Seismic Retrofitting of a Building using Steel Bracing and Concrete Jacketing (with Case Study: A 5 Storey Building at Ibadan, Nigeria)

Seismic retrofitting is a crucial intervention for enhancing the resilience of existing buildings in seismically active regions. This study focuses on the retrofitting of a three-storey commercial building in Ibadan, Nigeria, utilizing steel bracing and concrete jacketing techniques. Although Ibadan is not traditionally classified as a high-seismic zone, recent global and regional studies highlight the need to evaluate the potential impact of seismic loads on structures. This paper methodology entails retrofitting design, including assessment of existing structural conditions, selection of appropriate retrofitting techniques, numerical modelling using ETABS software, and a comparative analysis of retrofitted and unretrofitted models, also key structural response parameters such as base shear capacity, inter-storey drift, lateral displacement, and stiffness degradation were evaluated. The study further considers soil-structure interaction (SSI) effects, given the implications of seismic loading on foundation bearing capacity and ground settlement. The results expressed that retrofitting significantly enhances the structural integrity of the building, reducing lateral displacements and improving seismic resistance, and reveals that while the soil’s bearing capacity is sufficient under normal conditions, seismic loading could induce reductions in soil strength, emphasizing the importance of long-term ground improvement measures. The study concludes that steel bracing and concrete jacketing provide effective solutions for improving seismic resilience. Recommendations include implementing regular structural health monitoring, adopting performance-based design approaches, and considering soil stabilization techniques to ensure sustained structural stability under potential seismic events.