The overall installation method is to first assemble the structure on the ground into a whole, and then use lifting equipment to raise the whole to the design position to be fixed. This construction method does not require tall assembly brackets, has less high-altitude operations, and is easy to guarantee the welding quality, but it requires heavy lifting equipment and complex skills. Therefore, this method is more suitable for the steel structure of the ball joint (mainly the structure with more members such as the three-way structure). According to the different equipment used, the overall installation method is divided into the multi-machine lifting method, the pulling rod lifting method, the jack lifting method and the jack lifting method.

      1. Multi-machine lifting method

      This method is used for small and medium-sized structures with small distance and weight. Before hoisting and installation in Guizhou, perform dislocation assembly operations on the structure on the ground (that is, the assembly position is staggered by some distance from the installation axis to avoid the position of the column). Then, multiple cranes (mostly crawler cranes or truck cranes) are used to raise the assembled structure above the top of the column as a whole, and then fall into place after being shifted in the air.

     (1) Structure assembly

      After the steel structure is processed in the metal structure factory, the single-piece flat truss or three-dimensional truss assembled into small units is transported to the construction site, and the site assembly is to assemble the small unit truss into the entire structure at the assembly position. The key to structural assembly is to control the size of the structural frame axis support (the amount of welding shrinkage to be pre-released) and the arching requirements.

Structural welding is mainly the welding of sphere and steel pipe. Generally, equal-strength butt welding is used. For safety, a fillet weld of 6-8mm is added to the butt weld. For weldments with pipe wall thickness greater than 4mm, the joint should be grooved. In order to make the butt weld uniform and the length of the steel pipe slightly adjustable, a sleeve can be added. When assembling, install the upper and lower chords first, and then install the oblique webs. After all the steel pipes between the two trusses are put in and corrected, the steel pipes are welded one by one.

     2. Structure hoisting

      This kind of medium and small structures are usually lifted by four crawler hoists (or truck-type and tire-type cranes), and they can also be lifted by two crawler cranes or a lever.

      When the structure is lifted to a height of about 30cm higher than the top of the column, perform an air displacement to move the structure above the top of the column. When the structure is in position, Guizhou Hoisting In order to make the center line of the structure accurately coincide with the center line of the column top, a steel wire rope is tied to each of the four corners of the structure in advance, and the inverted chain is used to align the line.

      (1) Pull rod raising method

      For the installation of the large steel pipe structure of the ball joint, the pulling rod raising method is currently used in my country. When constructing with this method, the structure is first assembled in a staggered position on the ground, and then the whole structure is raised above the top of the column with multiple single-leg pull rods, shifted in the air, and installed in position.

     (2) Principle of air displacement

      Air displacement is the key to this method. Aerial displacement is to use the unequal horizontal force in the lifting pulleys on both sides of each pull rod to move the structure horizontally.

      When the structure is displaced in the air, two or more pull rods are required to hang the structure, and the lifting pulley group on the same side does not move. Therefore, when the structure is displaced in the air, it only translates and does not tilt. Since the pulley group on the same side does not move, in addition to translation, the structure can also control circular motion, and the structure will drop slightly. The direction in which the structure shifts in the air is related to the arrangement of the pull rod.

    (3) Selection and arrangement of lifting equipment

      The selection and arrangement of lifting equipment is an important issue in the construction of structural shift rod raising. The content includes: pulling rod selection and hanging point arrangement, cable wind rope and ground anchor arrangement, hoisting pulley block and lifting point rigging method, hoist arrangement, etc.

      The arrangement of the cable wind rope should make multiple pull rods connected to each other as a whole to increase the overall stability. Each pulling rod must have at least 6 cable wind ropes. The cable wind rope should be calculated and selected according to the load of wind load, hoisting weight, pulling rod deflection, and initial stress of the cable wind rope. Ground anchors also need to be calculated.

      The force calculation of the lifting pulley block can be carried out according to the actual force, and the specifications of the pulley are selected according to the calculation results.

      The specifications of the hoisting machine in Guizhou shall be determined according to the internal force of the hoisting wire rope. In order to reduce the difference in catch lift, try to use winches of the same specification.　　

    (4) Axis control

      The position of the structural assembly pillar should be accurately measured according to the axis of the installed pillar to eliminate the accumulation of axis error when the pillar is installed.

     (5) Pull rod removal

      After the structure is hoisted, the pull rod is enclosed in the structure and should be dismantled by upside down. This method is to hang two sets of lifting pulleys at the upper chord node of the structure to hang the pull rod, and then remove the pull rod one by one starting from the next section.

      3. High-altitude sliding method

      In recent years, the use of high-altitude parallel sliding method for construction of structural roofs has gradually increased, and it is mainly suitable for theaters, auditoriums and other projects.

      The sliding of the assembled structure can be equipped with rollers under the structural support to make the rollers slide on the sliding track; it can also be equipped with a support base plate under the structural support so that the support base plate is pre-embedded on the reinforced concrete frame beam The embedded steel plate slides.

      The structure slippage can be hauled by a winch or a lever hoist. According to the traction force and the bearing capacity of the rods between the structural supports, one or more points can be used for traction.

      When slipping, the out-of-sync value at both ends should not be greater than 50mm. When using the slip method to construct a structure, during the slipping and assembling process, the following checking calculations should be performed on the structure:

      (1) When there is no fulcrum in the middle of the span, the internal force of the rod and the deflection value in the middle of the span;

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

      When the internal force of the structural sliding unit changes due to the addition of the intermediate slide rail, temporary fixing measures should be taken to avoid instability.

      The high-altitude sliding method is used to construct the structure structure. Since the structural assembly is carried out on the roof platform of the front hall, the risk of high-altitude operations is reduced; compared with the high-altitude assembly method, the assembly platform is small, which can save materials and ensure the assembly quality of the structure; Because the sliding construction for structural assembly can be parallel to the civil construction, the construction period of the whole project can be shortened; the high-altitude sliding construction equipment is simple, and generally does not require large-scale lifting and installation equipment, so the construction cost can also be reduced.