IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
WIND ANALYSIS OF SQUARE AND RECTANGULAR GEOMETRY MULTISTORIED BUILDING Bhumika Pashine1, V. D. Vaidya2, Valsson Varghese3, D. P. Singh4 1
Student, M Tech, Structural Engineering, KDK College of Engineering., Maharashtra, India Assistant Professor, Civil Engineering Department, KDK College of Engineering., Maharashtra, India 3 Professor and Head of Civil Engineering Department, KDK College of Engineering., Maharashtra, India 4 Principal and Professor, Civil Engineering Department, KDK College of Engineering., Maharashtra, India 2
Abstract Its today’s trend that we are expanding vertically instead of horizontally and constructing tall structures, either due unavailability of land or due man’s desire to achieve something which unachievable and challenge himself. However whatever be the case as when we increase the height of the structure wind load becomes one of the most predominating factor in the design of any high rise structure, hence it is very important that a structural engineer should understand how the structure will behave as the height increases.In this paper effect of wind on tall structure is studied and analyzed, two geometry, square and rectangular with same plan area were selected. Software models for these two geometries were made in STAAD with three different storeyheightsi.e 15 storey, 25 storey and 30 storey and models were analyzed for both along and across wind condition for various parametric values.
Keywords: Wind analysis, Tall Structure, Square shape geometry, Rectangular shape geometry, Variation in height --------------------------------------------------------------------***---------------------------------------------------------------------1. INTRODUCTION Now a days it has become necessity to construct tall building for offices as well as residential purpose in big cities, to accommodate ever increasing population growth in available amount of space,especially in developing country like India. These building are generally designed for square and rectangular shape cross section.As the height of structures increases it becomes more complex, it is vital that the structural engineers must know theperformanceof the buildingagainst wind pressure in order to create costeffective designs satisfying serviceability requirements,as wind pressure is one of the dominating factors during design of tall buildings. For design of building considering the effect of wind loads, design engineers use values of wind pressure coefficient given in relevant handbooks or standards for wind loads, in India IS: 875 (Part-3) 1987) is used. J. A. Amin and A. K. Ahuja (2008) has done experimental study of wind pressures on irregular plan shape buildings[1], and concluded that changing the plan dimension has subsequent effect on the wind pressure and thus on behavior of structure.Yi Tang and Xin-yang Jin (2009) has done study on equivalent Static Wind Loads of an Asymmetric Building with 3D Coupled Modes[2], and concluded that peak responses obtained by applying Equivalent static wind loading are very close with results calculated by CQC (Complete Quadratic Combination) methods.C.M. Chana, M.F. Huangb, K.C.S. Kwokc (2010) [3], has done Integrated wind load analysis and stiffness optimization of tall buildings with 3D modes and discovered that by stiffness optimization methodwind-induced torsional loads on the building with the irregular plan have been
significantly reduced.Yi Hui n, Yukio Tamura, Akihito Yoshida (2012) [4], has studied the effect of mutaul interference between two tall building models with different geometry on local peak pressure coefficients and found thatthe effect of peak coefficient greatly depend on building shapes and wind directions.Rachel Bashor,Sarah Bobby , Tracy Kijewski-Correa, Ahsan Kareem (2012) [5] studied full-scale performance evaluation of high rise buildings under wind pressure.Michael Jesson, Mark Sterling , Chris Letchford, Chris Baker, (2015),[6] studied about aerodynamic forces due to transient windson the roofs of low-, mid- and high-rise buildings and concluded that pressure coefficients are of greatest magnitude when the roof is above the region of maximum outflow velocity.
2. PROBLEM STATEMENT This paper is an attempt to study behavior of the tall buildings under wind load and to evaluate analytical techniques to compute dynamic response and present a detailed comparison for two different plan geometry with three storey heights i.e. 15, 25, 30 storeyalong and across wind direction.
