Influence of greenhouse's shape in the structural performance

The aspects of structural safety in greenhouses are directly related to the design of their structure and functionality. The diversity of shapes of such rural constructions, with their required design characteristics, provides different efforts in the structural elements, as well as different internal volumes. In this study, the stress distribution in the structural elements was evaluated in relation to variations in the shape of pitched roof greenhouses. For each evaluated shape, the variables were defined according to the parameters of Eurocode EN 13031-1. The shapes analyzed were established considering the ratio between height and span (0.3 and 0.6), roof slope (20 and 26°) and internal and external pressure coefficients. Two groups, A and B, were divided by the size of the spans, 6.4 and 8.0 m, respectively. Thereby, eight cases were calculated by the Finite Element Method (Ansys^©), with the zones of columns and roofs discretized by the element type Beam44. The maximum stresses obtained by the element for each load (dead load, live load and wind load) were combined in the Ultimate Limit State. In both groups (A and B), by varying the roof slope from 20 to 26°, it was noted that the maximum stress in the roof elements decreased of up 20% and increased in the column elements up to 57%. The variation of the ratio of height/span from 0.3 to 0.6 caused an increase of up 66% in the maximum stresses of the columns and 47% in the roof zones. This study revealed that there is a strong relationship between the stress distributions, due to the variations imposed on the greenhouse shape.