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Grid design principles

更新时间:2021-02-05 09:40:40?点击:499 ? Grid Knowledge

The grid structure is a high-order statically indeterminate space frame structure. It is very difficult to analyze its internal force and deformation very accurately. Therefore, the calculation of the grid structure must be the same as other structures to ensure the safety of the structure. Under the premise, proper simplification of node stiffness, support conditions, member deformation, etc. are carried out to adapt the calculation method to engineering needs.

The design and calculation of the grid structure should follow the current relevant national or industry standards. These standards include: "Grid Structure Design and Construction Code", "Building Structure Load Code", "Steel Structure Design Code", "Cold Formed Thin-Wall Steel Structure Technical Code", "Building Seismic Design Code", etc.

At present, the calculation model of the grid structure can be divided into three types, namely, the calculation model of the space articulated rod system, the calculation model of the cross beam system and the calculation model of the plate system. The spatial hinged beam system calculation model simplifies the grid into a hinged rod assembly with two-force rods as the calculation unit; the cross beam calculation model simulates the grid as a cross beam system and uses beam segments as the calculation unit , First obtain the internal force of the beam and the node displacement, and then back to obtain the internal force of the member. According to whether the influence of shear deformation is considered, there are various calculation methods; the calculation model of the plate system is to simulate the grid frame as orthotropic or For an isotropic flat plate, the internal force of the plate is calculated first, and then the internal force of the rod member is calculated back. If this calculation model does not consider the influence of shear deformation, it is called the pseudo-plate method; if the influence of shear deformation is considered, then It is called the pseudo-sandwich method.

The general calculation principle of the grid structure is:
(1) The internal force and deformation of the grid structure should be calculated under the external load, and the internal force and deformation under the action of earthquake, temperature change, support settlement and construction and installation load should be calculated according to the specific situation. The above calculations can be carried out in an elastic phase.
(2) The influence of node stiffness can be ignored in structural analysis. The nodes are assumed to be spatially hinged nodes, and all members only bear axial force.
(3) The external load is based on the principle of static equivalent, and the load in the area under the jurisdiction of the node is concentrated on the node. However, when there is a local load acting on the member, the influence of the local bending moment should be additionally considered.
(4) The support conditions can be assumed to be hinged supports or elastic supports that can be moved sideways in one direction or two directions, or without side movement, according to the rigidity of the support structure and the structure of the support nodes.

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