Steel Fabrication is the process used to manufacture steel components that when assembled and joined, form a complete frame. The frame generally uses readily available standard sections that are purchased from the steel stockholder , together with other specialist items.
Although a wide range of section shapes and sizes are produced, the designer may find that the required section size is not available. In this case, you need to discuss your requirements with an expert on steel fabrication.
As machinery takes over from the tape measure the frame is produced to high quality standards which are reflected in the speed and accuracy of steel erection on site . This results in significant benefits both to the client and the contractor.
Note: it is important that frames in steel structures must have the required degree of lateral resistance to wind loads.
Modern steel fabrication equipment can cope with complex individualistic designs but, in general, the more complex the fabrication the greater the cost. Steel fabrication is more economic with:
- Single square end cuts
- One hole diameter on any one piece avoids drill bit changes
- Holes in flanges and webs aligned where possible
- Web holes having adequate flange clearance
- Rationalised range of fittings for connections
- The use of a small range of standard bolts
Wherever possible, leave the choice of the connection detail to the steelwork contractor as the type and design of connections directly influences the total frame cost. Complex designs are going to cost, even with modern equipment. If you wish to keep costs down – keep it simple!
Ensure that the most appropriate sections are specified for the particular application. “I” sections are usually most economical in conventional framing, while tubular sections are an alternative for columns and long span trusses. Asymmetric beams are often used to reduce the construction depth of floor systems. Plate is used for steel fabrication connections, stiffeners and base plates.
Ensure that unnecessary finishing is not specified and that any applied corrosion resistant coating is appropriate for the environmental conditions to be encountered. Grinding of welds to improve the appearance of the steel is usually only required for exposed steel in close proximity to a building’s occupants.
Quality of Engineering and Documentation
Completeness and accuracy of information are vital for steel fabrication to be accurately assessed for the work involved. Where steelwork is pre-designed, ensure that all member sizes are shown and that the connection forces are shown or are available. Guidance on identifying the requirements for the production and exchange of accurate, timely and detailed information for projects involving steelwork is available .
Steel Fabrication Processes
Advances in quality in steel construction are largely due to developments in steel fabrication machinery. The manufacturers of steel fabrication equipment have invested heavily in research and development to produce the technological advances required by today’s construction sector.
Essentially, the welding process uses an electric arc to generate heat to melt the parent material in the joint. A separate filler material supplied as a consumable electrode also melts and combines with the parent material to form a molten weld pool. The weld pool is susceptible to atmospheric contamination and therefore needs protecting during the critical liquid to solid freezing phase. Protection is achieved either by using an inert shielding gas, by covering the pool with an inert slag or a combination of both actions. As welding progresses along the joint, the weld pool solidifies fusing the parent and weld metal together. Several passes or runs may be required to fill the joint or to build up the weld to the design size
It is important that the steel fabrication specification (and accompanying drawings) for a project should express clearly the particular requirements for the steel structures . Failure in clarity will lead to extra provisions for risk and extra costs in resolving queries. The project specification should also avoid over-specification – requiring unnecessary quality and excessively tight tolerances will lead to higher costs. The project specification should generally follow recognized industry standards.