Fig -1: Along and Across Wind Response
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IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
2.1 Geometry of building:
Type of building : Commercial Plinth area : 900 sq. mt. Floor Height : 3.5m Depth of foundation : 2.0 m
Fig -4:Typical3-D model for Rectangular geometry (ModelM1)
3. RESULTS AND DISCUSSION Fig -2: Square plan (Model-M1) aspect ratio 1 and rectangular plan (Model-M2) aspect ratio 2.25
2.2 Wind Data
As per IS 875-Part III Basic Wind Speed of Nagpur: 44 m/s Terrain Category: III
2.3 Software Modeling
3.1 Variation in Parametric Values Due To Change in Geometry 3.1.1 For 15 Storey Structure
15 Storey Models M1 WL across length
40.75
79.30
79.30
100.63
Computer modeling of the building is performed using the finite element software STAAD-Pro. R.C Buildings of different storey are modeled as beam-column building composed of columns, beams as shown in Figure 3& 4. The columns are assumed to be fixed at their base. A detailed three-dimensional model is employed for wind analysis.
Variation in various parameter such as maximum displacement, storey drift, axial force, shear force, bending moment and torsional moment is worked out after performing analysis. The results are compared in two categories, (i) variation in parametric values due to change in geometry (from chart 1 to 18), (ii) variation in parametric values per unit length due to change in height (from chart 19 to 27).
M1 WL along length
M2 WL across length
Top Displacements (mm)
M2 WL along length
Chart -1: Variation of maximum displacement in model M1 and M2, 15 storey for wind load along and across length Fig -3: Typical3-D model for Square geometry (Model-M1)
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IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
4.20
75.39
75.39
M1 WL along length
88.73
115.90
15 Storey Models M1 WL across length
8.16
8.16
10.27
15 Storey Models
M2 WL along length
M2 WL along length
Storey Drift(mm)
Shear Force(kN)
Chart -2: Variation of Storey drift in model M1 and M2, 15 storey for wind load along and across length
Chart -5: Variation of Shear Force in model M1 and M2, 15 storey for wind load along and across length
3.55
M1 WL along length 1.29
5075.46
M1 WL along length M2 WL across length
Axial Force(kN) Chart -3: Variation of Axial Force in model M1 and M2, 15 storey for wind load along and across length
M1 WL across length
2.83
M1 WL across length
M2 WL along length
Torsional Moment (kN-m)
M2 WL across length M2 WL along length
Chart -6: Variation of Torsional Moment in model M1 and M2, 15 storey for wind load along and across length
3.1.2 For25 Storey Structure
328.67
15 Storey Models
348.15
25 Storey Models M1 WL across length
136.45
M2 WL across length
219.00
M1 WL along length
219.00
M1 WL across length 140.83
271.89
15 Storey Models 2.83
5296.52
5296.50
15 Storey Models
5075.46
M1 WL along length M2 WL across length
M2 WL across length
271.02
M1 WL across length
M2 WL along length Bending Moment (kN-m) Chart -4: Variation of Bending Moment in model M1 and M2, 15 storey for wind load along and across length
Top Displacements (mm)
M1 WL along length M2 WL across length M2 WL along length
Chart -7: Variation of maximum displacement in model M1 and M2, 25 storey for wind load along and across length
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IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
8.46 Storey Drift(mm)
109.68
M1 WL along length
M2 WL across length
M2 WL across length
M2 WL along length
M2 WL along length Shear Force(kN) Chart -11: Variation of Shear Force in model M1 and M2, 25 storey for wind load along and across length
14.61
25 Storey Models
M1 WL along length 5.02
10016.05
M1 WL along length M2 WL across length M2 WL along length
M1 WL across length
8.95
M1 WL across length 8.95
10221.33
25 Storey Models 10221.28
M1 WL across length
M1 WL along length
Chart -8: Variation of Storey Drift in model M1 and M2, 25 storey for wind load along and across length
10016.05
173.96
132.23
132.23
25 Storey Models M1 WL across length
13.50
13.50
21.17
25 Storey Models
Torsional Moment (kN-m)
M2 WL across length M2 WL along length
Axial Force(kN) Chart -9: Variation of Axial Force in model M1 and M2, 25 storey for wind load along and across length
3.1.3 For30Storey Structure
30 Storey Models M1 WL across length
194.96
491.32
M2 WL across length
308.70
M1 WL along length
308.70
M1 WL across length 632.72
974.98
1486.26
25 Storey Models
974.98
Chart -12: Variation of Torsional Moment in model M1 and M2, 25 storey for wind load along and across length
M2 WL along length Bending Moment (kN-m) Chart -10: Variation of Bending Moment in model M1 and M2, 25 storey for wind load along and across length
Top Displacements (mm)
M1 WL along length M2 WL across length M2 WL along length
