Comparative of High Rise Building with Same Height and Floor Area Having Different Shape Against Wind Load Analysis using Is 875 (Part-3)

Comparative of High Rise Building with Same Height and Floor Area Having Different Shape Against Wind Load Analysis using Is 875 (Part-3)

Faiz Ahmed

M.Tech Scholar, Dept. of Civil Engineering, BIT Sindri, Dhanbad, Jharkhand, India

Dr. Jitu Kujur

Associate Professor, Dept. of Civil Engineering, BIT Sindri,, Dhanbad, Jharkhand, India

Navin Kumar

M.Tech Scholar Dept. of Civil Engineering, BIT Sindri, Dhanbad, Jharkhand, India

Abstract- The present study investigates the influence of building plan configuration on the wind-induced structural behaviour of high-rise reinforced concrete buildings. Three G+12 building models having square, rectangular, and circular plan configurations are comparatively analysed while maintaining the same building height and floor area. The study aims to evaluate the effect of plan geometry on important structural response parameters under wind loading. Wind loads are determined in accordance with IS 875 (Part 3):2015, considering the relevant wind speed, terrain, topography, and structural parameters. The structural models are analysed using STAAD/ETABS under identical structural, loading, and support conditions. The comparative assessment considers parameters including lateral displacement, storey drift, base shear, torsional behaviour, and fundamental time period. The analysis is based on linear static wind-load evaluation of reinforced concrete moment-resisting frame structures. The results demonstrate that variation in plan geometry significantly influences the lateral response and overall structural behaviour of high-rise buildings. The rectangular configuration exhibits comparatively higher lateral displacement, while the circular configuration shows comparatively lower displacement in the analysed models. The study highlights the importance of considering plan geometry during the preliminary planning and structural design of high-rise buildings. The findings provide useful guidance for selecting an efficient plan configuration for improved wind resistance, structural safety, and serviceability.

Keywords – Building plan configuration; high-rise reinforced concrete buildings; wind-induced structural behaviour; wind loading; lateral displacement; storey drift; base shear; torsional behaviour; fundamental time period; IS 875 (Part 3):2015; moment-resisting frame.

1. INTRODUCTION

   Rapid urbanization and increasing population density in modern cities have led to the construction of high-rise buildings as an effective solution for optimal land utilization. With the increase in building height, structures become more flexible and slender, making them highly sensitive to lateral loads, particularly wind loads. Unlike low-rise buildings,

   where gravity loads dominate design considerations, the design of high-rise buildings is primarily governed by lateral forces such as wind and seismic effects.

   Wind load is one of the most critical environmental loads acting on high-rise structures. It significantly influences structural safety, serviceability, and occupant comfort. Wind effects induce lateral displacement, storey drift, torsional response, and additional stresses in structural members, which must be carefully evaluated during structural design.

   The magnitude of wind load acting on a building depends on several parameters including building height, terrain conditions, topography, wind velocity, exposure conditions, and most importantly, plan configuration of the structure. The geometry of a building plays a crucial role in determining its aerodynamic behaviour under wind action. Buildings with symmetrical plan shapes generally perform better than irregular plan configurations because they reduce torsional effects and distribute lateral forces more uniformly.

   Irregular plan shapes such as L-shape and T-shape buildings experience larger torsional moments due to eccentricity between the centre of mass and centre of rigidity. On the other hand, regular configurations such as square, rectangular, and circular shapes provide better resistance against wind forces due to uniform stiffness distribution.

   In India, wind load estimation for structural design is carried out according to IS 875 Part 3, which provides procedures for determining design wind speed, wind pressure distribution along the height of buildings, terrain effects, topographical factors, and load combinations for safe structural design.

   Therefore, it becomes essential to evaluate the influence of building plan geometry on structural response under wind loading conditions. A comparative study of high-rise buildings with different plan shapes helps in identifying the most efficient structural configuration that minimizes lateral displacement, storey drift, torsional effects, and internal forces.

   The present study focuses on analysing and comparing the behaviour of high-rise reinforced concrete buildings having different plan configurations subjected to wind loads calculated as per IS 875 (Part 3) using advanced structural analysis software such as ETABS. The results obtained from the analysis will help in understanding the influence of plan shape on wind performance and assist in selecting suitable geometries for efficient structural design of high-rise buildings.

2. METHODOLOGY AND MATERIAL CHARACTERIZATION

   1. METHODOLOGY OR STEPS

      Fig 1: Flowchart of the Structural Analysis and Comparative Evaluation Process.

      TABLE 1: GEOMETRICAL CONFIGURATION OF THE BUILDINGS

      Shape	Dimension	No. of bays
      Square	25m x 25m	7
      Rectangular	36.76m x 17m	12
      Circular	Dia -28.2m	9

   2. MODEL DETAILS

      The structural members in this project are designed using standard materials as per Indian Standards. M30 grade concrete is used for RCC members, Fe 550 grade steel is used as reinforcement. These materials provide adequate strength, durability, and wind performance for the building.

