Steel Structure Connection and Construction Technology of High Strength Bolt

The components of the steel structure are composed of section steel, steel plates, etc. through connection, and each component is then installed with a connecting frame to form the entire structure. When designing the connection, the principles of safety and reliability, clear force transmission, simple structure, convenient manufacture and saving steel must be followed. Steel structure connection construction is an important part of steel structure design. The connection methods of steel structure can be divided into welding connection, rivet connection, bolt connection and fastener connection for light steel structure. At present, welded connections are the most widely used, followed by bolts. Rivet connections are basically not used in building structures due to the labor and material costs. High-strength bolts are one of the most widely used methods along with welding, and they develop rapidly, with obvious advantages and broad prospects.

一. Selection of welding methods for steel structures

In the field of installation of steel structures, arc welding is widely used. In arc welding, coating electrode, manual electrode, automatic submerged arc welding, semi-automatic and automatic CO2 gas shielded welding are the main products. In some special occasions, electroslag welding must be used.

1. Manual welding: manual welding equipment is simple and easy to operate, and can be used for welding in any space, but it is labor-intensive and inefficient. It is divided into AC welding machine and DC welding machine. AC welding machine uses welding rods and welding parts The arc heat welding generated between them is suitable for welding ordinary steel structures. The DC welding machine is suitable for steel structures with high welding requirements, with high cost and stable arc. The disadvantage of manual welding is that it has a great relationship with the technical level and mental state of the welder, it is easily affected, and the quality department is stable.
2. Submerged arc automatic welding: Submerged arc automatic welding has become arc welding, which is a welding method in which the arc burns under the flux layer. It has high efficiency, good quality, low operating technical requirements, and good working conditions. It is used in the production of large components. The widest range of efficient welding methods. It is suitable for butt and fillet welds with large welding lengths, generally regular straight welds.
3. Semi-automatic welding: It is basically the same as submerged arc automatic welding, and the operation is flexible, but it is not convenient to use. Suitable for welding short or curved butt and fillet welds.
4. CO2 gas shielded welding: solid wire or flux cored welding with CO2 or inert gas shielding, simple equipment, easy operation, high welding efficiency and good quality. It is suitable for automatic welding of long welds of components.
5. Electroslag welding: use the resistance heat welding generated by the current passing through the liquid slag, and can weld large thickness welds. It is suitable for full-penetration connection between box beam and column diaphragm and panel.

二. Key points of welding process

Welding connection is the most important connection method of modern steel structure. The structure of welding connection is simple, and any form of components can be directly connected; the material is economical, and the section is not weakened; the production and processing are convenient, and automatic operation can be realized; Great stiffness. Pay attention to the following points when welding:

1. Welding process design: determine the welding method, welding parameters, specifications and models of welding rods, welding wires and fluxes, etc.
2. Electrode baking: Electrodes and powder-cored wires must be baked according to the quality requirements before use. After the low-hydrogen electrodes are baked, they should be placed in the incubator for use.
3. Positioning spot welding: When the welding structure is splicedand assembled, the exact position of the parts must be determined, and positioning spot welding must be carried out first.
4. Preheating before welding: Preheating can reduce the cooling rate of the heat-affected zone and prevent welding delay cracks.
5. Determining the welding sequence: generally start from the center of the weldment and expand to the surroundings; first weld the weld with a large shrinkage, and then weld the weld with a small shrinkage; try to weld symmetrically; when the welds intersect, the longitudinal weld first , after cooling to normal temperature, weld the transverse weld again; when the steel plate is thicker, weld in layers.
6. Post-weld heat treatment: Post-weld heat treatment is mainly to dehydrogenate the weld to prevent cold cracks. Post-weld heat treatment should be carried out immediately after welding, and both preheating and post-heating can be carried out with a diffuse flame gun.