Chennai- 600127, India

*Corresponding Author:
Harsh Naik
M. Tech, Structural Engineering, SMBS
VIT University- Chennai Campus
Chennai- 600127, India
E-mail: hrnaikgoal92@gmail.com

Received Date: 17 June, 2017 Accepted Date: 22 August, 2017

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Abstract

Due to urbanization, tall building became most suitable option for offices and residential building. Where space is limited, Tall and slender buildings can be utilize. In the present study the wind analysis of G+34 floor was done by Gust Loading Factor approach according to the guideline of IS-456 (Part 3)-1987 and compare the results by analyzing the same model according the guideline of the IITK. G+34 floor building were analyze by Gust Loading Factor to identify the base shear, storey drift and storey shear by using software package ETAB's 15.0.0 version. New advancement require for the calculation of the wind load in India. In this research the comparison of wind load calculation between the old IS-456(Part 3)-1987 code and proposed draft code made, so clear idea can be suggested for the wind analysis of the high rise building in India.

Keywords

Storey displacement, Base shear, Storey drift, Gust loading factor, Wind analysis

Introduction

Day by day development in the vertical cities is increasing in the India as peoples are migrating from the villages to the cities for the easy life and the different purposes. For the accommodation of the more population in less space, high rise building is most suitable option. As the height of the structure increases, impact of the lateral load increases. Generally wind load governing for the structure more than the 100 m height. For the wind analysis of the tall building guideline is given in to the IS-456 (Part 3)-1987. Which majorly includes the effect of the roughness, terrain category, surrounding building, basic wind speed, soil type and importance factor in only along the wind direction. From the previous cyclone and wind data it is observed that when wind occurs, structure not only effected in along the wind direction but also in across the wind direction. Because of this reason, damage observed in so many structures although structure is well design for the wind effect according the IS-456 (Part 3)-1987.

Literature Review

(Chen, 1994) analyzed the response of the structure under the random wind loading and observed the effect of wind in along the wind direction. (Yu, et al., 2012) researched about the effect of the wind on the low rise building and effect of the geometry on the wind loading. (Sygulski, 1996) checked the stability of the structure and find the effect of the damping on the wind calculation. (Chen, et al., 2011) done the wind tunnel test. So many researcher has done work for the dynamic wind analysis. (Solari, 1990) finds the effect of local wind. (Wood, 1983) modified gust factor approach. (Paginini and Piccardo, 2017) checked the gust factor approach by flow dynamic concept. (Deaves, 1993) researched about the effect expouser in the wind loading. For the coastal wind climate (Bardal and Saetran, 2016) analyzed the structure. (Kolchi, et al., 1993; Abohela, et al., 2013) analyzed the different shaped model for the wind loading.

Modeling and Analysis

For the accurate result generally Static and Dynamic analysis is done as per guideline given into the Indian standards. Static analysis can be perform as per guideline mentioned in IS-875 (Part 3)-section 5.3 and dynamic analysis is done by applying the gust factor approach as per guided in section 7. Specific criteria are mention for the condition where dynamic analysis is required. If the maximum lateral dimension to height is less than 5 and /or building natural frequency is less than 1 hz than dynamic analysis is required. For this research work G+34 building is analyzed which has 106 height. The structure has natural frequency less than one. For the study of the proposed guideline of the dynamic analysis in the IITK guideline handbook, analysis of three model is done to compare the result of storey drift. All the parameters of the three model is shown in the Table 1 (Baker and Pawlikowski, 2015; Smethrust and Green; 2012).

Y shape G+34 floor building with 106 m height is taken consider for the all three analysis. Plan view and 3D view is shown in Figures.1 and 2).

icontrolpollution-Plan-view

Figure 1: Plan view of model.

icontrolpollution-model-view

Figure 2: 3D view of model.

Parameters Model 1 Model 2 Model 3
Height (m) 106 106 106
Bottom Storey Height (m) 4 4 4
Storey Height (m) 3 3 3
Soil Type Medium Medium Medium
Terrain Category 3 3 3
Apply Code IS-875  (Part 3) 1987 IS-875
(Part 3) 1987
Proposed Draft IS-875
(Part 3)2015
Type of Analysis Static Dynamic Dynamic
Shape Y Y Y
Thickness of Slab (mm) 125 125 125
Beam Size      
Material properties
Grade of Concrete m25 m25 m25
Grade of Steel Fe 415 Fe 415 Fe 415
Dead load intensities
Floor Finish on floors (kN/m2) 1.75 1.75 1.75
Floor Finish on roof (kN/m2) 2 2 2
Live load intensities
(Kn/m2)
Live load on floors 3 3 3
Live load on roof 1.5 1.5 1.5

Table 1. Parameters of the model

Gust Loading Factor

For the dynamic analysis first of all the gust factor is calculated according to the Indian standards and IITK guideline book. Gust factor is the ratio of the gust wind to mean wind. Gust factor acted like a dynamic factor for the static load and multiplied it with static force on the each floor. For the calculation of the Gust loading factor, guideline is given into the IS - 456 (Part 3)-1987 in section 7. In Table 2 gust loading factor in along the wind direction and across the wind direction is written for the each floor. This load factor is multiplied by area and constant and converted into the static force. The same amount of static force applied to each floor and analysis is done.

