Steel trusses are designed and sized using a combination of engineering principles, computer-aided design software, and industry codes and standards. The design process involves considering the specific requirements of the structure, such as the span, load conditions, and desired aesthetics. Factors like material properties, shape, and member connections are taken into account to ensure the truss can safely support the applied loads while minimizing deflection and stress. The sizing of steel trusses involves optimizing the dimensions and cross-sectional properties of the individual members to achieve the desired strength and stability. This is done by analyzing the internal forces and moments within the truss, often utilizing finite element analysis to accurately model the complex behavior of the structure.