Design and calculation of the load carrying capacity of prestressed concrete columns in greenhouse systems

Prestressed concrete column (PCC) systems, with a broad range of applications, can be used in various environments such as gardens, park areas, and greenhouses, as well as in private land areas like plots and fields, and for long-term applications in electricity poles and lighting fields. Prestressed concrete columns of different sections are produced by providing optimal prestressing to varying numbers, diameters, and winding counts of prestressing steels, along with casting high-strength ready-mixed concrete into vibrated molds. The primary objective is to determine the optimum designs of these columns and ascertain their load-carrying capacities under different load conditions. Prestressed concrete columns are obtained by placing prestressing tendons in lieu of the reinforcement used in regular reinforced concrete columns. In comparison to regular reinforced columns, prestressed columns exhibit economy due to lower weight, enhanced strength, and reduced requirement for reinforcement. The smooth surface of the columns, along with the dense and less permeable structure of the tendons inside, prevents corrosion. Additionally, prestressing the column ensures less displacement and less deformation under applied loads. These columns need to be designed and analyzed under combined axial and bending loads. This thesis work focuses on the design and load-carrying capacity calculation of prestressed concrete columns in greenhouse systems, unfolding in three stages. In the first stages, the design of a prestressed concrete column is explained step by step using a design example, and axial load-moment interaction data and graphs are generated. Information about load-carrying capacities is obtained from the collected data. In the second stage, the fabrication process and loading tests of the prestressed concrete columns given as design examples are carried out. Based on the results obtained from experiments on 24 column samples, an attempt is made to understand the real behavior of these columns. In the third stage of the thesis, the suitability of using prestressed columns in greenhouse structures is extensively examined using a sample greenhouse structure. Moreover, the suitability of using these columns in the intended area is validated by modeling in the SAP2000 structural analysis program. During the design, Türkiye Bina Deprem Yönetmeliği 2018 (TBDY-2018), TS EN 1991-1-3, TS EN 1991-1-4, and European Standards regulations such as EN 13031 and EN 10138-3 are taken into account. When compared to greenhouse systems consisting of steel profiles as structural components, preliminary analyses suggest that considering the concrete quantity depending on the section, the number of prestressed steel tendons applied, formwork construction, and on-site application, the cost can be reduced by more than half. Therefore, developing a design proposal that includes the structural behavior of prestressed reinforced concrete columns will provide economic benefits for new greenhouse and covering systems.