6　Structure of Ducts

6.1　General Requirements

6.1.1　Ducts and their support members shall be designed to have sufficient strength，rigidity and stability to avoid any intense vibration，and shall be cost effective，safe and easy for fabrication.

6.1.2　The design load for the ducts shall be the combination of the following loads：

a）Internal pressure load-the design fluid pressure（positive or negative）；

b）Gravity load-the weight of the ducts（including ducts，reinforcement ribs，components and parts，and insulation）；

c）Additional load-the wind load，snow load and the weight of accumulated deposit；

d）The weight of platform and the live load on platform shall be included，if platform is required.

6.1.3　All openings and joints in ducts and stack shall be air-tight.