Structural Performance Evaluation of Multi Storey Building Considering Different Sloping Angles with Bracing Systems Using Tekla Structural Designer

Abstract

This study investigates the seismic behavior of a structure on sloping ground with inclinations of 0°, 5°, and 10°, analyzed in TEKLA Structural Designer using the Response Spectrum Method for Seismic Zone II. Results from graphs and tables highlight variations in structural performance under different slopes. Case 2 (5° slope) exhibits the highest effective seismic weight of 91,019 kN, resulting in maximum base shear forces of 2,204.60 kN (code-based) and 1,750.70 kN (modal analysis). Its higher mass and stiffness make it the most seismically demanding and dynamically stable structure, showing the shortest natural period, highest frequency, and significant mass participation in the initial modes. Case 2 also demonstrates the highest storey shear in the Y-direction (2,961.86 kN), storey sway in both X (260.53 mm) and Y (269.19 mm) directions, and seismic drift of 4 mm in the Y-direction. Case 1, on flat ground, records maximum shear in the X-direction (2,534.52 kN) and maximum drift of 3 mm in X. The maximum storey force in the X-direction occurs in case 3 (503.67 kN). Case 2 also demands the most reinforcement (213,156.33 kg), confirming that sloped ground increases stiffness, mass, and overall seismic demand.

Introduction

Rapid urbanization in hilly areas has increased multistorey construction on slopes, which introduces geometric, mass, and stiffness irregularities, making such buildings more vulnerable to seismic forces. Slope angle affects dynamic properties like natural frequency, mode shapes, and base shear, influencing earthquake response. Past earthquakes show slope-based buildings often suffer torsional effects, uneven foundations, and irregular load distribution.

This study uses Tekla Structural Designer (TSD) to perform a comparative seismic analysis of a G+6 RCC building on slopes of 0°, 5°, and 10° with bracings. TSD allows integrated 3D modeling, automated load calculations, code-compliant analysis, and design evaluation, streamlining assessment of seismic performance.

Building Model:

• RCC structure, G+5+terrace, total height 23.9 m.

• Floor height 3.2 m, base height 1.5 m, M30 concrete, Fe550 steel.

• Columns, beams, bracings, and slab designed as per IS codes.

• Loads include dead, live, and seismic loads (IS 1893-2016, Seismic Zone II, Medium soil).

Analysis Methodology:

• Response Spectrum Method used for seismic evaluation.

• Three models developed for 0°, 5°, and 10° slopes.

• Load combinations and static/dynamic loads applied uniformly.

• Key performance parameters analyzed: storey drift, lateral displacement, shear force, and mode shapes.

Results and Discussion:

• Seismic behavior varies significantly with slope angle.

• Increased slope leads to higher storey drift, lateral displacement, and altered mode shapes.

• Comparative analysis helps understand slope-induced seismic responses and informs safer, efficient design practices for RCC buildings on hilly terrain.

Conclusion

In this study, we examined how the structure behaves on different sloping ground conditions by considering slopes of 0°, 5° and 10°. The analysis was carried out in TEKLA STRUCTURAL DESIGNER using the Response Spectrum Method of Analysis (RSMA) for seismic Zone II. The results have been compared through graphs and tables, which provided a clear understanding of the structure on varying slopes. Based on these observations, the following conclusions were drawn. 1) In Case 2, the structure carries the highest effective seismic weight of 91,019.00kN, which results in the largest base shear forces 2,204.60kN from code-based calculations and 1,750.70kN from modal analysis. This indicates that Case 2 more stiffest among the three model. 2) The modal response spectrum analysis of Case 2 shows the maximum values, with higher modal base shear at the top levels and a more uniform distribution of shear across the structure. 3) The maximum values for modal frequencies Case 2 have the shortest natural period and the highest frequency, indicating a dynamically stable and well-balanced structure with efficient seismic performance. 4) The maximum values for storey force in X-direction are maximum for Case 3 of 503.67kN and maximum storey force in the Y-direction is maximum for Case 2 of 572.86kN on sloped ground with bracings. 5) The maximum values for storey shear in X-direction are maximum for Case 1 of 2534.52kN and maximum shear force in the Y-direction is maximum for Case 2 of 2961.86kN on sloped ground with bracings. 6) The maximum values for storey sway in X-direction are maximum for Case 2 of 260.53 mm and maximum storey sway in the Y-direction is maximum for Case 2 of 269.19mm on sloped ground with bracings. 7) The maximum values for seismic drift in X-direction are maximum for Case 1 of 3 mm and maximum seismic drift in the Y-direction is maximum for Case 2 of 4 mm on flat ground with bracings. 8) The maximum material listing values in Case 2 is 213156.33kg indicates higher reinforcement demand on sloping ground with bracings.

References

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Copyright

Copyright © 2025 Mahesh S Mudigowdar, Savan R G Basavaraj . 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.