The selection of grid structure for grid processing

There are many factors that affect the selection of grid frame, such as the production of grid frame, installation method, steel index, span size, stiffness requirements, plane shape, supporting conditions and so on, which kind of grid frame form is affected to a certain extent.

1. If the nodes are welded, the grid composed of plane truss system is more convenient than the grid composed of four-angle cones; Two - way orthogonal grid is more convenient than two - way oblique grid and three - way grid. Quadrangular cone mesh is more convenient than triangular cone mesh.

2. The installation method does not adopt overall lifting or lifting, but adopts strip or block installation, or when using the high-altitude sliding method, it is more conducive to choose three kinds of orthogonal and orthogonal vertical lattice, namely two-way orthogonal vertical lattice, vertical square pyramid lattice, vertical square pyramid lattice with evacuation time, etc.

3, the steel index is an important symbol to measure the selection of grid.

4. The calculation shows that the span size has little influence on the selection of grid structure. However, large span grid structures are often important buildings. At present, grid structures composed of planar grid systems such as bidirectional orthogonal grid structure, bidirectional orthogonal grid structure, and three-directional grid structure are widely used in China. Because this kind of large-span grid structure design and construction experience is rich and skilled. Three-way grid, tri-cone grid, hexagonal cone grid, the general structure is more complex, need to use large amount of steel, small and medium span should be used less.

5. The stiffness of the truss is much better than that of the plane roof truss, but the difference between all kinds of truss, whether horizontal stiffness or vertical stiffness, is not small. If diagonal quadrangular cone mesh frame, it itself is geometrically variable, in addition to edge members or a strong ring beam to ensure its geometric invariance. Generally speaking, the number of nodes and the number of bars is more, such as trigonal cone mesh, hexagonal cone mesh, three-way mesh, is put quadrangular cone mesh, the stiffness is larger; On the contrary, such as diagonal quadrangular cone grid, checkerboard quadrangular cone grid, evacuated triangular cone grid I, II, honeycomb triangular cone grid, the number of nodes and rod to the less, the stiffness is smaller.

6, the plane shape has circle, regular hexagon and nearly circular polygon mesh. From the point of view of plane layout and architectural modeling, three-dimensional grid, hexagonal cone grid, triangular cone grid, vacuumed triangular dimension grid I, II and honeycomb triangular cone grid are more suitable. Especially when the plane shape is a regular hexagon, these grid structures have regular grid, few types of rods and are convenient for construction. If other types of grid structures are used, the grid near the boundary will be irregular and disorderly, the types of bars will increase, and the construction will be inconvenient.

7. For multi-point support grid structure, orthogonal vertical grid structure is more suitable. The mechanical properties of the multi-point supported orthogonal mesh structure are more reasonable and the deflection is smaller than that of the inclined mesh structure. The calculation of four-point support support grid shows that under the same conditions, the ratio of internal force and deflection of bidirectional orthgonal grid and bidirectional orthogonal DIAGONAL grid IS about 5/7 and 6/7, respectively. In addition, diagonal mesh also needs to add edge strips on the free boundary, which increases the number of strips and the amount of material. The net frame with three supports and one opening should also be orthogonal and upright. The mesh frame with the combination of peripheral support and multi-point support can use orthogonal forward type mesh frame or oblique type mesh frame, but generally it is not suitable to use the mesh frame composed of three-way mesh frame and triangular cone and hexagonal cone.

8, for the span of the multi-storey building floor is not greater than 40m and the span of the roof is not greater than 60m, reinforced concrete slab can be used instead of steel chord rod combination grid. The qualified network shall be composed of square pyramid group qualified network, square pyramid group qualified network, two-way orthogonal square pyramid group qualified network, oblique square pyramid group qualified network and honeycomb triangle pyramid group qualified network.