The IUP Journal of Structural Engineering
Evaluation of Magnification Factor for OGS Buildings with Combined Effect of Flexure and Torsion

Article Details
Pub. Date : Oct, 2021
Product Name : The IUP Journal of Structural Engineering
Product Type : Article
Product Code : IJSE11021
Author Name : Manjunath S Makari, V D Gundakalle and Hemant Sonawadekar
Availability : YES
Subject/Domain : Science and Technology
Download Format : PDF Format
No. of Pages : 9



Multi-storey buildings are in high demand owing to demographic growth and also because open ground floor parking and a reception hall are unavoidable. Usually a framed structure, including a soft storey at the bottom, is tested by neglecting the rigidity of infill to study the conduct of Open Ground Structures (OGS). Besides soft storey, asymmetric constructions are also inevitable owing to functional diversity and architectural desires. Therefore, the shear force and Bending Moment (BM) of the columns positioned on the ground floor must be amplified according to Indian Norms. Recommendation for Magnification Factor (MF) as per IS:1893 (2002) is 2.5, and this MF must be applied to the BM and shear force of ground floor columns. Due to the combined impact of soft storey and torsion, attempts are made to assess the MF in the current work. The torsional reaction of structures under seismic excitation is due to an uneven configuration, resulting in a non-symmetrical distribution of mass and rigidity. A linear Response Spectrum Analysis (RSA) assessment is performed on five floor structure and imposed with a seismic excitation of 5%, 10% and 15%. Comparisons are made between regular eccentric structure and structures with varying eccentricity. It is deduced from the assessment that the MF suggested by IS: 1893 (2002) of 2.5 is high. And there is no need to apply MF for beams, as it will increase the seismic demand in columns.


There is a huge demand for multi-storey structures due to the significant floor region and its significance in urban regions. However, these structures are more vulnerable to lateral forces, and structural design must be carried out in order to combat them in the most efficient and economical way. Unless properly designed, a full collapse may ensue. Research conducted in the field of earthquake authenticates that there is more damage to structures which are irregular. Example of such irregularity is soft storey, and in addition, if additional eccentricity is induced, then the effect of earthquake on structure is augmented (Mallick and Severn, 1967).


Open Ground Structures (OGS) building, Bare frame, Torsion, Eccentricity, Magnification Factor (MF), Macro model, Response Spectrum Analysis (RSA)