A Material Optimized Design Strategy for Mitigating Soft-Story Vulnerability Using Hollow Concrete Columns

Soft-story irregularity is a critical structural concern in multi-story buildings, especially when the first-floor height is significantly greater than the upper floors. This architectural feature reduces lateral stiffness, increasing vulnerability to damage during seismic events. Traditional retrofitting methods, such as shear walls or steel bracing, can enhance stability but typically require large amounts of steel and cement, contributing to high embodied energy, CO₂ emissions, and environmental degradation.This study proposes a material-optimized design approach specifically aimed at mitigating soft-story vulnerability by using hollow reinforced concrete columns with the same concrete volume as conventional solid columns. A mid-rise, symmetric building was modeled using ETABS 2016 to compare the seismic performance between hollow and solid column systems. Results showed that hollow columns increased moment of inertia by up to 196.68%, significantly enhancing story stiffness and reducing displacements by up to 26.4%. The larger cross-section of hollow columns also lowered beam shear forces, bending moments, and torsion, contributing to greater structural stability and economic efficiency. The results confirm that hollow columns are capable of effectively mitigating the soft-story problem without requiring additional material.By achieving better seismic performance without increasing material use, this approach supports more resilient and environmentally responsible building practices, offering a promising alternative to conventional methods for mitigating soft-story vulnerability.