Grid structure system
Spatial structure is composed of a plurality of rod according to certain grid form by a node link a. It has advantages in space force, light weight, high stiffness, good seismic performance; used as a gymnasium, cinema, exhibition hall, waiting hall, the roof of the stadium bleachers awning, hangar, two-way large column from the workshop building. The disadvantage is the number of rod more converge on the node, making installation more complex plane structure.
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The grid structure according to the different shape, can be divided into double plate type truss structure, single and double shell type truss structure. Plate type truss and double shell type truss element is divided into upper chord, the bottom chord and web members, mainly bear tension and stress; the single shell type rack bar, in addition to bear tension and pressure, but also under bending moment and shear. At present, the grid structure of China by the vast majority of the plate type truss structure.
Grid structure plate grid structure according to the form of composition is mainly divided into three categories: the first category is composed of plane truss, two to the orthogonal space truss, two to the orthogonal diagonal grid, two oblique crossing grid and grid obliquely placed three to four forms; the second class is composed of four pyramidal cell, there is four pyramid space grids, is putting evacuated four pyramid space grids, oblique four square pyramid space grid, the board five form four pyramid space grids and star four pyramid space grids; third class composed of triangular pyramidal cell, triangular cone net frame, evacuating the triangular pyramid space grid and honeycomb shaped triangular pyramid space grid in three forms. Shell type grid structure according to the shell surface form mainly cylindrical shell type rack, spherical shell type grid and hyperbolic paraboloid shell type space truss. The grid structure and the materials are steel truss reinforced concrete truss, and the composition of steel and reinforced concrete composite space truss steel truss, which used more.
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The grid structure is statically indeterminate structure system. Plate type truss analysis, node is generally assumed to be hinged, the external load according to static equivalent principle role in the node, according to the space truss displacement method, namely the hinge bar system finite element method to calculate. Also can use the simplified calculation method, such as cross beam differential analysis method, the pseudo plate method for the internal force, displacement calculation. The single shell type grid nodes typically assumed as rigid, should according to rigid rod system finite element method to calculate; double shell type grid according to hinged truss finite element method calculation. Single and double shell frame also can use the simplified calculation method of quasi shell.
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Cross section of members of truss structure should be determined according to the strength and stability. Increasing the stability of calculation length decreases pressure rod, can be subdivided by adding rod and a support rod and other measures. Node plate type truss steel production and double shell type net frame, the main welding hollow ball node and the bolt ball node three types of nodes, cross board. Grid structure cross board node is suitable for the type member, member and joint plate connected by welding or high strength bolt connection. The grid structure with bolt sphere joints of hollow ball node and is suitable for steel bar. The single shell type grid nodes should be able to withstand the bending internal force, in general, steel consumption accounted for the entire steel frame node structure with steel quantity is 15 ~ 20%.
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Method of construction and installation of the truss structure is divided into two categories: one category is the rise in the overall ground assembly method, the top integral hoisting method and integral lifting method;
