Effect of Setbacks on Lateral Displacement in G+6 Multistorey Structure Using STAAD Pro

Abstract

The multistorey structures/ buildings solve the population\'s living problems increasing daily. Many clients require more area for commercial purposes such as parties or other celebrations. Therefore, structures are designed with floating columns and setbacks. These elements generate the geometrical irregularity in the structures. Therefore, the present research work has determined the impact of setbacks on the lateral displacement of the structure. The A/L ratios of setbacks are 0.1, 0.125, 0.133, 0.167, 0.2 and 0.233 considered in the design and analysis of structure. The lateral displacement results of irregular structures (with setbacks) have been compared with regular structures (without setbacks) and provisions given in the code.

Introduction

I. INTRODUCTION

A. General

A three-dimensional structure with multiple stories and vertical move mentutilizing stairsand lifts are known as a multistorey building. The multistorey building is generally designed to serve as a commercial mall, residential apartment, commercial apartment, hospital,etc. The construction speed of multistorey buildings is faster than other conventional buildings due to the high level of pre-fabrication material, accuracy in design, riskless construction, and best quality checks with the help of consulting agencies. Figure 1.1 shown below is a typical 3D multistoried building designed on software.

II. MODELLING AND ANALYSIS OF STRUCTURES

In the present research work, for determining the effect of setbacks, two types of G+6 storey structures having the length of 30m and 40m have been designed and analyzed using STAAD Pro. The structures are designed for aspect ratio (A/L) of 0.1, 0.125, 0.133, 0.167, 0.200, and 0.233. Six structures with setbacks at 1st, 2nd, 3rd, 4th, 5th, and 6th storey have been designed and analyzed for each A/L ratio, and displacement results have been obtained.

In addition, two bare frame G+6 storey structures have been developed and analyzed to map the comparison with structures having setbacks. However, the displacement of G+6 bare frame structures has been calculated using IS code 1893:2016 formula of 0.004*height of storey*number of the storey (i.e., 0.004*3500*7 = 98mm). Furthermore, the displacement obtained from IScodal formula, bare frame structure, and structures having setbacks has been compared. The comparison is mapped as –

1. Comparison of results of lateral displacement for Constant A/L ratio.
2. Comparison of results of lateral displacement for varying A/L ratio.

Conclusion

The following conclusions are mapped from the comparative study of lateral displacement results. 1) The lateral displacement results of the G+6 storey structure having an A/L ratio of 0.1 to 0.167 (L=30m) show that the lateral displacement increases if the setbacks are provided up to the fifth and sixth storey. These kinds of structures are having lateral displacements within permissible limits as per IS code and hence, safe. Furthermore, the G+6 storey structure having an A/L ratio of 0.2 and 0.233 (L=30m) achieves more lateral displacement than the regular structure and the Indian standards, which makes the structure unsafe. G+6 storey structures having an A/L ratio of 0.2 and 0.233 are unsafe if the setbacks are provided at the sixth and fifth storey, respectively. 2) On the other hand, lateral displacement results of the G+6 storey structure having an A/L ratio of 0.1 to 0.133 (L=40m) show that the lateral displacement increases if the setbacks are provided up to the fifth and sixth storey. These kinds of structures are having lateral displacement within permissible limits as per IS code and hence, safe. Furthermore, the G+6 storey structure with an A/L ratio of 0.2 and 0.233 (L=40m) achieves more lateral displacement than the regular structure and the Indian standards, representing the structure as unsafe. The G+6 storey structure having an A/L ratio of 0.233 is identified as a critical structure because the lateral displacement is found more than regular structure and codal provisions, i.e., 98.01mm (case 1+6), 100.16mm (case 2+5), 101.36mm (case 3+4), 103.97mm (case 4+3), 110.26mm (case 5+2), 121.38mm (case 6+1). 3) The comparison of G+6 storey structure having L=30m and L=40m shows that if the length of the structure increases, the A/L ratio decreases for safe design and structure. In other words, the G+6 storey structure (L=30m) is safe for A/L ratios of 0.1, 0.125, 0.133, and 0.167, but the G+6 storey structure (L=40m) is only safe for A/L ratios of 0.1, 0.125, and 0.133. 4) The comparison of results of lateral displacement for G+6 storey structure with varying A/L ratios shows that lateral displacement increases with A/L ratio in both L=30 and L=40m structures. 5) Finally, the present study has concluded that the A/L ratio of setbacks affects the lateral displacement of the structure. The G+6 storey structure having an A/L ratio of less than 0.167 (for L=30m) and 0.133 (for L=40m) are safe as per the Indian provisions and may be constructed.

References

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Copyright

Copyright © 2023 Manoj Kumar, Dr. K. S. Grover . 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.