Investigation of the effect of different slab types on construction cost under variable ground types according to TBDY 2018

In Türkiye, ensuring seismic safety is as crucial as achieving economic and sustainable construction. Especially in a seismically active country with diverse geotechnical profiles like Türkiye, considering local soil conditions has become essential in structural design. Rising construction costs highlight the need for efficient use of materials and optimization of structural elements. However, in practice, slab type selection is often guided by convention, aesthetics, or short-term cost, with limited attention to soil-related impacts. This can lead to structurally or economically suboptimal choices. Therefore, this study investigates how different slab systems affect building cost under varying soil conditions. In this context, three different soil classes (ZB, ZC, and ZD) were selected in accordance with the Turkish Building Earthquake Code (TBDY 2018). For each soil class, two slab types (Hollow block slabs and slab with beam) were used to model structures, resulting in a total of 18 building models. Static and seismic analyses were conducted using the ideCAD v.11 software, and quantity take-offs for concrete, reinforcement, and formwork were performed. The rough construction costs were calculated based on the 2025 unit price data published by the Ministry of Environment, Urbanization and Climate Change. The analysis results revealed that deterioration in soil class does not always lead to an increase in construction cost. In some scenarios, cost trends varied depending on structural and geotechnical interactions. Furthermore, the comparison between slab types showed that hollow-core slabs were generally more expensive than ribbed slabs. These findings highlight the necessity of considering both soil conditions and slab type selection as integrated parameters in cost-effective and structurally sound building design.