   3. STRUCTURAL SYSTEM FOR THE BUILDINGS

      The structural system for the buildings has been evolved on the basis of various aspects like functional requirements of the building, durability and life span of building, cost effectiveness and other design criteria requirements specified by discussions on number of meetings with client.

   4. RELEVANT CODES FOLLOWED FOR DESIGN

      The main design standards followed for structural design are given below, indicating their area of application.

      For Loading:

      IS 875(Part 1):1987-Dead loads. IS 875(Part 2):1987-Imposed load. IS 875(Part 3):2015-Wind Loads.

      For Design of Reinforced Concrete:

      IS 456:2000-Code of practice for plain and reinforced concrete (Fourth Revision)

   5. DESIGN PARAMETERS AND VALUES

      TABLE 2: WIND ANALYSIS AND DESIGN INPUT PARAMETERS

      Sl.No.	Input Parameter	Value
      1.	Basic Wind Speed, Vb	39
      2.	Risk Co-Efficient, K1	1.07
      3.	Topography Co-Efficient, K3	1
      4.	Terrain Category	2
      5.	Class Of Structure	B
      6.	The Value Of Height And Structure Size Factor K2	Value Varies with Height

   6. AutoCAD Layout Plan and 3d- Rendered Views of Different shaped Building

      Fig. 2: (a) Square Building – AutoCAD Layout dimension 25m x 25m – Height 41.7m

      Fig. 2: (b) Rectangular Building – AutoCAD Layout dimension

      26.76m x 17m – Height 41.7m

      Fig. 2: (c) Circular Building -AutoCAD Layout dimension Dia-28.2m – Height 41.7m

      Fig 3: (a) 3-D Rendered view of Square Building.

      Fig 3: (b) 3-D Rendered view of Rectangular Building.

      Fig 3: (c) 3-D Rendered view of Circular Building.

   7. Wind Load Acting towards Different shaped Building.

      WIND LOAD ACTING IN SQUARE BUILDING IN EVERY DIRECTION

      Fig-4 (a) Wind load in X(+) & X(-) Direction

      Fig-4 (b) Wind load in Z(+) & Z(-) Direction

      WIND LOAD ACTING IN RECTANGULAR BUILDING IN EVERY DIRECTION

      Fig-4 (c) Wind load in X(+) & X(-) Direction

      Fig-4 (d) Wind load in Z(+) & Z(-) Direction

      WIND LOAD ACTING IN CIRCULAR BUILDING IN EVERY DIRECTION

      Fig-4 (e) Wind load in X(+) & X(-) Direction

      Fig-4 (d) Wind load in Z(+) & Z(-) Direction

   8. DESIGN BASIS

      Design wind loads for the square, rectangular, and circular G+12 reinforced concrete building models are determined in accordance with IS 875 (Part 3):2015, using the relevant wind speed and site and structural factors. The models are analysed under consistent conditions, and their lateral displacement, storey drift, base shear, torsional response, and fundamental time period are compared to assess how plan configuration affects wind-induced structural behaviour. The reinforced concrete members are designed in accordance with Indian Standard Code. Other relevant codes as mentioned in the list above were also followed for specific items of work.

      Grade Of Concrete And Cover To The Reinforcement.

      The appropriate grade of concrete and nominal cover to reinforcement is governed by the

      Following main considerations:

      • Durability of Concrete

      • Fire Resistance

      • Corrosion Protection to the Reinforcement

      • Bar Size

      • Nominal maximum aggregate size

      • Proposed Grade of Concrete & Cover to Reinforcement

        Considering the nature of soil as observed in site during previous excavation for the site and the exposure conditions, fire rating, durability requirements etc. mentioned in IS Code, the proposed grade of concrete for all the reinforced concrete members is M30, and clear cover to Reinforcement for various items are as follows:

      • Roof and plinth Beams 25mm

      • Columns & Pedestals 40mm

      • Slabs 20mm

      • Footings 50mm

      • Raft 75mm

   Materials

   • Materials used as constituents of concrete shall be as per clause of IS codes. The properties of hardened concrete shall be as per IS code and other relevant clauses shall be considered.

   • Reinforcement

   • The following types of reinforcement bars shall be used:

   • 1. Thermo-mechanically treated (TMT) Confirming to IS: 1786-1985 (fy = 550 MPa)

   • 2. Deformed bar Confirming to IS: 1786-1985 (fy = 415 MPa)

   • Reinforcement Bars of size 8 mm, 10 mm, 12 mm, 16mm, 20mm, 22mm and 25mm will be used. Welded wire mesh shall not be used for structural members. Only lapped splices/Coupler shall be used.

   • Admixtures

   • The concrete slump shall in general be in the range of 75mm and 125mm depending on reinforcement congestion, ambient temperature and other placement, transporting and compaction considerations.

   • Cement

   • Use of Ordinary Portland Cement as per NBC is recommended for all elements of the structure is recommended.

   • Structural Dimensioning

   • In addition to the requirements of loads and stresses the minimum structural dimensions are also governed by other considerations like fire resistance, size of aggregates, reinforcement detailing, etc. Minimum width of beams & columns shall not be less than 250mm from above requirements. The minimum thickness of any structural element shall conform to NBC. The minimum thickness of various elements shall also meet the fire resistance requirements of IS: 8110-Part 1-1985. All the reinforced concrete elements of the building will be designed for mild condition of exposure and a fire resistance of 1.5 hours.

