Construction of long-span special-shaped gymnasium (Part 1)

1 Project overview

The canopy for the grandstand of the large stadium is crescent-shaped on the plane, 183.5m long, 39.6m wide at the widest point, with a maximum cantilever of 30.0m, fan-shaped laterally, and a sagittal height of 24m. The plan view, front view and side view are shown in Figure 1~3. The structure adopts the space structure  grid with bolted ball nodes, the grid size is 3.7m x 3.7m, the height of the grid is 2.88m, and the angle of the rods is about 45°. The supporting structure under the space frame is a reinforced concrete structural column. The elevation of the top of the column is 12m. Due to the irregularity of the entire structure, the high-altitude bulk method is used for installation.

2 Characteristics and difficulty of project construction

The structure is composed of vertical trusses and transverse trusses with inverted quadrangular pyramid spherical node grids to form a space truss structure. It is crescent-shaped in plan view, arched in front view, and has a large inclination angle on the side. The lowest point elevation is 8m+11.1m=19.1m, and the highest point elevation is 8m+27.6m=35.6m. The space frame is narrow and long in the whole plane. According to the past installation experience, the whole structure must eliminate the cumulative error, and the installation accuracy must be confirmed from time to time. In order to control the error in the installation process, the best installation method is to use sub-area installation, and finally connect each area to form a stable whole. However, the overhang of the space structure  is also very large, the maximum overhang reaches 30m, and the overall stability of the space structure  is not formed after the division of areas, and the stiffness and internal force of the members are unpredictable. It is possible that during the installation process, the excessive stress of individual rods may cause excessive deformation and even cause the overall loss of stability of the regional network frame, resulting in safety accidents. According to the research of the project team, first install the support area of the network frame according to experience to form a small whole to increase the overall rigidity, and then divide the plane of the cantilever area installed later into three installation areas, and the middle area, with one crescent at the head and tail on each side area. The center is continuously pushed toward the two ends, and the two ends are moved closer to the center. When the area is installed, the lower support is added as needed, and the deflection of the space frame is monitored from time to time. When the deflection is too large, it is necessary to add support and fix it at the point where the deflection is too large.

3 Processing of components

3.1 Fabrication of rods

There are two types of rods, which are usually divided into two forms according to the size of the pipe diameter. The larger diameter of the rod is made of a cone head, and the smaller diameter of the rod is composed of a sealing plate (cone head or strength bolts inside the sealing plate). Steel pipe rods are blanked according to the design length. After cutting, the length deviation control value of the rods is +1mm, and the verticality of the end surface is a<1mm. The matching steel pipes, cone heads or sealing plates and high-strength bolts are taken according to the regulations of the sample drawing. Use the pinch welding sealing plate on the mold or the cone head and the steel pipe to be welded with full penetration, the gap control value at the root of the weld, the precision is: b=2 + 1mm, s<10mm; b=3 + 1mm, 10mm<s< 15mm (b weld gap, s-steel pipe wall thickness); the weld reaches the second grade, and ultrasonic flaw detection is required. The installation process of rods is generally: steel pipe blanking-chamfering-joint assembly-welding-rust removal-painting-numbering packing-inspection-storage.

3.2 Bolt ball processing and production

The bolt ball is generally a solid ball. Check whether there is overburning or cracks on the bolt ball: use a magnifying glass and magnetic particle inspection, the ball blank diameter deviation control accuracy is: D<120, +2.0~-1.0; D>120, +3.0~- 1.5. The threaded hole and surface processing should be carried out according to the following process: splitting the surface, drilling the threaded bottom hole, chamfering the hole, and tapping the thread. The threaded hole is processed on the lathe with special tooling, the threaded hole and the plane are clamped and processed at one time, and the ball number and the processing job number are printed on the process hole plane. The processing flow of the bolt ball is generally: rough ball→drilling reference hole→reference hole tapping→secondary clamping→processing screw hole (each step is the same: milling→drilling→tapping)→screw hole inspection→numbering→ Rust and paint. Each component in the production project must have a processing record, which must be filled in by the quality inspector. Send it to the construction site together with the finished product for inspection by the supervisory owner and relevant departments.