Chart -13: Variation of maximum displacement in model M1 and M2, 30 storey for wind load along and across length
_______________________________________________________________________________________ Volume: 05 Issue: 06 | Jun-2016, Available @ http://ijret.esatjournals.org
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IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
30 Storey Models
M2 WL across length
229.72
294.24
M1 WL along length
141.45
9.77
M1 WL across length
141.45
M1 WL across length
15.51
15.51
24.29
30 Storey Models
M1 WL along length M2 WL across length
M2 WL along length
M2 WL along length
Storey Drift(mm) Shear Force(kN) Chart -14: Variation of Storey Drift in model M1 and M2, 30 storey for wind load along and across length
Chart -17: Variation of Shear force in model M1 and M2, 30 storey for wind load along and across length
25.56
M1 WL across length
8.62
M2 WL across length
M1 WL along length
15.64
15.64
27008.09
30 Storey Models
M1 WL across length M1 WL along length
13660.24
13660.24
27008.01
30 Storey Models
M2 WL along length
Chart -15: Variation of Axial force in model M1 and M2, 30 storey for wind load along and across length
2583.56
30 Storey Models M1 WL across length 1098.86
1700.37
M2 WL along length Torsional Moment (kN-m)
Axial Force(kN)
1700.37
M2 WL across length
M1 WL along length M2 WL across length M2 WL along length
Chart -18: Variation of Torsional moment in model M1 and M2, 30 storey for wind load along and across length From chart 1 to 18 , it can be seen that in case of square geometry direction of wind does not affect the behavior of structure at any height as stiffness is same in both direction whereas in case of rectangular geometry parametric values are considerably more if wind pressure is acting across the length of the structure then wind direction along the length as stiffness of building is more when wind acts along the length.
3.2 Variation In Parametric Values Per Unit Length Due To Change In Height In this case comparative study is done in the form of chart for same geometry but different building height for various parametric characteristics.
Bending Moment (kN-m) Chart -16: Variation of Bending moment in model M1 and M2, 30 storey for wind load along and across length
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IJRET: International Journal of Research in Engineering and Technology
4.00 M1 Wind Direction across Length
2.00 1.00 0.00 15
25
30
Axial Fore per meter length in KN
Chart -19: Variation in Displacement per unit height in model M1 VS No. of storey
Variation in Axial Force per unit height VS Number of Storey (Square Geometry) 150.00 M1 Wind Direction across Length
50.00 0.00 15
25
30
Number of Storey
M1 Wind Direction along Length
Bending Moment per meter length in KN m
Chart -20: Variation in Axial Force per unit height in model M1 VS No. of storey
Variation in Bending Moment per unit height VS Number of Storey (Square Geometry) 20.00 M1 Wind Direction across Length
10.00 0.00 15
25
30
Number of Storey
0.20
M1 Wind Direction across Length
0.10 0.00 15
25
30
Number of Storey
M1 Wind Direction along Length
Chart -22: Variation in Torsional Moment per unit height in model M1 VS No. of storey
Number of Storey
100.00
Variation in Torsional Moment per unit height VS Number of Storey (Square Geometry)
M1 Wind Direction along Length
M1 Wind Direction along Length
Chart -21: Variation in Bending Moment per unit height in model M1 VS No. of storey
3.2.2 ForRectangular Geometry Top Displacement per meter length in mm
3.00
Variation in Displacement per unit height VS Number of Storey (Rectangle Geometry) 30.00 M2 Wind Direction across Length
20.00 10.00 0.00 15
25
30
M2 Wind Direction along Length
Number of Storey Chart -23: Variation in Displacement per unit height in model M2 VS No. of storey
Axial Fore per meter length in KN
Top Displacement per meter length in mm
Variation in Displacement per unit height VS Number of Storey (Square Geometry)
Torsional Moment per meter length in KN m
3.2.1 ForSquare Geometry
eISSN: 2319-1163 | pISSN: 2321-7308
Variation in Axial Force per unit length VS height of Storey (Rectangle Geometry) 300.00 M2 Wind Direction across Length
200.00 100.00 0.00 15
25
30
Number of Storey
M2 Wind Direction along Length
Chart -24: Variation in Axial Force per unit height in model M2 VS No. of storey
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IJRET: International Journal of Research in Engineering and Technology
Bending Moment per meter length in KN m
Variation in Bending Moment per unit height VS Number of Storey (Rectangle Geometry)
5. 30.00 M2 Wind Direction across Length
20.00 10.00 0.00 15
25
30
M2 Wind Direction along Length
Number of Storey Chart -25: Variation in Bending Moment per unit height in model M2 VS No. of storey
Torsional Moment per meter length in KN m
4.
