The introduction point-type supporting glass structure is a new type of building structure which has been widely used in recent years. The utility model has the advantages of elegant appearance, good permeability and the like. The Beijing Botanical Garden uses the structure of the glass in the greenhouse, and uses the metal connecting member to connect the supporting system and the glass plate into one body in order to reasonably evaluate the bearing performance of the glass room point supporting glass structure. .ç ”ç©¶ Study the bearing capacity of metal connectors.
The gold connector is divided into two parts: a gold fastener and a support member (claw member). The geometrical dimensions of the finite element transverse 9 typical fixed floating head and countersunk fasteners are as shown in the figure. This geometric model divides the mesh to generate a finite element model. Considering the symmetry of the model, only the 1/2 model is established. As shown in the actual project, the screw of the fastener is fastened to the support member to simulate the real In the case, a solid end constraint is applied to the screw end of the model, and a symmetrical constraint is applied to the cross section. Fasteners may be subjected to different loading effects such as pulling, pressing, shearing, shearing and shearing, and compression and shearing. Therefore, loads are applied to different parts of the model to simulate different loads. When the fastener is pulled. An upward compressive stress shall be applied to the lower surface of the upper pad: when the fastener is pressed, a downward compressive stress shall be applied to the upper surface of the lower pad; if the fastener is sheared, the inner shaft shall be Apply a nodal force on one side. The fastener material is made of stainless steel lCrl8Ni9, and the mechanical properties and physical properties of the chamber are calculated only in the online elastic stage.
The finite element type of typical fixed fasteners (a) fixed to the floating head; (b to the countersunk head 2 typical fixed gold fasteners analysis 2.1 fixed floating head fasteners bearing performance when fixed floating head fastening When the piece is subjected to load, it is possible to reach the maximum value of vonMiscs stress at three key points: a. the upper plate and the mast are connected; b. the joint between the mother and the screw: c. the end of the screw. The stress values ​​at these critical points determine the control points for the bearing capacity.
Since the model is only calculated in the online elastic phase, when the fastener is only subjected to tensile force, pressure or shearing force, only the unit force can be applied to the model for analysis without the need to load the w. fixed floating head fastener. The vonMiscs stress values ​​for each key point of the tensile load capacity model are shown in Table 1.
Table 1 Calculated value of vonMiscs stress and theoretical value / MPa stress calculated value of the stress value of the fixed floating head firmware when tensioned, the stress concentration factor 〃c / 1 screw end part of the upper end of the screw and the screw The table at the junction of the mast indicates when the fastener is pulled. The stress concentration of the upper pad and the screw is the most serious. The tensile bearing capacity of the fixed floating head fastener is controlled by the concentrated stress at the joint between the upper pad and the mast. The yield strength of stainless steel is 196N/rranM. Therefore, the tensile load capacity of the fixed floating head fastener is 3.16kN. Calculating the von Mises stress and the theoretical vonMises stress column at various key points of the compression bearing performance model of the fixed floating head fastener In Table 2: Table 2 calculated values ​​of vonMises stress and theoretical value / MPa stress calculation value of each key point when the floating head fastener is pressed. It is known from the calculation results that the tensile load capacity of the fixed floating head fastener is less than solid. The countersunk fastener is attached, and the former has greater compressive and shear bearing capacity than the latter. Therefore, from the standpoint of load bearing performance, if the fastener is used to suspend the glass plate, the countersunk fastener should be used: if it is used to support the glass plate or bear the weight of the wall glass, it should be selected. Floating head fasteners.
The stress concentration factors of the key points given in this paper are only for the general situation of the typical fixed fasteners in the glass greenhouse of Beijing Botanical Garden. It is necessary to further study the factors affecting the stress concentration factor at key points, so formula (1)(9) The value of the stress concentration factor will vary.
The calculation results of the theoretical formula and the finite element analysis also require experimental testing, which is also an in-depth work in the future.
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