# Research on Snow Load Characteristics on a Complex Long-Span Root Based on Snow-Wind Tunnel Tests
## 3 Experimental Research on Snowdrifts on Complex Long-Span Roof  
### Experimental Setup  
#### 3.1.1 Test Model  
For buildings with a special shape, complex separation and reattachment occur when airflow passes over the roof. The snow load on the roof will be redistributed easily, which may change the stress inside the roof structures, thereby leading to building collapse, especially for long-span lightweight roofs. Therefore, significant attention should be paid to the snow distribution on complex-shaped buildings. Based on the advantages of the experimental method and the validated similarity criterion, a series of snow-wind tunnel tests were conducted to investigate the snowdrift on such complex long-span roofs. In this study, Tongren Olympic Sports Center Stadium was selected as the target building. As the stadium is located on the Yunnan-Guizhou Plateau, China, the frequent snowfall requires additional consideration. The geometric shape of the roof is illustrated in Figure 5a. The cable membrane structure was adopted for the prototype roof. In order to avoid the excessive deformation of the roof, which may affect the safety of the structure and comfortableness of the space, the roof deformation should be strictly controlled at the structural design stage. Therefore, the roof deformation under the action of snow load was assumed to be negligible. Furthermore, considering that the unique roof shape substantially affects the shape of the snow cover, acrylonitrile butadiene styrene (ABS) plastic was used for creating the model roof to reproduce the complex shape as far as possible. Similar  
Figure 4: Comparison of horizontal distributions of normalized snow depths: (**a**) prototype result [18]; (**b**) experimental result.  
hard material was also used by [PERSON] et al. [13] to make the membrane structure models. Perforated plates were adopted for the sidewall, with an air permeability of approximately 40% to realize the simulation of the wall air permeability (Figure 5b). Based on the above conclusion, the model scale of 1/150 was selected with model size limited to 1.81 (x) \(\times\) 1.69 (y)0.33 \(\times\) (z) m.  
The measuring points were designed according to the special shape of the roof (Figure 6a), combined with the distribution characteristics whereby snow would be deposited in the concave region more easily. Two types of concave regions were formed on the roof: along the radial cable and near the center of each membrane piece. For the concaves along the radial cables, 36 lines were set along the cables, with 16 measuring points set along each line (Figure 6b). For the concaves formed on the membrane, 36 lines were set along the circumferential direction, with an additional 9 measuring points set at the center of each membrane piece (Figure 6b). In total, 900 measuring points were set on the model roof. The snow depth at the measuring point was measured with a snow stick. Furthermore, a snowdrift experiment with an empty field was conducted to simulate the snow distribution on the ground. The shape coefficient \(\mu\) of the snow distribution on the roof was calculated as the ratio of the snow depth on the model roof to the snow height on the ground.  
Figure 5: Model of membrane structure gymnasium: (**a**) Tongren Olympic Sports Center Stadium model (made of acrylonitrile butadiene styrene (ABS) plastic); (**b**) wall of membrane structure (40% air permeability).  
Figure 6: Arrangement of measuring points for snow depth: (**a**) roof form; (**b**) arrangement of measuring points.