The Structural Steel Supply Chain
The four distinct components of the structural steel industry supply chain are:
||Producers of structural steel products including hot-rolled structural shapes (wide flange beams, plate, channels and angles) and manufacturers of hollow structural sections (formerly known as tubular steel).|
||Service Centers that function as warehouses and provide limited preprocessing of structural material prior to fabrication. |
|Structural Steel Fabricators
||Structural Steel Fabricators that physically prepare the structural steel for a building through a process of developing detailed drawings (the work of a detailer) based upon the construction drawings provided by a structural engineer; material management; cutting; drilling; shop fitting (bolting and welding); painting (when required); and shipping.|
||Erectors that construct the structural steel frame on the project site by bolting and field welding structural steel components together according to the construction documents.|
Three major mill producers account for over 90% of all wide flange structural steel produced in the United States. Five producers, including the three major mills, supply the market with miscellaneous hot-rolled shapes such as angles and channels. All hot-rolled products are produced utilizing electric arc furnaces utilizing ferrous scrap as the primary feed stock. The use of scrap results in an average recycled content of 88% for all hot-rolled structural material produced in the United States.
Production of hot-rolled structural steel in the United States typically exceeds 8 million tons. Approximately 6 million tons represented wide flange sections. It is estimated that 65% of domestic consumption of structural steel is utilized in building projects under roof, 16% in non-building structures and 19% for non-structural applications.
Hollow Structural Sections (HSS) for building applications are produced by a significant number of manufacturers. The domestic market for hollow structural sections in 2007 was approximately 3 million tons.
Steel plate used in building projects is produced by a variety of mills specializing in plate production.
Service Centers stocking all types of structural material are located throughout the United States. 70% of material flows through service centers to fabricators, with the remainder of the material being supplied directly from producing mills to fabricators. A listing of AISC member service centers is available here.
Topping Out : A Wide Range of Wide-Flange, MSC, October 2008
Service Center Brochure
It is estimated that there are more than 2,600 steel fabricators in the United States supplying fabricated structural steel to building projects. The American Institute of Steel Construction represents 750 of these fabricators that produce structural steel. The typical structural steel fabricator is a family owned business employing from 10 to 100 employees. Employee classifications include detailers, shop workers, equipment operators, welders, painters, delivery drivers and administrative personnel. Projects may range from the fabrication of several tons of structural steel for a small retail store to tens of thousands of tons for large, high rise structures. A very rough rule of thumb would indicate one ton of steel would be required for every 200 square feet of building area.
The fabrication process is driven by plans developed and sealed by licensed structural engineers specifying all design aspects of the structural components of a building based on the building layout developed by an architect. Upon award of the project the fabricator is typically responsible for creating detail drawings of each piece of structural steel. These details are produced by a steel detailer and refine the design drawings from the structural engineer developing a dimensionally accurate drawing of the member including all connection details. Steel detailers may either work directly on the staff of the fabricator or on a sub-contract basis. The detail drawings are then submitted to the structural engineer for approval.
Following a determined sequence optimized for erection in the field, the appropriate structural steel members are then cut to the proper length, drilled or punched and all additional shop work is performed on the member. When required, the member is cleaned and coated with paint or galvanized. The members are then grouped in the order in which they will be erected in the field, placed on truck for shipping and delivered to the project site.
A typical fabrication project will require between 10 and 20 hours of shop time per ton of fabricated steel. Material costs account for between 30% and 35% of the final cost of the fabricated and erected structural steel. Fabrication and erection costs for structural steel vary greatly based on the type of structure being constructed, the number of pieces, local labor conditions and the complexity of the connections. An AISC member fabricator in the area of the project (a list of member fabricators is available on the AISC web site) or the AISC Steel Solutions Center (866.ASK.AISC) is the best source for fabrication costs for a specific project. The practice of minimizing the weight of the structural steel in a building is often short-sighted as lighter sections, while satisfying the strength requirements of the structure, may result in more costly connections and fabrication procedures.
A Complete Fabrication, MSC, March 2008
Erectors are the most visible component of the structural steel supply chain, performing the actual construction work at the project site. Most erection is performed under the same contract as the steel fabrication, with the fabricator either providing in-house erection services or sub-contracting the erection work to a qualified firm. Field erection involves assembling the structural components in proper sequence while maintaining the structural stability of the partially completed structure. Stringent safety standards have significantly reduced the number of injuries occurring during steel erection. The erection team is also responsible for bringing the final structure into “plumb” within the required tolerances.