Variation in Torsional Moment per unit height VS Number of Storey (Rectangle Geometry) 0.30 M2 Wind Direction across Length
0.20 0.10 0.00 15
25
30
M2 Wind Direction along Length
Number of Storey Chart -26: Variation in Bending Moment per unit height in model M2 VS No. of storey From above charts (chart 19 to 26) it can be observed that maximum displacement, axial force, bending moment and torsional moment increases per unit length increases with increase in number of storey for both square and rectangular geometry whereas fluctuation is observer in case of shear force.
4. CONCLUSION The following conclusions are drawn from the study: 1. The geometry of building plays an important role in controlling various parametric coefficients. 2. The square geometry is the most cost effective and serviceable among square and rectangular geometry. 3. If the placement of structure is such that wind direction is along the length of geometry, then the structure behaves better in case of rectangular geometry than that of square geometry.
6.
eISSN: 2319-1163 | pISSN: 2321-7308
Top displacement, storey drift, axial force , shear force, bending moment and torsional moment increases 48%, 46%, 3%, 46%, 40% and 50% respectively in rectangle plan for critical load combination 1.5(DL+LL+WLX) with respect to square geometry when wind load is acting across the length. Top displacement, storey drift, bending moment and torsional moment decreases 40%, 40%, 40%, and 48% respectively in rectangle plan for critical load combination 1.5(DL+LL+WLZ) with respect to square geometry when wind load is acting along the length. All the parametric coefficient increases per unit height.
REFERENCES [1] J. A. Amin and A. K. Ahuja (2008), “Experimental study of wind pressures on irregular plan shape buildings”. BBAA VI International Colloquium on: Bluff Bodies Aerodynamics & Applications Milano, Italy. [2] Yi Tang and Xin-yang Jin (2009), “Equivalent Static Wind Loads of an Asymmetric Building with 3D Coupled Modes”. The Seventh Asia-Pacific Conference on Wind Engineering, Taipei, Taiwan. [3] C.M. Chana, M.F. Huangb, K.C.S. Kwokc (2010), “Integrated wind load analysis and stiffness optimization of tall buildings with 3D modes”. Engineering Structures 32 (2010) 12521261, Elsevier. [4] Yi Hui n, Yukio Tamura, Akihito Yoshida (2012) , “Mutual interference effects between two high-rise building models with different shapes on local peak pressure coefficients”. J. Wind Eng. Ind. Aerodyn. 104–106 (2012) 98–108, Elsevier. [5] Rachel Bashor,Sarah Bobby , Tracy Kijewski-Correa, Ahsan Kareem (2012) , “Full-scale performance evaluation of tall buildings under wind”. J. Wind Eng. Ind. Aerodyn. 104–106 (2012) 88–97, Elsevier [6] Michael Jesson, Mark Sterling , Chris Letchford, Chris Baker, (2015) “Aerodynamic forces on the roofs of low-, mid- and high-rise buildings subject to transient winds”. J. WindEng.Ind.Aerodyn.143(2015)42–49, Elsevier. [7] Mohamed Elsharawy , Khaled Galal, Ted Stathopoulos, (2015) “Torsional and shear wind loads on flat-roofed buildings”. Engineering Structures 84 (2015) 313–324, Elsevier [8] Indian standard codes, IS 875: part 2,3,5- 1987,“Code of practice for Design loads (other than earthquake) for buildings and structures.” [9] Indian standard code, IS 456: 2000, “Indian Standard code of practice for general structural use of plain and reinforced concrete.”
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