# Fatigue Analysis of Greenhouse Structure under Wind Load and Self-Weight
## 1 Introduction  
In recent years, the greenhouse structures used in horticulture facilities have become larger and lighter. Climate is changing rapidly owing to global warming, and the damage caused by wind, heavy snow, and heavy rain is increasing. Several researchers are investigating the stability of greenhouse structures. [PERSON] et al. calculated wind load at the maximum wind speed, performed structural analysis using the wind load factor according to the standards of Brazil and the EU (European Union), and they evaluated stability by considering the moment and maximum stress distribution in columns [1]. [PERSON] et al. conducted an analytical investigation using the optimal design technique [2;3]. [PERSON] compared wind loads according to the standards of Europe and China and compared the stress distribution of main materials with respect to static load [4]. In addition, [PERSON] evaluated the wind load on greenhouses, in addition to their structural stability [5]. Furthermore, [PERSON] et al. investigated wind load for the stability design of a duo-pitch-shaped greenhouse [6]. [PERSON] et al. examined the structural and functional characteristics of greenhouses based on the design requirements of the EU [7]. [PERSON] et al. applied wind load and evaluated the frame stress of various structural forms of the single-span pitch roof type to evaluate the effect of pressure coefficients according to European standards and the Brazilian standard ABNT [1]. [PERSON] et al. analyzed the wind profile to calculate the wind pressure of a greenhouse to study the characteristics of wind speed [8]. [PERSON] et al. investigated the wind speed distribution in South Korea. In particular,Camilo [PERSON] et al. investigated the determination of the Weibull parameter for wind energy [9]. [PERSON] et al. conducted a study on the classification and distribution of wind speed and on the wind spectrum [10]. The fatigue analysis for wind load was also carried out in various ways [11]. [PERSON] et al. conducted a wind-induced fatigue analysis of high-rise steel structures using an equivalent structural stress method [12]. In addition, [PERSON] et al. have been studying the fatigue analysis by applying thermodynamic theory, but it is still difficult to apply to complex objects. Therefore, in this study, the existing fatigue analysis method is applied and analyzed [13; 14; 15; 16]. However, these studies in greenhouses did not reflect the characteristics of wind load for a simple model or the dynamic characteristics of wind load as a method of evaluating the maximum stress of frame. They only compared the degree of the experiment and analysis of wind pressure coefficients and evaluated the appropriateness of applying the result to the design of wind load, or evaluated the maximum stress of the frame at the maximum wind speed through static structural analysis of a simple model. These studies were conducted for only one dynamic load or one static load. No study has been conducted yet on the stability of a structure due to the complex loads in which both dynamic loads and static loads are simultaneously applied--such as wind and self-weight--to a detailed model of the structure. In this study, the changes in the stress distribution of structures were examined under a combination of self-weight and wind loads, and fatigue life was predicted by creating time series data for wind speed through the random generation of the Weibull distribution. The wind pressure on the exterior of a greenhouse was calculated through fluid dynamics analysis and applied as wind load. Furthermore, for the stress model of fatigue analysis, stress, which was obtained through structural analysis based on wind load, was normalized by the square of wind speed. Various analyses were performed for investigating the effectiveness of self-weight, including the compensation of fatigue estimation stress and neglecting self-weight. An appropriate fatigue analysis methodology was proposed by comparing the fatigue analysis results with those of the stress-normalized model.