The joist is a piece made of steel and concrete, with the blocks placed on it as molded concrete (molded in place) to form an appropriate T-section.
Truss joists are of two types:
Clay with durable form (clay) called shavings.
Joist without durable mold (concrete)
The truss joist is made of steel truss and concrete heel. The truss joist is a prefabricated bottom and transverse (zigzag) truss rod that is welded or hooked together to provide the necessary support for the carriage and its components. they do.