Comparison of Traditional Structural Systems and Flat Shell Systems in Terms of Construction Time and Cost in Residential Buildings

Abstract

The purpose of this study is to compare structural performance, construction time, and total cost between traditional building systems and flat shell systems in residential construction. This analytical–descriptive study was conducted using nonlinear numerical analysis in Abaqus and limited field observations. The models consisted of a three-story masonry building and a flat concrete shell system with a thickness of 7–10 cm. Cost estimation was performed using the national schedule of rates and engineering quantity surveying. Seismic behavior was assessed through friction pendulum isolation modeling and the Iranian Standard 2800 spectrum. Thermal loading, concrete type C25 properties, soil type III characteristics, and the steel shell fabrication process—including cutting, welding, assembly, and quality control—were also evaluated. Results indicated that traditional systems, due to large wall thickness, heavy weight, and weak tensile and shear resistance, perform poorly under seismic forces. In contrast, the flat shell system, benefiting from reinforced concrete and high ductility, demonstrated significantly improved performance. Fire analysis showed that traditional systems become unstable within 10 minutes, while shell systems maintain integrity longer due to concrete confinement and increased buckling capacity. Economically, steel consumption in the shell system was reduced by about 55% compared with steel structures, and overall construction costs were approximately 35% lower than traditional systems. Moreover, diagonal stiffener connections exhibited 30% higher load capacity compared with parallel stiffeners. The study concludes that flat shell systems offer superior seismic resistance, thermal behavior, material efficiency, and cost-effectiveness compared with traditional construction methods. Proper connection detailing, well-designed shell geometry, and nonlinear analysis significantly enhance structural safety and overall performance.