3. RESULT

   1. Maximum Node Displacement Comparison

      TABLE 3: MAXIMUM NODAL DISPLACEMENT

      Parameter	Square Building	Rectangular Building	Circular Building	Best Performance
      Maximum X displacement (mm)	92.630	55.529	76.187	Rectangular
      Maximum Y displacement (mm)	57.231	25.668	32.368	Rectangular
      Maximum Z displacement (mm)	46.445	41.002	55.958	Rectangular
      Maximum resultant displacement (mm)	93.189	57.276	78.076	Rectangular

      TABLE 4: ROTATIONAL RESPONSE COMPARISON

      Parameter	Square Building	Rectangular Building	Circular Building	Lowest Rotation
      Maximum rX (°)	0.083	0.113	0.138	Square
      Minimum rX (°)	-0.083	-0.113	-0.138	Square
      Maximum rY (°)	0.022	0.017	0.022	Rectangular
      Minimum rY (°)	-0.022	-0.020	-0.021	Rectangular
      Maximum rZ (°)	0.139	0.121	0.165	Rectangular
      Minimum rZ (°)	-0.139	-0.121	-0.64	Rectangular

      Maximum Y displacement (mm)	57.231	25.668	32.368	Rectangular
      Maximum Z displacement (mm)	46.445	41.002	55.958	Rectangular
      Maximum resultant displacement (mm)	93.189	57.276	78.076	Rectangular
      Maximum rX (°)	0.083	0.113	0.138	Square
      Maximum rY (°)	0.022	0.017	0.022	Rectangular
      Maximum rZ (°)	0.139	0.121	0.165	Rectangular
      Maximum FX reaction (kN)	77.628	50.422	139.904	Rectangular
      Maximum FY reaction (kN)	4140	4200	4660	Square
      Maximum FZ reaction (kN)	2640	2980	2810	Square
      Maximum MX (N- m)	2.13×10	3.09×10	3.26×10	Square
      Maximum MY (N- m)	1.28×10	2.25×10	1.98×10	Square
      Maximum MZ (N- m)	116×10³	74.2×10³	353×10³	Rectangular

      TABLE 6: MAXIMUM RESULTANT DISPLACEMENT (MM)

      Square 93.189

      Circular 78.076

      Rectangular 57.276

      TABLE 7: MAXIMUM REPORTED SUPPORT REACTION COMPARISON

      Parameter	Square	Rectangular	Circular	Lowest
      Maximum FX (kN)	77.628	50.422	139.904	Rectangular
      Maximum FY (kN)	4140	4200	4660	Square
      Maximum FZ (kN)	2640	2980	2810	Square

      Parameter	Square	Rectangular	Circular	Lowest
      Maximum MX (N-m)	2.13 × 10	3.09 × 10	3.26 × 10	Square
      Maximum MY (N-m)	1.28 × 10	2.25 × 10	1.98 × 10	Square
      Maximum MZ (N-m)	116 × 10³	74.2 × 10³	353 × 10³	Rectangular

      TABLE 8: MAXIMUM SUPPORT MOMENT COMPARISON

4. CONCLUSION

TABLE 9: PERFORMANCE AND CONCLUSION

ACKNOWLEDGMENT

The authors would like to thank the Department of Civil Engineering and the management of Birsa Institute of Technology (B.I.T.) Sindri, Dhanbad, Jharkhand for providing the necessary lab facilities, computational facilities, analytical tools and software supports to perform this research work. The authors are thankful to Assistant Professor Dr. Jitu Kujur for her valuable guidance, continuous support and constructive suggestions and encouragement during the study. The authors also thank the faculty members and technical staff members of the Department of Civil Engineering throughout the period of research.

REFERENCES

1. Muhanad M.M. Al-Deraan and P. Srinivasa Rao (2013)

A Comparative Study of Wind Forces on Tall Building by Static Method and Dynamic

Method per IS 875-Part III Journal: IJSETR

Very relevant for methodology.

1. Muhanad M.M. Al-Deraan and P. Srinivasa Rao (2013)

   A Comparative Study of Wind Forces on Tall Building as per IS 875-Part III and Draft Code Using Gust Factor Method Useful for code evolution discussion.

2. Bodhisatta Hajra and P.N. Godbole (2006)

   Along Wind Load on Tall Buildings Indian Codal Provisions Good for codal theory background.

3. Shams Ahmed and S. Mandal (2017)

   Comparative Study of Along-Wind Response of Major International Codes with Indian Code

   Useful for comparative code review.

4. Chidhanandha H. and B.S. Suresh Chandra (2019) Comparative Study of Tall Structures with Plan Irregularity Subjected to Wind Load

   Directly linked to your thesis topic.

5. Wind effects on Z-plan shaped tall building case study (2016) Useful for irregular plan wind behaviour.

6. Bin Yang (2021) – Wind Engineering for High-rise Buildings A Review Excellent review paper for literature chapter.