Metal roof provides increased wind resistance when compared to other roofing materials. This is because metal roofing systems use interlocking panels. The disadvantages of metal roofs include the noise created from rain hitting the roof, and, in snowy areas, the tendency of snow to easily fall off the roof and onto pedestrians or property. Originally, metal roofs were made of corrugated galvanized steel: a wrought iron–steel sheet was coated with zinc and then roll-formed into corrugated sheets. Another approach is to blend zinc, aluminum, and silicon-coated steel. These products are sold under various trade names like "Zincalume" or "Galvalume". The surface may
PC strand well as 1720, 1770, 1960, 2000, 2100 MPa and the like intensity levels. The yield strength of this steel is also higher. In most of the post-tensioned and pre-tensioned prestressed project, smooth steel strand is the most widely used prestressed steel. Stranded strand is mainly used to enhance the project, but also for nuclear power and the like works. Galvanized steel strand commonly used in the bridge of the tie rod, cable and external prestressing works. Epoxy coated steel stranded wire is similar to galvanized prestressed steel wire. Countries have standards for prestressed strand, such as: China Standard GB /