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2023-04-06The bolt-ball joint space frame has become a widely used load-bearing structure. From the perspective of structural mechanics, this system belongs to multiple statically indefinite space structure systems. The space frame structure integrated the engineering plane shape and span size, roof structure, architectural design, and other requirements. This kind of space frame structure has high spatial stiffness, strong integrity, good seismic performance, rhythm, novel and beautiful, and is more and more widely used in large-span roof-bearing structures. There is a food court in the Liuxiang Mall project that uses a bolt ball node space frame with an all-glass lighting roof, which has a good effect.
1 Space Frame Skylights Project Overview
Liuxiang Mall Food Square is located on the top floor of the commercial-03-floor building. The structure of the building is a frame structure, and the column mesh size is 9m×9m. The glass lighting roof is laid on the space frame, and the axis dimension of the whole space frame is 54m wide and 27m. The space frame structure is adopted with the regular quadrangle bolt ball node. The support mode of the space frame is the lower string support—professional factory processing, site scattered, and block lifting. The space frame structure is a point-supported all-glass daylighting roof, and the sandwich tempered glass is connected with the space frame structure through stainless steel claws. The whole roof view transparent, spacious space, style, and generous, fully reflects the beauty of the system.
2 Lighting Roof Space Frame Structure
2.1 Plane layout space frame 54m in length and 27m in width, using regular four corner bolt ball nodes, the mesh size of the upper and lower strings are 1.5m×1.5m, and the height of the network frame is 1.5m. space frame roof drainage using space frame arch.
2.2 Support
The lower string multi-point support, the supporting point is the frame side column and the middle column, the bearing is A3 steel plate, the side column bearing is plate rubber bearing, the middle column bearing column cap is plate rubber bearing.
2.3 space frame rod
The space frame rod is an ordinary A3 seamless steel pipe with an outer diameter of 50mm and a wall thickness of 3mm, which meets the slenderness ratio standard stipulated in the code.
2.4 Spherical node
The node is a bolt ball node, which is composed of bolts, steel balls, screws, sleeves, cone heads, sealing plates and high-strength bolts. The steel balls are made of 45 steel, bolts, screws, sleeves, cone heads, sealing plates, and high-strength bolts are made of A3 steel. The horizontal rod is welded at both ends of the conical head, and the inclined rod is connected to the steel ball by high-strength bolts.
2.5 Arch Lifting
In order to meet the requirements of roof drainage and structural deflection, the arching ridge line is along the long side of the space frame. Arch 50mm at the center line of the short side, and the roof slope reaches 3‰. The Arch ridge line is along the long side direction of the space frame. Arch 50mm at the center line of the short side, and the roof slope reaches 3‰.
3 Glass Roof Skylight Systems
The skylight roof is all made of glass, and the glass is made of laminated tempered glass. It is customized in professional factories according to the design and lofting drawing, and shipped to the site for installation after unified numbering. The roof adopts a point support type, the glass is connected to the mesh frame through stainless steel claws, and the glass joints are filled with sealant. The drainage slope of the roof is realized through the arch of the space frame.
3.1 Fabricating of space frame
All bolt balls, rods, and supports of the space frame are made in professional factories. They are processed according to the national standard GBJ205 steel structure engineering construction and acceptance specifications, JGJ7-91 space frame structure design and construction regulations, and JGJ78-91 space frame structure engineering quality inspection and evaluation standards. The precision of rods and nodes is guaranteed by processing on special molds. The screw thread of the bolt ball is processed in accordance with class 6H precision, and the weld seam of the rod is controlled in accordance with Class II quality inspection standards. After processing, try assembling on special assembling die to ensure the precision of the small assembling unit. After processing, the rod, bolt, and wire mouth are treated with rust prevention and corrosion prevention. After the completion of the production, the experience will be collected and shipped to the site.
3.2 Glass roof production
The glass is made in a professional factory according to the design and lofting drawing and is accepted after the air tightness, water tightness, and wind pressure resistance test. After acceptance, the glass is uniformly numbered and packed to the site.
4 Assembly of space frame
4.1 Assembly process
Small single cone – assembly lifting block – Erection of an entire shelf – block lifting – inspection.
4.2 Check before assembly
Before disassembling, check the material quality certification documents and make quality certification documents, according to GBJ205 steel structure engineering construction and acceptance specifications, JGJ7-91 space frame structure design and construction regulations, and JGJ78-91 space frame structure and quality inspection and evaluation standards for inspection, and check the rust prevention and anticorrosive effect of various components, and qualified to start small single cone.
4.3 Small single cone
A single cone is formed by small assembling on the special assembling mold frame. The deviation of the control chord length and the height of the cone is not more than ±2mm, and the deviation of the diagonal length of the upper chord is not more than ±3mm. After assembling the single cone, check the anti-rust and anti-corrosion quality of the rod. For high-strength bolts and dowel positions, after tightening the bolts, oil putty will be used to insert all joints tightly, and the excess bolt holes of the bolt ball will be closed for anti-rust and anti-corrosion treatment.
4.4 Assembling hoisting blocks
Assemble the single cone into a 3m×3m hoisting unit block according to the lofting drawing. Control the length deviation of the block unit is not more than ±5mm, the center displacement deviation of the node is not more than 2mm, the height deviation of the cone is not more than ±2mm, the diagonal length deviation of the upper string is not more than ±3mm, the center displacement deviation of the lower string node is not more than 2mm, and the single cone will not be deformed. After assembling, channel steel shall be used for reinforcement to prevent deformation in the hoisting process, and the number shall be uniformly according to the lofting drawing.
4.5 Erection of scaffolding
The bowl buckle scaffold is used to set up full steel tubular scaffold, laying 10×10 wooden keels and laying bamboo plywood on top, as a platform for hoisting, calibration and inspection. The shelves will not be removed until the glass top of the whole roof is completed.
4.6 Installing Supports
According to the lofting diagram, set the axis of the support, and according to the roof slope requirements precisely set the elevation of the top of the support, according to the axis and elevation pull the line in the top of the frame column installation space frame support, control the displacement deviation of the support is not greater than 2mm, elevation deviation is not greater than ±2mm. Support installation is completed for acceptance, acceptance began to block lifting.
4.7 Hoisting in Blocks
Tower crane hoisting, strictly control the deformation of the hoisting unit, check the deformation of the whole space frame and the quality of slope and arch, check the solid quality of the bolts of each node of the space frame, check the quality of rust prevention and corrosion prevention of each component, and finally fill each screw hole and bolt joint with oil putty tightly, brush two times on the loss of anti-rust paint. Finally, all the space frame members were sprayed with two fireproof coatings, and the quality reached the provisions of CECS in “Technical Specification for Application of Fireproof Coatings on Steel Structure”.
The bolt-ball joint space frame has become a widely used load-bearing structure. From the perspective of structural mechanics, this system belongs to multiple statically indefinite space structure systems. The dome skylight space frame structure integrated the engineering plane shape and span size, roof structure, architectural design, and other requirements. This kind of space frame structure has high spatial stiffness, strong integrity, good seismic performance, rhythm, novel and beautiful, and is more and more widely used in large-span roof-bearing structures. There is a food court in the Liuxiang Mall project that uses a bolt ball node space frame with an all-glass lighting roof, which has a good effect. technical Specification for Application of Fireproof Coatings on Steel Structure”.
