Abstract: Abstract： It is not easy to directly test the wind loads on small components using wind tunnel test of scale model. Therefore, the technology of numerical wind tunnel was used. By the establishment of the building and the space model of its roof purlins, and by dividing local grid refinement, the wind load distribution on the purlins of open roofs was obtained at different wind angles. The results show that when subjected to skew wind, the open purlins are more unfavorable, and the horizontal shear force is more significant than the vertical suction, which is an important part of wind load calculation. The wind load distribution on the purlins has obvious regularity. First, in the cusp region of the roof, the wind load is the largest since the roof curvature is the maximum, and the air flow produces a strong separation of convection to form a strong vertical suction and horizontal shear wind force. Second, in the outer area of the roof, the wind load is large too, which is directly related to the air separation from the architecture marginal zone. Finally, in the inner area of the roof, the wind load is significantly smaller and more uniform. By closing the bottom of the purlin, the extreme wind load on the outer area of the roof can be effectively reduced by more than 20%, but it does not have obvious effect on the inner area of the roof. It is recommended that the initial design, the bottom of the purlin should be closed only at the edge of the roof.

Key words: metal roofing, open purlins, wind load distribution, numerical wind tunnel, aerodynamic measure