They are showing on tv a special on how the new World Trade Center, building 1, is being built. Focusing on the steel and the guys fitting everything together.Where do builders go to buy all that steel framing? We do not build really tall buildings where I live so most of the steel is cut and welded on the job site. At World Trade Center 1, they seem to get the steel on trucks; already cut and welded.
Most of the parts are cut, welded, and fabricated indoors in a welding shop at another location. Then they're trucked to the site and simply need to be bolted together. This is made possible through the use of computer aided design and modeling programs, so that parts can be made to fit almost presciently in the field. They buy the steel from steel companies. I couldn't tell you exactly where it comes from, you'd have to ask the contractors themselves.
The steel is all custom fabricated in what are called structural steel fabrication shops. Each Building is designed by architects then the frame is designed by engineers to support whatever load is being applied to the building. After the engineering is done it goes out for a bid package where a fab shop estimates how much to charge for the fabrication of the steel and the erection of the steel. Once a company wins the bid, it then has to design how the steel will connect with one another and have it approved by an engineering firm to assure the connections are strong enough. Once all of that happens the fab shop orders raw steel beams and angle iron and steel plate at stock lengths. Beams are then cut into the right length and holes drilled in the proper places. The beam is then marked with a number that tells the erectors where it goes. The steel is then shipped out in batches to the construction site where it is unloaded and shook out into an organized place to grab them with a crane. They are then put together like a toy model, there are instructions that say what beam goes where and what size bolt to use. The welding you see being done is on really critical moments that need extra strength. That is about how it goes in a nutshell. It is a bit more complicated than that but it gives you an idea.
