Xinjiang local grid

Xinjiang’s local grid is a spatial structure composed of multiple rods connected through nodes in a certain grid form.

The basic units that constitute the Urumqi grid include triangular pyramids, triangular prisms, cubes, truncated quadrangular pyramids, etc. These basic units can be combined into planar shapes such as triangles, quadrilaterals, hexagons, circles or any other shapes. It has the advantages of space stress, light weight, high stiffness and good seismic resistance; it can be used as the roof of stadiums, theaters, exhibition halls, waiting halls, stadium stand awnings, aircraft hangars, two-way large column grid structures, workshops and other buildings. The disadvantage is that there are a large number of rods that meet at the nodes, and the production and installation are more complicated than a flat structure.

Classification

Different appearance

It can be divided into double-layer plate grid structure, single-layer and double-layer shell grid structure. The rods of plate type grids and double-layer shell type grids are divided into upper chords, lower chords and web poles, which mainly bear tension and pressure; the poles of single-layer shell type grids, in addition to bearing tension and pressure, also bear bending moments and shear forces. Most of the local grid structures in Xinjiang adopt plate grid structures.

Composition form

The first type is composed of a plane truss system, which has four forms: two-way orthogonal Xinjiang local grid, two-way orthogonal oblique grid, two-way oblique grid and three-way grid.

The second type is composed of quadrangular pyramid units, and has five forms: square pyramid grid, square pyramid grid, evacuated quadrangular grid, oblique pyramid grid, checkerboard-shaped quadrangular pyramid grid, and star-shaped quadrangular pyramid grid.

The third category is composed of triangular pyramid units, and has three forms: triangular pyramid grid, evacuated triangular pyramid grid, and honeycomb triangular pyramid grid. According to the shell form, the shell grid structure mainly includes cylindrical shell grid, spherical shell grid and hyperbolic parabolic shell grid. According to the materials used, grid structures are divided into steel grids, reinforced concrete grids and combined grids composed of steel and reinforced concrete. Among them, steel grids are used more frequently.

Internal force analysis

The spherical grid structure is a high-order statically indeterminate structural system. When analyzing the plate-type Xinjiang local grid, it is generally assumed that the nodes are hinged, and the external load is acted on the nodes according to the static equivalent principle. The calculation can be carried out according to the space truss displacement method, that is, the finite element method of the articulated rod system. Simplified calculation methods, such as the differential analysis method of cross-beam systems and the pseudo-plate method, can also be used to calculate internal forces and displacements. The nodes of single-layer shell grids are generally assumed to be rigidly connected and should be calculated according to the finite element method of rigidly connected rod systems; the double-layer shell grid can be calculated according to the finite element method of articulated rod systems. The pseudo-shell method can also be used to simplify calculations for single-layer and double-layer shell grids.