Key points of steel structure design
First of all, we should pay attention to the synergistic work of the upper and substructure, and take into account the effect of multi-direction seismic action. The most reasonable method to consider the coordination of upper and lower structures is to calculate the seismic action according to the whole structure model. Substructure simplification must be based on reliability and dynamic principle, that is the effectiveness of equivalent stiffness and mass should be considered comprehensively.
The design model is modeled by software, and the calculation and analysis are carried out. During the specific operation, the calculation model should be reasonably determined to ensure that the connection between the roof and the main supporting parts is consistent with the structure. In addition, stress analysis should be considered. In addition to simulating the stress of the whole structure after forming, the special stress of the construction process should be taken into account in the calculation and analysis, so as to avoid the damage caused by the local stress exceeding the design value before forming the structure. The calculation and simulation of the construction process need to consider components hoisting, working conditions in different construction stages, structural pre-deformation technology, components pre-assembly, unloading, etc.
The structure arrangement
The structure layout should avoid the formation of weak parts due to local weakening or mutation, resulting in excessive internal force and deformation concentration. For the possible weak parts, measures should be taken to improve the seismic capacity. Therefore, the balance of mass and stiffness distribution, the integrity of the structure and the clear transmission of force should be ensured when the structure is arranged.
The seismic action of the roof should be effectively transmitted down through the supports. To avoid the roof internal force concentration or large torsion effect, the roof, support and substructure layout should be uniform and symmetrical; To ensure the integrity of the roof structure, the spatial force transmission system should be adopted first and the weak parts of local weakening or mutation should be avoided. The light roof system should be used, so the unit weight of the roof system should be strictly controlled.
Key points of quality control of steel structure
Mounting accuracy control
The measurement and control of the complex space steel structure should be carried out during the installation. Because the measurement and control of steel structure construction is a part of the construction technology, the rationality and advancement of its engineering construction scheme can be analyzed from a large number of measurement and control data and obtained the reaction and confirmation. For the large-span steel structure, because the deformation and stress state of the structure are very different from that after forming in the construction process, it is necessary to use a variety of support tire frames to ensure the accuracy of the structure.
Because the large-span steel structure has the characteristics of large unloading tonnage, wide distribution of unloading points, large unloading force at a single point, and large workload of unloading calculation and analysis, the structure will be damaged or the scaffold will gradually become unstable if the supporting force is not released reasonably. Therefore, the unloading of steel structure must take the system conversion scheme as the principle, the structural calculation and analysis as the basis, the structural safety as the purpose, the deformation coordination as the core, the real-time monitoring as the guarantee, and the operation in strict accordance with the requirements of two unloading methods of equal ratio method and equal distance method.
Large span steel girder hoisting, if not reasonable lifting point calculation, still choose traditional two segments, due to the steel structure is longer, lifting point spacing is bigger, and the factors such as weight and variable load, the axial force of the steel beam and wire rope are very big, prone to beam lateral bending, or even more serious deformation. The construction site of the long-span steel structure should strengthen the management and increase the workers' professional knowledge training so that they can have a more concrete understanding of the mechanical characteristics of components and hoisting knowledge. At the same time, strengthen the construction organization design to carry on the reasonable demonstration of the hoisting scheme, in order to choose a more reasonable hoisting scheme.
The installation sequence
Since the installation sequence of a long-span steel structure is high, the safety of the structure may be affected if the installation sequence is not considered reasonable and the steel components do not meet the needs of hoisting. During the construction organization and design, the installation sequence shall be reasonably arranged. Factory processing, component transportation and on-site installation shall be coordinated in a unified way. During the construction process, the installation shall be strictly implemented. In addition to carefully working out the installation sequence suitable for the project, experienced construction teams should also be selected for installation to avoid potential quality hazards.