## 1 Introduction  
The large-span roof structure has many advantages such as various external forms and briefing, resulting in its wide application and often as a local landmark building. It is also the practice of this type of architecture that promotes the innovation and development of spatial structures. The large-span roof structure has the characteristics of light weight, large flexibility, small damping, low natural vibration frequency, and dense mode shapes, and its main mode shapes are not concentrated in the first few orders like high-rise buildings, which makes it more sensitive to the effect of wind. Cases of wind-induced disasters caused by excessive wind force are not uncommon [1; 2; 3; 4]. Therefore, it is of great significance to reasonably and effectively predict the wind load of the large-span roof structure to improve its wind resistance performance. Due to the large spatial span of the large-span roof structure, there are often more effects such as vortex shedding and reattachment, the quasi-steady theory is no longer applicable, and the wind load is very complex [5; 6; 7]. Furthermore, due to its complex and diverse structural forms, neither the norm nor the design guideline can provide universal wind load calculation parameters such as body shape coefficient, which often need to be obtained through means like field measurement, numerical simulation, and wind tunnel test [8; 9; 10; 11; 12]. However, field measurement is rarely used because it has significant limitations such as being time-consuming and labor-consuming and having expensive and harsh conditions. Although numerical simulation has the advantages of low cost, short period, and few restrictions, the current method still has obvious difficulties in grid division, turbulence modeling, and computational efficiency, and the accuracy cannot be guaranteed, so it is not widely used. As an irreplaceable method in aerodynamic research, the wind tunnel test is the most common and effective method to obtain parameters such as body shape coefficient of large-span roof structure. Unfortunately, due to the limitations of the model and test conditions, the number of wind pressure measurement points in the test is very limited, and it is far from being able to accurately evaluate and predict the wind load of large-span roof structures. Therefore, it is very important to obtain the wind pressure information in the area without pressure measuring points more accurately and conveniently. At present, there are two conventional methods: one is to use the test results at the nearest measuring point as the wind load time history in the unknown area; the other is to increase the density of test results on the measuring points by spatial interpolation to obtain wind load time history data in the unknown areas. The former is obviously unreasonable. For the latter one, based on the limited wind tunnel test pressure measurement data, how to select a reasonable and effective processing method to improve the test data utilization rate and the wind load evaluation accuracy of large-span roof structures has become an urgent problem. As a mathematical tool to analyze the statistical characteristics of complex random fields, the method of proper orthogonal decomposition (i.e., POD, also known as the Karhunen-Loeve expansion) has been widely used in many fields [13; 14; 15; 16; 17]. In the field of stochastic wind field, the stochastic phenomenon is simplified by adopting the space-time separation technique in a new coordinate space, and the wind pressure field is decomposed into a series expansion of principal coordinates only related to time and eigenmodes only related to space. The eigenmodes at the points to be evaluated are predicted using a spatial interpolation method. Then combine them with the principal coordinates, and the wind pressure field can be approximately described with finite terms to simplify the distribution of the wind pressure field for simplified analysis.