Final answer:
A U-shape form made of two flanges connected by a common web is known as an I-beam, which is widely used in construction for supporting heavy loads and enabling longer spans without intermediate supports.
Step-by-step explanation:
A U-shape form made of two flanges connected by a common web is commonly known as a I-beam. These beams are frequently used in construction due to their ability to handle a variety of loads and reduce bending strains. An I-beam has two horizontal planes, known as flanges, connected by a vertical component, the web.
The use of I-beams allows a structure to span longer distances and support more weight without the need for intermediate columns or supports. This design is highly efficient in terms of both the material used and the structural support it provides. As depicted in Figure 12.21, steel I-beams have been integral in construction projects for creating a sturdy framework.