## 3 Load Analysis of Photovoltaic Support  
### Load Calculation  
Based on design information and on-site observations, the loads acting on photovoltaic supports primarily include the weight of the photovoltaic panels, the wind load, the snow load, and the construction load. Additionally, the Chinese code NB/T 10115-2018 [32]  
Figure 5: Photos of typical support damage. (**a**) Bending occurs at the upper end of the brace. (**b**) Bending occurs at the lower end of the brace. (**c**) The surface of the photovoltaic panel is uneven. (**d**) Two bolts used at the purlin hanger to connect the purlin and beam. (**e**) Three bolts used at the purlin hanger to connect the purlin and beam. mandates the consideration of the longitudinal wind load on photovoltaic supports. The load calculation method is given as follows:  
1. Weight of photovoltaic panels  
Based on specific design parameters, the dimensions of the photovoltaic module were 2285 mm \(\times\) 1134 mm, with a thickness of 35 mm. The weight of the single module was calculated to be 31.6 kg. The self-weight of a single photovoltaic module was determined using the formula \(G=mg\) where \(m=31.6\) kg and \(g=9.8\) m/s\({}^{2}\), yielding \(G=31.6\times 9.8/1000=0.310\) kN. 2. Wind load  
Wind load is a critical external factor that significantly influences the mechanical stress distribution and structural integrity of photovoltaic support systems [33]. As shown in Equations (1)-(3), the theory of the wind load calculation in Chinese codes, American codes, and Eurocodes is largely similar [34], involving the determination of reference wind pressure based on the basic wind speed and subsequent adjustments to account for factors such as structural dynamic response, topography, terrain roughness, and others. \(\beta_{\text{z}}\) in Equation (1), \(G\) in Equation (2), and \(c_{\text{d}}\) in Equation (3) all represent the impact of wind pressure pulsation on structures. \(\mu_{\text{s}}\) in Equation (1), \(K_{\text{d}}\) in Equation (2), and \(c_{\text{f}}\) in Equation (3) represent the influence of wind direction on structures. \[\omega_{k}=\beta_{\text{z}}\mu_{\text{s}}\mu_{\text{z}}\omega_{0} \tag{1}\]  
Here, \(\beta_{\text{z}}\) is the gust-effect factor, \(\mu_{\text{s}}\) is the shape coefficient of the photovoltaic module, and \(\mu_{\text{z}}\) is the height variation coefficient of wind pressure. \[p=q_{h}K_{\text{d}}GC_{N} \tag{2}\]  
Here, \(q_{\text{h}}\) is the velocity pressure evaluated at the mean roof height, \(q_{h}=0.613K_{\text{z}}K_{\text{z}t}K_{\text{t}}V_{\text{3}\text{z}}^{2}\), \(K_{\text{d}}\) is the wind directionality factor, \(G\) is the gust-effect factor, and \(C_{\text{N}}\) is the net pressure coefficient. \[\omega=c_{\text{s}}c_{\text{d}}c_{\text{f}}q_{\text{p}} \tag{3}\]  
where \(c_{\text{s}}\) is the size factor, \(c_{\text{d}}\) is the dynamic factor, \(c_{\text{f}}\) is the force coefficient, and \(q_{\text{p}}\) is the peak velocity pressure. However, the value of the influence coefficient varies among codes. In the Chinese code, the basic wind speed (\(V_{\text{10 min}}\)) is defined as the average wind speed measured at a height of 10 m above open, flat ground in the local area. The Eurocode shares a similar definition. In contrast, the basic wind speed (\(V_{\text{3s}}\)) in ASCE7-10 refers to the gust wind speed corresponding to a 3 s return period at a height of 10 m in a Class C site, with an approximate ratio of \(V_{\text{3s}}/V_{\text{10 min}}=1.42\text{:}1\)[15]. Although the basic wind speed is relatively high, the gust-effect factor \(G\) in ASCE7-10 is 0.85, which is smaller than that in [23] GB 50009-2012. The directional influence coefficient in BS EN 1991-1-4 is relatively large, while it is the smallest in NB/T 10115-2018. Additionally, it is noteworthy that in load combination analysis, the partial coefficient of the wind load is 1.0 in ASCE7-10, 1.4 in the Chinese codes [30], and 1.5 in BS EN 1991-1-4 [21].