High-altitude in-situ element is one of the common construction methods for large-span steel structures

 Steel structure installation is a highly technical engineering task, of which the high-altitude in-situ installation method is one of the common installation methods, this method mainly includes two technologies: high-altitude in-situ bulk method and high-altitude in-situ unit installation method.

The high-altitude in-situ bulk method, as the name suggests, is a method of assembling components directly at the final location of a building. This type of installation usually involves fixing the steel member in the designed position by means of overhangs or full supports. The implementation of this method requires first to build a solid full support structure, which is not only to ensure that the steel members can be stably shelved in the high air, but also to provide a reliable operating platform for the construction personnel. The advantage of this method is that because the weight of a single steel member is relatively light, it can significantly reduce the lifting capacity requirements for lifting equipment. However, it also has some shortcomings, such as the construction of the support structure takes a long time, the amount of high-altitude work, the construction period may be extended accordingly, and the need to use a large number of support materials, which will occupy a larger space inside the building. This method is usually suitable for those large-span structural projects such as grids or reticulated shells that are not particularly large in span and have relatively loose construction requirements.

Compared to the bulk method, the high-altitude in-situ unit installation method is a more refined and efficient installation technique. The core of this method is to reasonably divide the whole structure into several unit modules, and then hoist these modules one by one to their final position in the design and install them. In order to ensure smooth installation on site, it is recommended that these units be pre-assembled in the factory. The key to this method is to reasonably plan the division of lifting units, and the following are some important considerations:

The size of the unit should be determined according to the lifting capacity of the crane selected and the specific form of the structure. For example, for long-span steel truss structures, the location of the block should not be set in the mid-span part of the truss to avoid unnecessary structural stress.

For the beam-column structure, it is generally recommended to place the section position at the reverse bending point in the design, which can better adapt to the mechanical characteristics of the structure.

For the grid and reticulated shell structure, block or strip schemes can be used according to the specific situation to facilitate installation and adjustment.

Each unit must be an independent system with sufficient stability, stiffness and strength to ensure safety and structural integrity during hoisting and installation.

Through such careful planning and execution, the high-altitude in-situ unit installation method can effectively improve the efficiency and safety of steel structure installation, and is an indispensable technical means in modern steel structure construction.