Abstract: Nowadays, Due to the increasing population and limited land availability, tall buildings have become a necessary feature in metropolitan areas. As a result, vertical expansion is often a more affordable and practical option than spreading out horizontally, particularly when considering proximity and accessibility to the city. Diaphragms function as lateral load-resisting systems by connecting the joints of a floor, thereby transferring inertial forces from one structural element to another. The podium’s underground perimeter walls and diaphragm function together as a rigid box system. That enhances the lateral load resistance. The podium develops an internal resisting couple that produces an effect called the backstay effect, and its action is balancing in nature against the acting lateral forces, generated by wind and seismic activity. This article examines multi-Storey models that incorporate spring action at the podium level and investigates the effect of different podium shapes and grading in a vertical direction in accordance with IS: 16700:2017, “Criteria for Structural Safety of Tall Concrete Buildings,” India, Bureau of Indian Standards, 2017. The study finds that semi-rigid action at the podium level enhances the backstay effect in comparison to traditional rigid action. Furthermore, the investigation shows that the podium shape and grading improve the shear-reversal effect, leading to reduced base shear and base moment.

Keywords: Back-stay effect, tall structures, large podium structures, shear-reversal.

| DOI: 10.17148/IARJSET.2023.10459