Analysis and Design of Shear Wall with Openings and Bracings in Multi-Storey Irregular Building

Abstract

At present days, constructing a structure with all the regular configurations is not feasible in most of the cases due to the irregular plot dimensions, aesthetic visual and functional requirements in the urban cities. The structure with more irregular configuration either horizontally or vertically are more vulnerable to earthquake & wind forces which leads to collapse of structure, property loss and casualties. When an earthquake occurs, nearly all buildings in the area are exposed to seismic forces. When a tall structure is subjected to lateral or torsional deflections under the action of seismic loads, the resulting oscillatory movement can induce a wide range of response in the building occupants. Therefore, lateral stiffness is an important consideration in the design of multi storey structures. The improvement of reinforced concrete frame structure against lateral loading can be achieved by providing shear walls and cross bracings. In this study, a G+19 storey important service and community building with re-entrant corners has been analyzed and designed with shear wall with openings and cross bracings. Significance of shear walls and bracings has been studied with the help of nine models. This analysis and design was made as per IS 1893:2016 codal provision by using ETABS 20 software. The building models are analyzed by response spectrum method using ETABS software. The main parameters compared in this study are lateral displacement, storey drift, base shear, overturning moment and storey stiffness. Shear wall without openings shows better performance when compared to all models. Compared to bare frame, displacement is reduced by 38.6%, drift reduced by 37.6%, storey shear increased by 114.8% and storey stiffness increased to 25.6x10? kN/m. Performance of building with the combination of shear wall with openings and bracings is good. Compared to bare frame, displacement is reduced by 37.2%, drift reduced by 34.4%, storey shear increased by 74% and storey stiffness increased to 19.4x10? kN/m. The results of model 4 and model 9 are almost equal. Combination of shear wall with openings and bracings will helps to achieve the economy and also increases the strength.

Introduction

The study compares the performance of buildings with different lateral load-resisting systems, including shear walls (with and without openings) and bracings, against a bare frame (no lateral load resistance). Key findings include:

1. Shear Wall Placement: The optimal placement of shear walls and bracings is at the corners of the building to maintain symmetry and enhance performance.

2. Bare Frame Performance:

   • Serviceability: Maximum displacement of 145.66 mm exceeds the allowable limit, and the stiffness is only 6.7x10? kN/m.

   • Strength: Maximum displacement of 171.98 mm, and stiffness is 4.4x10? kN/m, which is lower than the building with shear walls or bracings.

3. Shear Wall with Openings:

   • Serviceability: Displacement reduced by 33.8%, drift by 31.7%, storey shear increased by 87%, and storey stiffness increased to 20.5x10? kN/m.

   • Strength: Displacement reduced by 40.3%, drift by 45.2%, storey shear increased by 108.1%, and storey stiffness increased to 16.6x10? kN/m.

4. Shear Wall without Openings (Best Performance):

   • Serviceability: Displacement reduced by 38.6%, drift by 37.6%, storey shear increased by 114.8%, and storey stiffness increased to 25.6x10? kN/m.

   • Strength: Displacement reduced by 43.8%, drift by 48.9%, storey shear increased by 127%, and storey stiffness increased to 19.1x10? kN/m.

5. Bracings:

   • Serviceability: Displacement reduced by 24.4%, drift by 22.6%, storey shear increased by 31.9%, and storey stiffness increased to 11.1x10? kN/m.

   • Strength: Displacement reduced by 33.3%, drift by 38.4%, storey shear increased by 51.5%, and storey stiffness increased to 9.5x10? kN/m.

6. Combination of Shear Wall with Openings and Bracings:

   • Serviceability: Displacement reduced by 37.2%, drift by 34.4%, storey shear increased by 74%, and storey stiffness increased to 19.4x10? kN/m.

   • Strength: Displacement reduced by 39.8%, drift by 44.2%, storey shear increased by 82.2%, and storey stiffness increased to 14.3x10? kN/m.

7. Impact of Openings in Shear Walls: The presence of openings in shear walls provides similar results to shear walls without openings but allows for more economical design without compromising performance.

Conclusion

Shear walls and bracings are placed in such a way that the symmetry of the structure is maintained. From the comparison of the results it is found that the optimum location of shear wall with openings, without openings and bracings is found at the corners of the building. The performance of building without any lateral force resisting member is poor. For serviceability criteria, the maximum displacement for bare frame is 145.66 mm which exceeds maximum limit and stiffness for the bare frame is 6.7x10? kN/m which is less compared to the building with shear walls and bracings. For strength criteria, the maximum displacement for bare frame is 171.98 mm and stiffness is 4.4x10? kN/m. Shear wall with openings shows better performance. For serviceability criteria, after comparing to bare frame displacement is reduced by 33.8%, drift reduced by 31.7%, storey shear increased by 87% and storey stiffness increased to 20.5x10? kN/m. For strength criteria, after comparing to bare frame displacement is reduced by 40.3%, drift reduced by 45.2%, storey shear increased by 108.1% and storey stiffness increased to 16.6x10? kN/m. Shear wall without openings shows better performance when compared to all models. For serviceability criteria, after comparing to bare frame displacement is reduced by 38.6%, drift reduced by 37.6%, storey shear increased by 114.8% and storey stiffness increased to 25.6x10? kN/m. For strength criteria, after comparing to bare frame displacement is reduced by 43.8%, drift reduced by 48.9%, storey shear increased by 127% and storey stiffness increased to 19.1x10? kN/m. After providing the bracings, displacements are within the limits. For serviceability criteria, after compared to bare frame displacement is reduced by 24.4%, drift reduced by 22.6%, storey shear increased by 31.9% and storey stiffness increased to 11.1x10? kN/m. For strength criteria, after compared to bare frame displacement is reduced by 33.3%, drift reduced by 38.4%, storey shear increased by 51.5% and storey stiffness increased to 9.5x10? kN/m. Building with the combination of shear wall with openings and bracings shows better performance. For serviceability criteria, after comparing to bare frame displacement is reduced by 37.2%, drift reduced by 34.4%, storey shear increased by 74% and storey stiffness increased to 19.4x10? kN/m. For strength criteria, after comparing to bare frame displacement is reduced by 39.8%, drift reduced by 44.2%, storey shear increased by 82.2% and storey stiffness increased to 14.3x10? kN/m. The presence of openings in shear wall give approximately same result as that of the shear wall without opening. So by providing openings in shear wall ultimately helps to achieve the economy. From the results we can say that, If the building is safe in limit state of strength then it is automatically safe in limit state of serviceability.

References

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Copyright

Copyright © 2025 Kum. K Navyasri. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.