The Effect of Soil Improvement on the Structural Response of a Retrofitted Building with Shotcrete Panels

Countries such as Turkey, Pakistan, Italy, and Chile, where low-strength reinforced concrete (RC) buildings are common in seismically active regions, face significant seismic hazards due to substandard structural design, poor material quality, and unfavorable geotechnical conditions. The interaction between liquefaction-prone soft soils and RC frames with insufficient lateral load resistance often results in vulnerabilities such as excessive inter-story drifts, differential settlements, and foundation rotations. Effective retrofitting strategies and soil improvement techniques are imperative to improve seismic resilience in such scenarios. This research encompasses not only the implementation of structural retrofitting measures but also the improvement of soil properties to assess their combined impact on seismic performance of building. The retrofitting approach involves installing shotcrete panels within frames and applying reinforced concrete (RC) jacketing around the surrounding columns. This method is implemented on a 2D RC frame structure with a shallow foundation resting on soft soil. Given the susceptibility of soft soils to liquefaction under strong ground shaking, stabilization is achieved through the application of jet grouting techniques. This study utilizes analytical modeling and nonlinear dynamic time history analysis (NDTHA). The installation of shotcrete panels reduced maximum inter-story drift for both soft and improved soil conditions. The findings indicate that employing shotcrete panels as a retrofitting technique offers a viable strategy for significantly enhancing foundation stability, particularly in complex soil conditions. Furthermore, soil improvement plays a crucial role in mitigating foundation rotation and may serve as an effective compensatory measure for inherently less robust foundation designs, such as single-footing systems.