中欧温室规范中风荷载取值的对比

为了更好地指导温室结构设计与优化,该文对中欧温室结构规范中风荷载的取值方法进行了比较。首先简要比较了中欧温室规范中风荷载的定义和计算方法,然后分别对2种规范中关于基本风压、风压高度变化系数及结构体型系数的规定进行了详细地探讨。比较结果表明,中欧温室风荷载在计算思路上相近,但在参数的定义及选取方面,中国温室荷载规范存在一些不合理性。该文还根据中欧的不同规定,利用结构分析软件SAP2000对某典型温室进行了风荷载效应的计算对比,结果表明采取欧洲温室规范计算所得的结构内力值更高,并对中国温室荷载规范进一步的修订提出了一些建议。

Comparative study on calculation of wind loads on greenhouse structures between codes of China and Europe

Abstract: Among all the bearing loads for greenhouse structures, wind load plays a leading role and this is especially true for a modern greenhouse structure due to its large-span and lightweight characteristics. As a result, to ensure reliability and a reasonable cost for the design work of greenhouses, wind load becomes a key factor. Since the modern greenhouse started late in China, there was no domestic load specifications for greenhouse structures until 2002 when the national code "Greenhouse Structure Design Load" was published. This code filled in the blanks of this area in China, but its shortcomings are still obvious, as it cannot fully take into consideration all the particularities of a greenhouse structure. Therefore, it is necessary to take advantage of the experiences of advanced countries in greenhouse design and have some research on greenhouse design load codes. In combination with the Chinese Load Code and Eurocode1: Part1-4, this paper conducted a comparative study on the calculation of wind loads on greenhouse structures between the codes of China and Europe. In the first part of this paper, the definitions and calculation methods of wind load were compared briefly between Chinese and European Codes for Greenhouse Structures. Then, more specific discussions were carried out on three main factors: basic wind pressure, wind profile, and wind pressure coefficient. The comparison results showed that the calculation methods of wind load for a greenhouse structure are similar between Chinese and European Codes, but the definition and selection of some parameters are too simplified to be reasonable in the Chinese Codes. Specifically, the comparison study on basic wind pressure shows that the definition of this variable is almost the same in these two codes except that when under certain circumstance, the European greenhouse code takes into consideration its importance and the design working life of the greenhouse. As a result, the basic wind pressure return periods have different choices, while the Chinese Greenhouse Code Unified used the 50-year return period, which does not reflect the characteristics of the greenhouse structure. The result of a comparison study on the wind profile shows that the value of wind profiles in the European codes is greater than that in Chinese codes in that the wind turbulence factor is taken into consideration in the European codes. The comparison study on the wind pressure coefficient shows that the coefficients in European codes are larger than the ones in Chinese codes for the same multi-span greenhouses. In summary, the specifications in the European codes are much more comprehensive than the specifications in Chinese codes. A detailed example is presented to illustrate the overall comparison. According to the different requirements of Chinese and European codes, the wind load effects of a typical Venlo-type greenhouse structure were analyzed using the structural analysis software SAP2000. The results showed that the calculated internal forces are higher when the European greenhouse specifications were applied, though their distribution in the structure is almost the same. At the end of this paper, some suggestions are put forward for the further amendment of the Chinese greenhouse design code in the future.