Innovative models for optimizing steel formwork weight in concrete column construction: A case study

• Two models were developed to minimize steel formwork weight for concrete columns. • The developed models achieved formwork weight reductions of more than 25%. • Sheathing thickness and beam size greatly impact formwork weight. • Findings support designing for full pressure, allowing flexible casting rates. This study examines the optimization of steel formwork weight for concrete columns, focusing on key decision variables: sheathing thickness, beam cross-sectional size, and beam spacing. Two optimization models were developed using a genetic algorithm. The first divides the column into equal-height sections and calculates beam spans based on the maximum lateral pressure in each section. The second allows variable beam spacing along the column height to reflect pressure variations. This research also aims to determine whether formwork should be designed to withstand full hydrostatic pressure, thereby eliminating the need for contractors on-site to adjust casting data to suit the formwork. A sensitivity analysis on the decision variables was conducted. A case study of a 5.9 m-high column (baseline formwork mass 2,890 kg) illustrates the models’ benefits. In the original project, the contractor had to significantly reduce the intended one-hour casting rate because the existing formwork would have collapsed at that rate. Using the same reduced casting rate, Model 1 and Model 2 reduced formwork weight by 27% and 29%, respectively. When the formwork was designed to resist full hydrostatic pressure, allowing any casting rate, Model 1 and Model 2 achieved reductions of 17% and 22%, respectively. Sensitivity analysis showed that sheathing thickness and beam cross-section size are very influential variables. Furthermore, designing formwork to withstand full hydrostatic pressure using the developed models yields lower weight than the traditional design with constant beam spacing and a reasonable casting rate. Therefore, the findings support adopting full-pressure design in practice.