1.What connection methods are suitable for on-site assembly?
High strength bolt connection
Principle: The shear force is transmitted by applying high preload to generate strong friction between the connected steel plates, and the bolts themselves mainly bear tensile force.
Advantages: Fast construction speed, easy quality inspection and control, removable, relatively small damage to the galvanized layer (mainly in the bolt hole area), it is the most important on-site connection method for prefabricated steel structures.
2.What are the precautions for high-strength bolt connections?
Treatment of the connection surface (friction surface) is key. A zinc coating (especially hot-dip galvanizing) significantly reduces the coefficient of friction. The design must use a proven coefficient of friction for galvanized surfaces (usually much lower than bare steel treated with sandblasting), or use a specially treated friction surface (such as aluminum spraying, inorganic zinc-rich paint, etc., but this increases costs and needs to be coordinated with the galvanizing process). You can also choose to use bolted connections with a higher "slip coefficient" designed specifically for galvanized surfaces (such as washers with specific coatings or treatments).
3.What are the advantages and disadvantages of ordinary bolt connections?
Advantages: Low cost and relatively simple installation.
Disadvantages: Lower load-bearing capacity than high-strength bolts, larger deformation, and relatively poor seismic performance. Mainly used for secondary connections, temporary support or occasions with less force.
4.What are the advantages and disadvantages of self-drilling and self-tapping screws?
Advantages: Extremely fast and convenient installation, no need for pre-drilling and tapping, especially suitable for connecting thin steel plates (such as purlins, wall beams, roof panels, wall panels and other enclosure systems to the main structure).
Disadvantages: Limited bearing capacity, mainly suitable for the connection of light steel keel structures or non-load-bearing enclosure structures. There is local damage to the galvanized layer (drilling and thread formation).
5.What are the advantages and disadvantages of soldered connections?
Advantages: High connection rigidity, direct force transmission, good sealing, and can form connection nodes of various complex shapes.
Disadvantages:
The most serious damage to the galvanized layer: The high temperature of welding will burn the large area of galvanized layer in the weld and its heat affected zone (HAZ), forming a serious corrosion weak point.
Zinc vapor hazard: The zinc vapor generated when welding galvanized steel is extremely harmful to the health of welders (causing "metal fume heat"), and forced ventilation and personal protection are required.
Risk of welding defects: The zinc layer may cause defects such as pores, lack of fusion, and cracks during the welding process.
Professional welders and strict quality control are required.
Usually prefabrication is required in the factory, and on-site welding is less efficient and conditions are limited.