Analysis and Design of Multi-Story Building with Grid Slab

Abstract

The rapid growth of urbanization has led to a significant increase in the construction of multi-story buildings, demanding innovative and economical structural systems. One such system is the grid slab, which provides enhanced load distribution and structural stiffness compared to conventional slab systems. This study focuses on the analysis and design of a multi-story building incorporating a grid slab system, aimed at optimizing strength, stiffness, and cost efficiency. The analysis was carried out using ETABS 2020 software, considering dead load, live load, wind load, and seismic load as per IS 456:2000, IS 875 (Part 1–3):2015, and IS 1893:2016. The results show that the grid slab system improves structural performance by reducing slab thickness and controlling deflection, making it a suitable alternative for medium- to high-rise structures.

Introduction

Rapid urbanization and limited land availability have increased demand for high-rise buildings, where the choice of slab system affects structural performance and economy. Traditional slabs often lead to excessive deflection and higher material usage for large spans. Grid slabs (waffle slabs), consisting of perpendicular ribs, reduce slab weight while maintaining strength, offering architectural flexibility and efficient load transfer.

Objectives: The study aimed to design a G+10 RC building with a grid slab, analyze its structural behavior under various loads using ETABS, compare it with conventional slabs in terms of deflection, bending moments, and material use, and optimize for cost-effectiveness and serviceability.

Methodology:

• The building (30 × 25 m, 3.2 m storey height) was modeled in ETABS 2020 in Seismic Zone III.

• Loadings included live, floor finish, seismic, and wind loads per IS codes.

• Both linear static and dynamic analyses were performed.

• Slabs, beams, columns, and foundations were designed with optimized reinforcement.

Results:

• Grid slabs reduced self-weight by 20–25% and deflections by 30–40% compared to conventional slabs.

• Bending moments in central panels decreased, allowing optimized reinforcement.

• Storey drift remained within IS limits, ensuring lateral stability.

• Overall material usage and construction cost were reduced.

Design Highlights: Slab thickness 110 mm (ribs 300 mm deep × 150 mm wide), beam 300 × 600 mm, column 500 × 500 mm, isolated footings designed per soil capacity.

Advantages: Reduces dead load, enhances aesthetics and architectural flexibility, improves deflection control, minimizes material use, boosts seismic performance, and suits long-span structures like auditoriums, offices, and parking decks.

Conclusion

The present study concludes that the grid slab system is an efficient and economical structural option for multi-story buildings. The grid slab reduces self-weight, enhances stiffness, and minimizes deflection. The system satisfies all the strength and serviceability requirements prescribed by IS codes. Overall, the grid slab proves to be a superior alternative to traditional slab systems for medium and high-rise structures.

References

[1] IS 456:2000 – Plain and Reinforced Concrete – Code of Practice. [2] IS 875 (Part 1–3):2015 – Code of Practice for Design Loads (Other than Earthquake) for Buildings and Structures. [3] IS 1893 (Part 1):2016 – Criteria for Earthquake Resistant Design of Structures. [4] IS 13920:2016 – Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces. [5] Punmia, B.C., Jain, A.K., and Jain, A.K., Limit State Design of Reinforced Concrete, Laxmi Publications. [6] Varghese, P.C., Advanced Reinforced Concrete Design, Prentice Hall of India. [7] ETABS 2020 User Manual, Computers and Structures Inc. (CSI).

Copyright

Copyright © 2025 Gonuru Shirisha , Mr. Ajit Kumar Dey. 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.