There are many forms and types of steel structures, and there are also different classification methods. It can be classified according to the force characteristics of the long span steel structures, or according to the force transmission path. Long span steel structures can be divided into plane structures and space structures. The planar structure can be subdivided into various prestressed structures formed by analysis frames, arches, steel cables and steel tie rods. Spatial structure can also be subdivided into thin shell structure, grid structure, reticulated shell structure and various prestressed structures. The basic components or basic units that make up the structure, namely the plate shell unit, the beam unit, the rod unit, the cable unit and the membrane unit, classify the space structure.
The classification according to the stress characteristics of long span structures is simple and clear, which can reflect the stress characteristics of the structure and is familiar to designers. Therefore, this standard classifies long span steel structures according to the mechanical characteristics of the structure.
The design principles of long span steel structures are stipulated.
1. Designers should choose the appropriate long span structural system according to the specific conditions of the project. The support form of the structure should match the mechanical characteristics of the structure. The support should provide vertical constraints and necessary horizontal constraints for structures that are mainly subjected to overall bending, and provide reliable horizontal constraints for structures that are mainly subjected to overall compression. Provide reliable anchorage for tension-based structures, and set up reliable out-of-plane support systems for planar structures.
2. When analyzing grid frames and double-layer reticulated shells, it can be assumed that the nodes are joints, and the rods only bear axial force, and the rod element model is used. When analyzing the single-layer reticulated shell, the joints should be assumed to be rigidly connected, and the rods can bear not only the axial force, but also the bending moment and shear force, and the beam element model is adopted. When analyzing the frame, it should be determined according to the structural form of the joint and the internode length of the bar or the ratio of the length of the bar to the height (or diameter) of the section, and determined in accordance with the relevant regulations in the current standard technical specifications for concrete filled steel tube structures. When the steel cables and steel tie rods in the model are simulated as flexible components, the calculation models of various rods should be able to reflect the stress state of the structure.
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