Structural steel is used in construction or building projects. In its most basic definition, structural steel is defined as steel shaped for use in construction, but that doesn’t give a very clear picture of what structural steel actually is. As your premier local structural steel company in Indiana, we wanted to help give you a clearer understanding of what sets structural steel apart from other forms of fabricated steel by covering its two main characteristics: composition and shape.Structural steel is a carbon steel, meaning it has a carbon content of up to 2.1 percent by weight. After iron, carbon is the most important element in carbon steel. Increasing the amount of carbon in the composition of steel results in materials that have high strength and low ductility. Depending on how the steel will be used will determine the carbon level or content needed.