Overall lifting construction of large-span steel structure space frame in aircraft maintenance hangar (Part 1)

With the reform and opening up and economic development, steel structure engineering is gradually developing from industrial buildings with high requirements such as large spans, high-rises, and heat resistance to civil buildings. With the wide application and technological update of steel structure space frame and truss structures, in recent years, more and more large-span space frame structures are constructed using the overall lifting method. The biggest advantage of this method is that it can save a lot of temporary support and The construction period is relatively short, and the difficulty lies in the control of the lifting point, the large ventilation pipes in the space frame and the fire pipe space frame. During the construction process of the G2 and G3 aircraft maintenance depot projects of Baiyun Airport, the construction process was optimized for steel space frame assembly, lifting, pipe space frame installation, and independent column construction, which improved construction efficiency and safety.

1 Engineering example

The G2 aircraft maintenance depot project of an international airport has a construction area of 10,325m2. The roof is a steel structure space frame roof, and the supporting system is a reinforced concrete column + inter-column support. The north-south span of the space frame is 137m, and the east-west depth is 68m. , The clearance height in the hangar is 24m.

The hangar hall of the G3 aircraft maintenance warehouse of an international airport has a span of 76m + 76m and a depth of 68m. The steel structure of the roof adopts a two-layer orthogonal and inclined square pyramid space frame height 5m. The painting hall adopts the ventilation form of comprehensive air coverage from the top to the bottom. The air supply outlets are arranged in the space frame of the hangar hall. The diameter of the air duct is 500-2100mm. The construction of the roof steel structure of the G2 and G3 aircraft maintenance depots adopts the method of ground assembly and overall lifting. The overall lifting is completed by a computer-controlled hydraulic lifter. The lifting point is selected on the reinforced concrete column as a permanent support, and a total of 13 lifting point are set.

2 In-situ assembly technology of roof steel space frame

2.1 Quality control of pre-arching

When the space frame is in normal use, the rods will deflect downward due to their own weight and load. In order to avoid excessive deflection and affect the safety and use of the structure, the space frame is pre-arched during assembly. Use SFCAD2000 and SAP2000 software to calculate the deflection of the space frame, and take it as the reverse pre-arch value of the space frame. When the space frame is assembled, it is positioned according to the structural design size and the pre-arch value.

2.2 Assembly and positioning quality control

A tire frame is set under each node ball of the lower chord. The main material of the tire frame is a steel pipe with a height of 50cm, and a short round tube is set on the upper part to adjust the elevation. The projection point of the center of the lower string ball of the space frame on the ground is the positioning point of the tire frame, and the center of the node ball is checked with a total station.

2.3 Assembly sequence control

Choose a reasonable assembly and welding sequence before assembling the space frame structure to reduce space frame deformation caused by welding shrinkage deformation, avoid excessive deformation of the overall structure, and affect structural stability and safety.

2.4 Welding quality control

Take a reasonable overall welding sequence: symmetrical from the middle to both sides; local welding sequence: first lower the chord ball joints, then top the chord ball joints, so as to reduce the space frame deformation caused by welding shrinkage deformation, avoid excessive deformation of the overall structure, and affect the stability of the structure sex and safety. Witness sampling and retesting of raw materials and welding materials in accordance with relevant national specifications, formulate welding procedure evaluation before welding, and compile welding procedure instructions; clean up, preheat, interlayer temperature control, heat preservation, etc. before welding according to the requirements of corresponding specifications The operation of the process, and send a special person to monitor and record the process; do a good job of welding protection measures to ensure a good welding environment and avoid the impact of the external environment on the welding quality.

3 Construction technology for overall upgrading of large-span roof space frame

The plane size of the steel grid frame of this project is 137m×68m, and the net height is 24.5m. According to the structural characteristics and existing construction technical conditions, it should be installed in the way of “ground assembly, overall lifting, and partial post-installation”. How to reasonably arrange the lifting points and select Proper lifting and lowering points are the difficulties of this project, and the synchronization and monitoring in the overall lifting process are the key points of this project. Considering the stress and deformation of the structure, the construction period, and the construction cost, etc., the construction technology of “ground assembly and overall upgrading” was selected to complete the grid roof construction of this project. According to the structural characteristics of the steel grid, the arrangement of the lifting points should follow the principle of symmetry, combined with the performance of the hydraulic lifter and the results of the construction simulation simulation analysis, in accordance with the principle of minimizing the replacement of the original design rods. In order to ensure that the steel roof is in a stable state during the lifting process, the lifting synchronization control is very important. The hardware adopts hydraulic lifter and hydraulic pump station, and the software adopts synchronous control system. Before the official lifting, lift the grid frame to 300-500mm from the ground and hover for 24 hours. After checking that the grid components, lifters, and hoisting steel strands are normal, the grid frame will be lifted formally.

4 Large-span roof space frame overall lifting/tensioning simulation simulation analysis technology

Since the number of supports and boundary conditions are different from the original design state during the lifting process, the stress state of the entire structure will also change. Therefore, it is necessary to carry out an integrated computer simulation analysis of the space frame lifting, unloading and prestressed tensioning to ensure that the entire construction safe and feasible. Use computer software to simulate and analyze the stress of different lifting conditions of the space frame, determine the optimal lifting point setting plan, and determine the material section selection of the lifting frame through the simulated collision analysis between the lifting steel truss and the permanent space frame structure components, and then Simulate and analyze the force situation of the space frame during the lifting process, so that the structural force during the overall lifting meets the boundary conditions of the structural design. The lifting point is selected on the permanent structural column by simulating and analyzing the stress situation. Through computer simulation calculation and analysis of the stress situation of reinforced concrete structural columns used as lifting pillars, and through the installation of temporary inter-column supports and permanent inter-column supports to connect the independent columns into a whole, increase the stability of the columns at the lifting point, and then ensure the lifting space frame stability and security.