Evaluation of Structural Dynamics and Equilibrium State, with Case Study of Large Cantilever Projection for a 10- Storey Reinforced Concrete Building in Lagos, Nigeria

This study evaluates the equilibrium state and dynamic response of large cantilever projections (1 m, 2 m, 4 m, 6 m) in a ten-storey reinforced concrete building located in Lagos State, Nigeria. The research was motivated by the increasing architectural trend of wide cantilever balconies and façades in high-rise buildings, which often lead to excessive deflection, loss of equilibrium, and cracking when conventional reinforcement systems are adopted. The structural assessment was carried out in accordance with Eurocode 2 (EN 1992-1-1: 2004), applying finite-element analysis for the reinforced concrete (RC) models and manual analytical procedures for the post-tensioned (PT) systems. Both RC and PT slabs were evaluated under identical loading and boundary conditions. The investigation covered moment–shear–reaction equilibrium, deflection behaviour, and crack-width control, based on C30/37 concrete and Grade 460 steel reinforcement. Results show that RC slabs developed higher bending moments and deflections with increasing projection length, while PT slabs sustained equilibrium more effectively through internal compressive actions generated by prestressing. Overall, PT systems achieved over 50 % reduction in deflection, minimised cracking, and improved serviceability. The study concludes that manually designed PT slabs provide a stable equilibrium state and a structurally efficient solution for cantilever projections exceeding 2 m, ensuring safer and more economical multi-storey construction.