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Construction Technology of Bolted Ball Space Frame Structure ( Part 2 )

3.5.1、Crane station location and arm length

Use 3 cranes for hoisting work. First check the running status of the crane, prepare enough fuel, and determine the station of the crane according to the distance between the lifting point and the crane station. Second, check the extended height of the crane boom. When lifting the bar space frame horizontally, if the extension height of the crane arm does not meet the requirements, the hook will form a dead angle, so it has to fall back to the space frame and re-lift. The bar space frame that has been hoisted for the second time is easily deformed, which may eventually affect the quality of the whole project.

3.5.2、Selection and fixation of lifting points

During the hoisting process, the location of the hoisting point should be selected strictly in accordance with the hoisting requirements. Accurately check the stability of the lifting point to ensure smooth and safe lifting. The hanging point rope adopts 20mm steel wire rope, which are respectively fixed on the upper string node of the space frame, and the hanging point is wrapped with cotton cloth to prevent it from slipping. In addition, pay attention to that the turnbuckle at the end of the rod must not be strangled by the wire rope, so as not to affect the quality of hoisting construction.

3.5.3、space frame slitting

Hoisting method: Install the three supports between the two spans on the top of the column, and use a level to check the height. If there is any error, it should be corrected and leveled temporarily. After slitting, the weight of the space frame is about 36 tons. The hoisting weight of two 100T cranes is 32 tons, and the hoisting weight of one 35T crane is 4 tons. Each crane has 4 lifting points, and each crane adds a hand chain hoist between the wire ropes as needed to adjust the level of the space frame after lifting, so as to facilitate the butt joint assembly of the space frame. When the space frame is lifted to more than 1 meter above the support, the large space frame stops lifting, and the 35T crane controls the small space frame to rise and fall slowly so that the two space frames are parallel, and at the same time adjust the small space frame and the large space frame with a chain hoist The slope is consistent. After slowly approaching, connect the longitudinal upper and lower chord members, and install the web member after the connection is tightened. After the installation is completed, the space frame slowly descends, put the end ball joints into the support support, and weld the ball joints to the support, and the support and the embedded steel plate firmly. The order of installing the second space frame is the same as before, but before the space frame is slowly seated and falls into the support, the upper and lower chords of the space frame must be tightened with the bolt balls of the space frame installed for the first time, and then the end ball joints must be tightened. Put it into the support bracket, and tighten the web frame interwebs installed twice at the same time.

3.5.4、Hoisting operation coordination and safety precautions

All on-site personnel participating in the hoisting operation must hold a certificate to go to work, and they must obey the command and act in a unified manner during on-site operations to ensure their own safety. Before hoisting, organize the mechanical department to comprehensively check whether the hoisting machinery such as cranes and ropes are in good condition, check whether their models, specifications and safety performance meet the construction requirements; check whether the hanging parts are firmly tied, and whether the center of gravity and lifting points are accurate. All the machinery on site must work within the rated load, and avoid overloading. During the hoisting process, it is forbidden to pull or hang obliquely; it is forbidden to lift hanging objects of unknown weight and half-buried or linked hanging objects. When hoisting, lift the hanging parts in a balanced manner, and do not make the hanging parts swing or vibrate randomly. When the hanging part is 0.1m away from the fulcrum, stop the machine and check whether the rope binding the hanging part is strong and whether the crane is stable, and continue lifting after ensuring everything is normal.

When lifting and lowering the hanging objects, no one is allowed to go up and down with the hanging objects without permission, so as to avoid unexpected situations that may cause casualties. Set eye-catching warning signs on the hoisting site, and non-operating personnel are not allowed to enter. When hoisting, no one can stand under the hanging object, so as to avoid casualties caused by the sudden fall of the heavy object. Outdoor operations are prohibited in rainy, foggy or windy weather conditions. If it is necessary to hoist at night in order to catch up with the work, instructions from relevant departments should be obtained, and good lighting conditions must be ensured on site. During the lifting process, if the operation is to be interrupted, necessary measures should be taken to ensure the safety of the personnel on site. The lower chords of the space frame are all closed with safety nets, the personnel passages are built with 5cm wooden boards, and a safety rope slideway is set near the passageway, and the slideways use steel wire ropes.

4、bolt ball space frame technical quality measures

4.1、 Mandatory inspection

All space frame balls, rods, high-strength bolts, sleeves, and support plates entering the site must have the manufacturer’s material delivery certificate, mechanical performance, and chemical composition analysis report. The sealing plate of the cone head of the rod is a secondary weld flaw detection ratio of 20%. Every specification of high-strength bolts must undergo a hardness test, and all clubs must undergo a pull-out test. The deflection of the space frame structure must be inspected after the roofing project of the space frame structure is completed. For the space frame structure with large and medium spans, the center point of the lower chord and the quarter point of the lower chord span must be measured.

4.2、space frame error adjustment and bar inspection and secondary fastening

After installing a set of bar space frames, it is necessary to adjust the error according to the vertical and horizontal axes. After installing all the space frames, check and accept the space frame rods as required, and replace the deformed rods in time. Before the roofing project is performed, tighten all the sleeve screws of the rods again. There should be no gaps in the pressure rods to ensure that the high-strength bolts are tightened. After the installation is completed, the gap of the tie rod sleeve and the redundant bolt holes should be filled with oil putty, and anti-corrosion treatment should be carried out according to the regulations.

4.3、Eliminate the stress of space frame installation

When the space frame is installed and connected together, the space frame rods will show different stress states. After a complete set of space frame structure is constructed, it is almost inevitable that the space frame will be deformed due to the non-concentration of stress caused by installation, but measures must be taken to release this stress until it is eliminated. Specific measures: When installing the space frame, do not weld the support and the support surface all at once. When the first sub-strip space frame is installed and aligned, after eliminating the error, weld the rest except the support at the docking position. The support and supporting surface make the whole space frame stable. After the second slitting space frame is installed, find the alignment, and after eliminating the error, weld the support and the support surface of the first slitting space frame firmly. When the entire roofing project is completed, the load loading is basically completed, the entire space frame is in a state of uniform stress, and the horizontal displacement of the space frame is basically completed.