To enable the combined space frame structure to work together, the key lies in the connection structure of the winding nodes. According to the force characteristics of the upper chord and the ribs, under normal circumstances, the connection between the upper chord node and each member in the upper chord plane is required to be rigid in order to transmit the axial force and the luan moment. However, since the web members of the combined space frame structure are the same as the general web members and only bear axial force, the connection between the web members and the upper chord node can still be a fine connection.
Therefore, the upper chord node of the combined space frame structure can be regarded as a kind of semi-rigid and half twisted joint that is rigidly connected in the upper chord plane and circumscribes the upper chord plane. The upper chord node structure of the combined space frame structure is adapted to meet the following requirements:
(1) It must be ensured that the reinforced concrete ribbed slab and the web and lower chord of the space frame can work together;
(2) The axis of the web rod and the central axis of the effective wearing surface of the ribbed plate as the upper chord should intersect at one point at the node:
(3) The gusset plate supporting the reinforced concrete ribbed slab should effectively transmit the horizontal shear force.
According to engineering practice experience and experimental research results, the upper chord nodes of the combined space frame structure mainly have the following types:
(1) Weld the cross plate node. The welded cross plate node is developed from the cross plate node of the general steel space frame, and is mainly used for the angle steel composite space frame structure.
(2) Welded ball missing node. The welded ball joint is formed by welding the stamped ball joint and the steel cover plate, and the ball joint usually uses a small hemisphere. It has the characteristics of high rigidity, simple processing and manufacturing, and strong connection direction of web rods.
(3) Bolt ring node-this is the upper chord joint steel used for the combined space frame structure that has passed the test, trial production and engineering application in our country. The 45 key is selected. The web can still pass through the high-strength bolt and the bottom chord bolt ball joint.
The factory adopts a reliable welding process to weld a round copper plate of Q235 steel on the bolt ring in advance, so that the winding prefabricated plate can be placed and the Q235 steel embedded copper plate of the prefabricated plate can be welded on-site, and the round steel plate can be adjusted at the same time to reduce the size of the bolt ring and the amount of steel used, and enhance the stiffness of the bolt ring.