Comparative Seismic Analysis of Multistory Structures Incorporating Floating Columns and Conventional Column Systems

Abstract

Buildings are representation of modern city and as such are an achievement of structural engineering. The seismic behavior of a building during earthquakes depends on its shape, size and geometry, in addition to how the earthquake forces are carried tothe ground. Hence, the structural engineers must workto make sure that the features which are not favorable are avoided and a good building configuration is chosen at the planning stage itself. Nowadays multi-storey buildings in urban cities are required to have column free space due to shortage of land, population and for functional and aesthetic requirements. Floating columns are an important feature in today’s world of multi-storeyed buildings in urban India and are highly unsafe in buildings built in seismically active areas. In this paper analysis using response spectrum method is done for a multi-storeyed building with and without floating columns. This paper presents comparative study of a G+06 storied building with external and internal floating columns and regular columns with seismic behavior. This work includes the analysis and design of the floating column and regular column structures by using STAAD pro software.

Introduction

The text discusses the seismic behavior and structural analysis of a reinforced concrete (RC) building under earthquake loads in India, a country divided into seismic zones ranging from Zone II to Zone V according to the IS 1893:2002 code.

The project involves a 6-story RC building (25.2m length, 16m width, 16.8m height) with a medium soil type, analyzed as an Ordinary Moment Resisting Frame (OMRF) using STAAD Pro software. The analysis is performed for two seismic zones (Zone II and Zone III) using multiple load combinations that include dead load, live load, and earthquake loads in X and Z directions.

Four structural cases are studied:

1. Normal RC building without floating columns,

2. Building with external floating columns,

3. Building with internal floating columns,

4. Building with both external and internal floating columns.

Key parameters analyzed include displacement (X and Z directions), axial forces, shear forces, and bending moments in columns and beams, specifically focusing on corner and intermediate columns and beams. The results, shown through various graphs, compare structural responses under different seismic zone conditions and configurations.

Conclusion

1) In case 4(External and Internal Floating column), increases the Mx and Mz value at all the floor for both the zones i.e. Zone II and Zone III. 2) Provision of Case 4 (External and Internal Floating columns) and case 3(Internal Floating Columns) may increase Axial Force Fx and Shear in z direction (Fz) at all floors. 3) 1.5(DL+EQZ) or 1.5(DL+EQX) these load combinations are found critical, depending on position of floating columns. 4) Provision of Case 2 (External Floating columns) and Case 4 (External with Internal Floating columns) may increase displacements at various nodes.

References

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Copyright

Copyright © 2025 Prof. Pallavi Bhende, Mr. Atul Kawde. 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.