How is the steel structure grid constructed?

The construction methods of steel structure grid can be divided into three types, which are described below:

Frist, high altitude assembly method

The steel grid is installed by the high-altitude assembly method, which is to first set up the assembly bracket at the design position, and then use a crane to hoist the grid members (or blocks) to the design position in the air, and assemble them on the bracket.

This method sometimes does not require large lifting equipment, but the amount of assembled brackets is large, and there are many high-altitude operations. Therefore, it is more suitable for high-strength bolted steel structure grids made of section steel or steel pipe grids with bolted ball joints. At present, there are still some steel grids constructed by this method.

Second, the overall installation method

The overall installation method is to first assemble the net frame on the ground into a whole, and then use lifting equipment to lift the whole to the design position to fix it. This construction method does not require tall assembling brackets, requires less work at high altitudes, and is easy to ensure welding quality, but requires heavy lifting equipment, and the technology is more complicated.

Therefore, this method is more suitable for steel structure grids with spherical joints, especially steel grids with many members such as three-way grids. According to the different equipment used, the overall installation method is divided into multi-machine lifting method, pulling rod lifting method, jack lifting method and jack lifting method.

Third, high altitude slip method

In recent years, the use of high-altitude parallel slip method for construction of grid roofs has gradually increased, and it is especially suitable for theaters, auditoriums and other projects. In this construction method, the steel structure grid is usually assembled with an assembly platform on the roof of the front hall of the building, and an assembly platform can also be set up on the auditorium stand for assembly. After the first assembly unit (or the first section) is assembled, drop it onto the sliding track, and use the traction equipment to slide it forward for a certain distance.

Next, assemble the second unit (or the second segment) on the assembling platform, and slide forward together with the first assembling unit (or the first segment). In this way, the assembly will continue to slide forward until the entire steel structure grid is assembled and slid to the position.

After the sliding of the assembled steel mesh frame, a roller can be set under the support of the mesh frame, so that the roller can slide on the sliding track. The support bottom plate can also be set under the steel structure grid support, so that the support bottom plate slides along the embedded steel plate embedded on the reinforced concrete frame beam.

The sliding of the grid frame can be pulled by a winch or a lever hoist. According to the size of the traction force and the bearing capacity of the rods between the grid supports, one or more points of traction can be used. When the steel grid slides, the asynchronous value at both ends should not be greater than 50mm.

When the sliding method is used to construct the steel structure grid, in the process of sliding and assembling, the steel grid should be checked as follows:

①When there is no fulcrum in the middle of the span, the internal force of the member and the mid-span deflection value.

②When there is a support in the middle of the span, the internal force of the member, the reaction force of the fulcrum and the deflection value.

When the internal force of the rod is changed due to the addition of intermediate slide rails in the sliding unit of the steel grid frame, temporary reinforcement measures should be taken to prevent instability. The high-altitude sliding method is used to construct the steel grid structure, because the grid assembly is carried out on the roof platform of the front hall, which reduces the risk of high-altitude operations. Compared with the high-altitude assembly method, the assembly platform is small, which can save materials and ensure the assembly quality of the grid.

Due to the sliding construction used for the assembly of the steel structure grid, it can be parallel to the civil construction and cross three-dimensionally, so the construction period of the entire project can be shortened. The high-altitude sliding method has simple construction equipment and generally does not require large-scale lifting and installation equipment, so the construction cost can also be reduced.