What is an engineered I-beam primarily composed of?

An engineered I-beam is primarily composed of wooden upper and lower chords with a web of oriented strand board (OSB). This design is utilized because it combines the strength and flexibility of wood with the engineered properties of OSB, creating a beam that is both lightweight and structurally sound. The wooden chords bear the compressive and tensile loads, while the OSB web provides stability and resistance to shear forces. This construction method allows I-beams to span greater distances than traditional solid lumber beams, making them an efficient choice in building construction.

In contrast, other materials listed in the choices do not typically form the structure of engineered I-beams. Options that reference plastic, steel, or concrete suggest different engineering principles and constructions, which are more common in other types of structural components. Therefore, the composition of wooden chords with an OSB web is what sets the engineered I-beam apart, making option B the most accurate.