Floor As Per IS 456
(Part 3)-1987
As per IITK Guideline
Along the Wind Direction
As per IITK Guideline
Across the wind direction
Gx Gy Gx Gy Gx Gy
GRFL 2.0496 2.0496 2.8887 2.9763 0.0868 0.0456
1 Floor 2.0505 2.0533 3.0118 3.0958 0.1519 0.0798
2 Floor 2.0514 2.0542 3.1047 3.189 0.217 0.114
3 Floor 2.0521 2.0556 3.1853 3.2733 0.2821 0.1482
4 Floor 2.0544 2.0558 3.2561 3.3486 0.3472 0.1823
5 Floor 2.0554 2.0584 3.3204 3.4178 0.4123 0.2165
6 Floor 2.0585 2.0625 3.38 3.4826 0.4774 0.2507
7 Floor 2.0618 2.0671 3.4363 3.5447 0.5425 0.2849
8 Floor 2.0657 2.0885 3.4904 3.605 0.6075 0.3191
9 Floor 2.0702 2.0888 3.5425 3.6641 0.6726 0.3533
10 Floor 2.0707 2.0938 3.5931 3.722 0.7377 0.3875
11 Floor 2.0728 2.1037 3.6426 3.7795 0.8028 0.4217
12 Floor 2.0755 2.1072 3.6911 3.8368 0.8679 0.4558
13 Floor 2.0755 2.1117 3.7389 3.894 0.933 0.49
14 Floor 2.0761 2.1176 3.7859 3.9512 0.9981 0.5242
15 Floor 2.0782 2.1291 3.8323 4.0086 1.0632 0.5584
16 Floor 2.0811 2.1368 3.8779 4.066 1.1283 0.5926
17 Floor 2.0833 2.1416 3.9229 4.1235 1.1934 0.6268
18 Floor 2.0833 2.1463 3.9671 4.1811 1.2585 0.661
19 Floor 2.0854 2.1486 4.0106 4.2388 1.3236 0.6952
20 Floor 2.0862 2.1594 4.0531 4.2965 1.3887 0.7294
21 Floor 2.0884 2.1681 4.0947 4.3539 1.4538 0.7635
22 Floor 2.0885 2.1714 4.135 4.4108 1.5189 0.7977
23 Floor 2.1255 2.1766 4.1741 4.467 1.584 0.8319
24 Floor 2.1278 2.1801 4.2115 4.5219 1.6491 0.8661
25 Floor 2.1343 2.185 4.2473 4.5753 1.7142 0.9003
26 Floor 2.1366 2.2117 4.281 4.6266 1.7792 0.9345
27 Floor 2.1366 2.2167 4.3125 4.6751 1.8443 0.9687
28 Floor 2.1389 2.2359 4.3415 4.7203 1.9094 1.0029
29 Floor 2.1389 2.2533 4.3679 4.7614 1.9745 1.0371
30 Floor 2.1391 2.2646 4.3913 4.7978 2.0396 1.0712
31 Floor 2.1414 2.2731 4.4116 4.8288 2.1047 1.1054
32 Floor 2.1459 2.2831 4.4287 4.8538 2.1698 1.1396
33 Floor 2.148 2.2904 4.4423 4.8723 2.2349 1.1738
34 Floor 2.1482 2.311 4.4525 4.8841 2.3 1.208

Table 2. Gust loading factor

Force calculation

Wind load force on each floor:

F=(Cpe-Cpi)×A×Pz

Where,

Cpe=External pressure coefficient, Cpi=Internal pressure coefficient, A=Surface area of structural or cladding unit, Pz=Design wind pressure Table 3.

