Mechanical properties of column foot bolt joints in Venlo greenhouse

This study aims to clarify the influence of column foot joint size on the joint bearing capacity. Taking a Venlo greenhouse project in Zhuhai as the case, a systematic analysis was first implemented on the characteristic internal force of steel column foot. The center column foot joint was subjected to the axial tensile bending under wind load, due to the bending moment and shear force. The side column foot joint was mainly using axial tensile force, and subjected to axial tensile shear under wind load. Secondly, an optimal design was made on the column foot joint of the center and side column, according to "Code for Design of Concrete Structure", "Regulations for Design of Chemical Equipment Foundation", and "Manual of Concrete Structure". The edge distance of the anchor bolt for the column foot joint of the center column was 100 to 150 mm. The edge distance of the anchor bolt at the foot joint of the side column was 125 to 200 mm. Finally, the bending resistance to the foot joint of the center column, the shear resistance to the foot joint of the side column, and the failure mechanism were studied by numerical simulation and experiment. The results show that the failure of the center and side column was divided into the elastic, yield and ultimate bearing capacity stages. The yield point determined by the apogee accurately represented the moment, as the joint stiffness changed. The yield load and ultimate load of the three kinds of joint decreased with the reduction of the joint structure, the yield load of the central foundation short column joint decreased by about 10% per stage, and the ultimate load decreased by about 7% per stage. Once the edge distance of the anchor bolt in the side column joint was reduced by 25 mm, the two loads were reduced by about 20%. The failure mode of the central foundation short column joint was the concrete conical failure on the tension side. The failure mode of the side column joint was that the concrete wedge was pushed out. The diameter of the anchor bolt posed the greatest influence on the bearing capacity of the two joints under different structures, both of which were more than 15%. There was a small influence of the shear connector on the central foundation short column joint. The influence on the side column joint was less than 10%, due to the different load types. The smaller the sizes of the two joints were, the less outstanding the influence was. The thickness of the bottom plate shared the greater influence on the stiffness of the center column node and the lesser influence on the side column node. The shear connector had the lesser influence on the bearing capacity of the center column node and a greater influence on the bearing capacity of the side column node. The design requirements of embedded parts in “Code for Design of Concrete Structures” can fully meet the bearing capacity requirements of column foot bolt joints of greenhouse structures to resist horizontal forces, indicating the large bearing capacity reserve. The finite element modeling can be used to accurately simulate the mechanical properties and failure of the anchor bolt joint. The finding can also provide a strong reference to design the anchor bolt joint of multi-span columns in the greenhouse.