Brief introduction of deepening design of space frame processing

 The space frame structure is a form of building structure composed of supports, pipes, ball joints and enclosure systems. It belongs to the fastest growing and most widely used space grid structure.

Different from the primary and secondary relationship between the components in the plane structure system, the space frame structure is composed of a whole continuous space body or expanded by many steel bars. Each of its components is a part of the overall structure. The geometrical characteristics of the structure share the load, the internal force transmission is simple, and the structural integrity is good. Therefore, a large span can be realized with a smaller section, reduce the structure's own weigh, and improve the overall economic effect.

Interpretation of the 4 parts of the deepening design of the space frame structure

　　1. Deepening design of bearing nodes

　　 Support node deepening modeling 

The space frame is generally placed on the top of the column, the top of the beam and other lower supporting structures, and the support node refers to the grid node on the supporting structure. The deepening design of space frame first starts with the support nodes. The elevation and position of the support nodes determine whether the construction of the space frame can be carried out normally.

The following points need to be paid attention to in the deepening of bearing nodes:

　　 The elevation of the top surface of the lower concrete structure or steel structure and the position of the embedded parts are required to be accurate.

　　 The node form of the support needs to be determined. Rubber flat supports and basin supports are widely used. the restraint direction of the supports should be pay more attention to .

　　 Side bearing nodes are often close to the parapet wall. Pay attention to the clear distance between the bearing node and the parapet wall, and generally keep it above 50mm.

The middle support has a large bearing capacity, and the size of the bottom plate is often large. It is necessary to pay attention to whether the section of the lower concrete column or steel column meets the requirements. If the requirements are not met, the enlarged column head joint should be used.

For the upper chord support type grid, the support position rods are often easy to collide with the lower support structure, and need to pay attention to review. The distance from the bottom of the support ball joint to the support bottom plate should meet the requirement that the inclined web rod does not collide with the column or connecting beam.

　　 The outer side of the space frame support needs to take limit measures.

2. Deepen the design of the ball joint

　　 Grid ball joints are divided into two types: welded ball and bolted ball. The bolted ball is connected by high-strength bolts, and the welded ball is connected by on-site welding.

　　 The following points should be paid attention to in the deepening design of the ball joint:

　　 There are differences among the manufacturers of bolt ball joint fittings, and the fitting data should be obtained before deepening.

　　 The materials of the steel balls, high-strength bolts, sleeves, fastening screws, cones or sealing plates in the bolt ball joints shall meet the requirements of the design and specifications.

The grades of the high-strength bolts in the bolt ball joints should be selected according to the specifications.

　　 The diameter of the bolt ball shall ensure that adjacent bolts do not collide in the sphere and shall meet the requirements of the sleeve contact surface.

　　 The tapered heads or sealing plates at the ends of the rods in the bolt ball joints are connected by welding, and the bearing capacity of the connecting welds should not be lower than the connecting steel pipes; the cone section and the thickness of the sealing plate should be calculated and determined according to the actual force.

The welding ball is generally a hollow ball welded by two hemispheres, and it is necessary to determine whether to install stiffeners according to the magnitude of the force.

The ratio of the outer diameter of the welded ball to the wall thickness, the ratio of the outer diameter of the ball to the outer diameter of the main steel pipe, and the ratio of the ball wall thickness to the wall thickness of the main steel pipe need to meet the specifications: the ratio of the outer diameter of the ball to the wall thickness should be 25~45 , The ratio of the outer diameter of the ball to the outer diameter of the main steel pipe should be 2.4~3.0, the ratio of the wall thickness of the ball to the main steel pipe wall thickness should be 1.5~2.0, and the wall thickness of the ball should not be less than 4mm.

Groove welds should be used to connect the welded ball to the steel pipe, and a gap should be left between the steel pipe and the ball to ensure that the weld penetration reaches the same strength as the steel pipe.

When the number of connecting rods of the welded ball joint is too large, in order to reduce the the ball diameter, part of the rods are allowed to meet, but it should meet the structural requirements specified in the specification: the axis of all the intersecting rods must pass through the center line of the ball; The large rod must be welded to the ball in full section (when the cross-sectional area of the two rods are equal, the tension rod is taken), and the groove of the other rod is welded to the intersecting rod, but it should be ensured that 3/4 of the cross section is welded to the ball. And should set up stiffening ribs as required; for rods with large forces, support plates can be set up as required.

 

3. Deepening design of support nodes

　　 Support node deepening modeling

　　Support node is the tie that connects the space frame structure and the enclosure structure, and is often arranged on the upper chord and side of the grid.

The deepening design of support nodes need to pay attention to the following points:

On the premise of meeting the force requirements, high-strength bolts should be used for the connection between the support and the ball to reduce the amount of high-altitude welding on site.

The top plate of the support should be set in a circular shape to ensure that the support can be positioned and installed when rotating 360 degrees along the shaft center of the steel bar.

When the height of the support is large, diagonal bracing should be installed to ensure the lateral stability of the support.

4. Deepening design of purlin gutter enclosure system

　Deepening modeling of roof purlin gutter enclosure system

　Purlin enclosure system of space frame often adopts the form of primary and secondary purlin connection, the main purlin often uses I-beam, rectangular tube section, and the secondary purlin often uses C-shaped section.

The main purlin and support, main purlin and sub-purlin connection should adopt bolt connection.

When a rectangular pipe section is used, attention should be paid to the end of the purlin to be blocked to avoid corrosion due to the inconvenient anti-corrosion treatment inside.

After the above points of work

The deepening design phase of the space frame is now complete.

The space frame structure has various forms, which can present various shapes of building planes, and the architectural shape is light and beautiful, and the space is solid. At the same time, it can meet the large span requirements with low steel consumption. Therefore, it is widely used in stations, airports, and exhibitions. Large buildings such as pavilions. The deepening design of the space structure is different from other steel structure types. It needs to be completed by combining different software such as Tekla, 3D3S, MST, etc. It requires designers to be more comprehensive and able to use different tools and software to seamlessly connect the deepening design in various details.