1 General provisions
1.0.1 This specification is developed with a view to achieving advanced technology, economy and rationality, safety and applicability, and ensuring the quality in the design and construction of the grid structure.
1.0.2 This specification is applicable to the flat type grid structures of industrial and civil building roof and floor (hereinafter referred to as the grid structure), where the roof span should not be greater than 120m, and the floor span should not be greater than 40m.
1.0.3 This specification is compiled in accordance with GBJ 68-84 Unified standards for the design of structures, GBJ 83-85 Design of structures-general symbols units of measurement and basic terms, GBJ 9-87 Building constructions-specifications for loads of architectural structures, GBJ 11-89 Specifications for antiseismic construction design, GBJ 17-88 Specifications for the design of steel structures, GBJ 18-87 Technical specifications for cold shaped thin-walled steel section structures and GBJ 205 Code for acceptance of construction quality of steel structures in combination with the characteristics of the grid structure. In the design and construction, it shall comply with the requirements of this Specification, as well as those specified in JGJ 78-91 Criteria for evaluation of grid constructional engineering quality inspection and other relevant specifications.
1.0.4 The grid structure subject to high temperature or strong corrosion and having fire protection requirements, or the floor grid structure subject to dynamic load shall comply with the requirements of the current relevant special codes or specifications. For the grid structure that directly bears the suspension crane load of medium or heavy working system and needs to be subjected to fatigue test, the fatigue strength and construction shall be determined by special test.
1.0.5 The selection and construction of the grid shall take into account the material supply and construction conditions and production and installation methods in order to achieve good technical and economic results. The specifications and types of members and joints in the grid structure should be reduced to facilitate the production and installation.
2 General requirements of design
2.0.1 The following common forms (Annex I) may be selected as the grid structure:
I. Two-way orthogonal rectangular grid, two-way orthogonal diagonal grid, two-way diagonal diagonal grid, three-way grid and one-way broken-line grid composed of plane truss system.
II. Rectangular square pyramid grid, rectangular square pyramid grid with rods removed, tessellated square pyramid grid, diagonal square pyramid grid and star square pyramid grid composed of square pyramids.
III. Triangular pyramid grid, triangular pyramid grid with rods removed, and honeycombed triangular pyramid grid composed of triangular pyramids.
2.0.2 The selection of the grid shall be determined through comprehensive analysis in combination with the project plane form and span size, support, load size, roof construction, architectural design and other requirements. The grid members must be so arranged that there is no structural geometric variation.
Note: The division of large, medium and small spans in this Specification is in allusion to the roof; large span is more than 60m; medium span is 30m ~ 60m; small span is below 30m.
2.0.3 If the side-to-length ratio (long side/short side) of grid supported along four edges with the plane form being rectangular is less than or equal to 1.5, the diagonal square pyramid grid, tessellated square pyramid grid, rectangular square pyramid grid with rods removed, two-way orthogonal diagonal grid, two-way orthogonal rectangular grid and rectangular square pyramid grid should be selected. For those with small or medium span, the star square pyramid grid and honeycombed triangular pyramid grid may also be selected. If the building requires unequal support distances in both directions of length and width, two-way diagonal diagonal grid may be selected.
2.0.4 If the side-to-length ratio of grid supported along four edges with the plane form being rectangular is greater than 1.5, it is appropriate to select two-way orthogonal rectangular grid, rectangular square pyramid grid or rectangular square pyramid grid with rods removed. If the side-to-length ratio is less than 2, the diagonal square pyramid grid may also be selected. If the plane is long and narrow, one-way broken-line grid may be selected.
2.0.5 For the grid with the plane form being rectangular, supported along three edges and with one edge open, the selection may be conducted according to 2.0.3, and the measures of increasing the number of grid layers or appropriately increasing the height of the whole grid may be taken for its open edge so that the open edge forms vertical or inclined side truss.
2.0.6 For the grid with plane form being rectangular and supported at multi-point, rectangular square pyramid grid, rectangular square pyramid grid with rods removed or two-way orthogonal rectangular grid may be selected according to the specific situation. For multi-span grid supported at multi-point and along edges, two-way orthogonal diagonal grid or diagonal square pyramid grid may also be selected.
2.0.7 For the grid supported along four edges with plane form being round, hexagonal or close to hexagonal, three-way grid, triangular pyramid grid or triangular pyramid grid with rods removed may be selected according to the specific situation. For those with small or medium span, the honeycombed triangular pyramid grid may also be selected.
2.0.8 For multi-storey building floors with the span not more than 40m and roofs with the span not more than 60m, composite grid structure with the upper chord replaced by reinforced concrete slab may be selected. The rectangular square pyramid grid, rectangular square pyramid grid with rods removed, two-way orthogonal rectangular grid, diagonal square pyramid grid or honeycombed triangular pyramid grid should be selected as the composite grid.
2.0.9 The grid may be supported by upper or lower chord; if it is supported by lower chord, vertical or inclined side truss shall be formed at the bearing side.
2.0.10 The grid size and height of the grid may be determined based on the grid form, span size, roof material as well as construction requirements and building functions. The following types of grids supported along four edges may be selected according to Table 2.0.10.
1 General provisions
2 General requirements of design
3 Calculation of grid structures
3.1 General calculation principles
3.2 Calculation principles for space truss displacement method
3.3 Simplified calculation method
3.4 Principle of calculation of internal forces under actions of earthquake and temperature
3.5 Principles for calculation of composite grid structures
4 Design and construction of members and joints
4.1 Members
4.2 Welded steel plate joints
4.3 Welded hollow spherical joints
4.4 Bolted spherical joints
4.5 Bearing joints
4.6 Joint structure of composite grid structures
5 Fabrication and installation
5.1 General requirements
5.2 Requirements for fabrication and assembly
5.3 High-altitude bulk method
5.4 Stripping or partitioning installation method
5.5 Aerial sliding method
5.6 Whole hanging method
5.7 Integrated lifting method
5.8 Integral jacking method
5.9 Construction of composite grid structures
5.10 Acceptance
Annex I Common grid forms
Annex II Internal force calculation equation and equivalent stiffness of grid member by simulating sandwich plate method
Annex III Table of bending moment and deflection of peripherally simply supported grid with rectangular plane form by simulating sandwich plate method
Annex IV Simplified calculation of vertical seismic action effect of grid structure
Annex V Simplified calculation of composite grid structure
Annex VI Drawing for joint structure of commonly used welded steel plate
Annex VII Drawing for joint structure of composite grid structure
Annex VIII Material performance and calculation structural requirements of rubber pad
Annex VIIII Explanation of wording in this specification
