Precise Positioning Technology of Space Frame Support in Large Maintenance Hangar (Part 1)

The overall lifting technology is one of the commonly used methods for steel space frame structure construction. The space frame is first assembled on the ground or concrete structure, and then the overall lifting equipment is used to lift it into place, and finally the space frame and the support foundation are connected. In this process, the support is in place as the last link, and its deviation will be adversely affected by various factors such as component processing accuracy, space frame assembly accuracy, space frame fixation, existing deviation of the support foundation, etc., and it is easy to cause excessive deviation. LF combined with the installation process of the heavy-duty space frame in the 747 paint maintenance hangar of the Capital Airport, expounded several measures to ensure the positioning accuracy of the support.

The 747 painting maintenance hangar project of the Capital Airport is currently the largest special painting hangar in China. The total construction area is 21150㎡. The roof of the painting hall is a double-layer welded ball flat space frame, and the space frame at the door warehouse is a three-layer. It is an oblique quadrangular pyramid double-layer welded ball space frame with size of 5m×5m, the thickness with 5m～6.275m, and the lower chord elevation is 26m. The span of the space frame is 85m, the length is 105m, the maximum specification of the steel pipe is Φ325x30mm, and the maximum specification of the welding ball is WSR800x32 (with double ribs). The space frame has a total weight of about 1,000 tons and is supported around. The support ball and the column top plate are connected by four high-strength bolts, and after unloading , the support bottom plate is welded and fixed with the column top plate. The space frame installation adopts the overall lifting technology of cable net and axial pressure rod, that is, the space frame is assembled on the ground, and is lifted by the overall lifting system of cable net and axial pressure rod, then the seat is closed.

Construction photos of the overall lifting of the space frame

Photo of the connection between space frame support and top of the column

The Main Factors Affecting the Position Deviation of Bearings and Countermeasures

Before the construction, according to the problems of large support deviation and heavy repair work that occurred in similar projects in the past, a detailed research and analysis was carried out from the aspects of construction process and construction measures in each process, and the problems that caused the support to be in place were found out. The main reason for the large deviation has formulated countermeasures, which mainly include the following measures.

Reasonable selection of the overall construction sequence

In many existing space frame constructions, the space frame is often raised above the design elevation first, and then the rest of the rods on the edge of the space frame are assembled (all the support balls are assembled with the space frame as a whole) before being placed. With this process, the bolt holes on the bottom plates of all the supports of the space frame must be aligned with the bolt holes on the top plate of the steel column at the same time, which greatly increases the difficulty of controlling the deviation in position. Therefore, in this project, the method of closing and assembling directly at the design elevation is adopted. Each support is respectively butted with the top of the steel column. The length of the rods is adjusted according to the actual size between the support and the space frame. In this way, the difficulty of simultaneously docking all the supports of the space frame is resolved, and it is easier to ensure the positioning accuracy of each support.

Ensure the assembly accuracy of the space frame

The assembly accuracy of the overall size of the space frame is an important prerequisite to ensure the accuracy of closing. On the one hand, it is necessary to strengthen the size control of the space frame assembled on the ground. To ensure the assembly accuracy of the space frame, first of all, there must be a reliable assembly foundation. In this project, the space frame is assembled on the ground, and the ground is compacted before construction, and a 1m×1m concrete pad with a thickness of 100mm is made under each bottom string ball block, and then the steel pipe supports the lower string ball to ensure the stability of the support. During the assembly process, strictly prevent rods and balls from being used incorrectly, and strengthen the measurement and inspection of cell size, and correct any problems found immediately. On the other hand, it is necessary to ensure the assembly accuracy of the high-altitude closing part. There are often suspensions in the closing part, and workers need to work at heights. A reasonable and reliable operating environment must be created to facilitate the operation of workers in order to ensure assembly accuracy and construction safety. In this project, according to the structural characteristics, scaffolding boards are covered on the top of the lattice column, and guardrails, safety ropes, etc. are set up. The measures are safe and reliable, and create a good operating environment for controlling assembly deviation.