Floor   As Per IS 456
(Part 3)-1987
As per IITK Guideline
Along the Wind Direction
As per IITK Guideline
Across the wind direction
Fx (KN) Fy (KN) Fx (KN) Fy (KN) Fx (KN) Fy (KN) Fx (KN) Fy (KN)
GRFL 249.027 174.30 128.50 93.44145 181.116 130.47234 5.4417 1.9983
1 Floor 247.757 173.41 96.419 70.20812 141.623 101.78296 7.1422 2.6228
2 Floor 246.912 172.82 96.463 70.23981 145.994 104.84827 10.203 3.7469
3 Floor 244.807 171.35 108.42 78.97480 168.295 120.92339 14.903 5.473
4 Floor 242.710 169.8 120.31 87.54800 190.694 137.11931 20.332 7.4665
5 Floor 241.039 168.71 130.94 95.36039 211.546 152.24983 26.266 9.6456
6 Floor 238.875 167.20 139.38 101.5542 228.869 164.8830 32.323 11.87
7 Floor 236.887 165.80 146.67 106.932 244.464 176.31781 38.591 14.172
8 Floor 234.906 164.42 154.21 113.3767 260.568 188.17424 45.356 16.656
9 Floor 232.934 163.04 160.99 118.1207 275.488 199.22953 52.309 19.209
10 Floor 230.971 161.66 165.57 121.7367 287.299 208.0861 58.988 21.662
11 Floor 229.015 160.29 170.34 125.7182 299.350 217.17494 65.978 24.229
12 Floor 227.068 158.93 175.24 129.3738 311.657 226.51022 73.283 26.912
13 Floor 225.130 157.57 179.98 133.1615 324.226 236.10423 80.91 29.712
14 Floor 223.199 156.22 184.84 137.0950 337.067 245.96759 88.864 32.634
15 Floor 221.277 154.88 189.90 141.4706 350.181 256.10918 97.153 35.677
16 Floor 219.364 153.54 193.78 144.6820 361.094 264.71877 105.06 38.582
17 Floor 217.458 152.20 196.97 147.2413 370.908 272.59920 112.84 41.437
18 Floor 215.561 150.88 199.98 149.8205 380.826 280.63665 120.81 44.365
19 Floor 213.123 149.17 203.22 152.2599 390.839 288.82747 128.99 47.368
20 Floor 209.608 146.71 206.37 155.329 400.936 297.16446 137.37 50.446
21 Floor 206.123 144.27 209.67 158.2880 411.100 305.63621 145.96 53.6
22 Floor 202.667 141.85 212.79 160.8784 421.313 314.22637 154.76 56.831
23 Floor 199.240 139.45 219.75 163.6349 431.553 322.91289 163.76 60.139
24 Floor 195.842 137.07 223.20 166.2959 441.794 331.66718 172.99 63.526
25 Floor 192.474 134.72 227.14 169.0930 452.007 340.45352 182.43 66.992
26 Floor 187.660 131.35 230.66 173.6214 462.161 349.22857 192.08 70.538
27 Floor 182.181 127.51 233.96 176.5088 472.222 357.94133 201.96 74.165
28 Floor 176.783 123.73 237.54 180.5595 482.155 366.53367 212.06 77.873
29 Floor 170.413 119.28 240.89 184.5328 491.922 374.94169 222.38 81.664
30 Floor 162.102 113.46 244.28 188.0546 501.487 383.09791 232.93 85.537
31 Floor 151.343 105.93 247.95 191.3862 510.816 390.93450 243.7 89.495
32 Floor 139.681 97.769 251.90 194.8825 519.875 398.38717 254.71 93.537
33 Floor 139.681 97.769 254.06 196.9937 525.445 402.94934 264.35 97.076
34 Floor 163.137 114.06 256.01 200.2763 530.644 406.9888 274.11 100.66

Table 3. Force calculation

Result and Discussion

Three models analyzed using Static and Dynamic approach. For the each model, storey drift is taken as an output and compared.

a) The building of Base + 34 Floor (Static analysis as per IS-875 part -3, 1987)

b) The building of Base + 34 Floor (Gust Loading Factor analysis as per IS-875 part -3, 1987)

c) The building of Base + 34 Floor (Gust Loading factor Analysis as per Proposed Draft code and IITK guideline)

For the above three model Storey drift is been taken as an output and compare with each other in the graph for various condition.

In the (Figure. 3) graph clearly shows that storey drift value is higher in draft code compare to IS -875 (Part 3)-1987 and it also vary from the static analysis output. In the draft code both condition is considered, along the wind condition and across the wind condition. In (Figure. 4-6) we can clearly observe the effect of across the wind direction's component.

icontrolpollution-Storey-drift

Figure 3: Storey drift vs. floors graph for along the wind in wind X direction.

icontrolpollution-floors-graph

Figure 4: Storey drift vs. floors graph for along the wind in wind Y direction.

icontrolpollution-floors-direction

Figure 5: Storey drift vs. floors graph for across the wind in wind X direction.

icontrolpollution-across-direction

Figure 6: Storey drift vs. floors graph for across the wind in wind Y direction.

Conclusion

In the present study, three type of model analyzed by ETAB 15.0.0 and storey drift of the all model checked for Gust Loading Factor and compared with each other. From this study, it is concluded that:

1. In all other cases major difference will not come between static and dynamic analysis. But if we observe the (Figure. 3 and 6). In (Figure. 3) dynamic analysis shows higher value, which indicated that for the two condition mentioned in the IS 875 (Part 3)-1987 dynamic analysis is required.

2. In the (Figure. 3-5), we can observe that storey drift value is coming higher when it is calculated by proposed draft guideline. Recent changed view of wind blowing is necessary to be implemented for the accurate analysis for keeping structure safe from the wind loading (Figure. 6).

References

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