System Components

        Beams, Columns, Girders, Plates, Trusses, Foundations

 

A structural system executed using steel framing contains a number of different components that interact to provide stability to a building. The most basic combination of steel members is the post and lintel configuration - columns supporting beams or girders. These basic members can then be configured into trusses, or other forms necessary for bracing structures.

 

The most basic use of steel framing is in buildings with mostly rectangular floor plans which are bounded in their corners by steel columns with steel beams and girders spanning the distance between to form the floor for the next level, or the roof for the current one. Floor trusses span the gaps between the beams and girders, and floor systems form the final surface in contact with everything that will ever pass over the floor. Depending on the envelope type, steel studs form the walls with gaps bounded by steel headers and sills for windows and doors.

The various structural members in a building are tied together using many varieties of plates, connections, hold-downs, straps, and tie-downs, among others. All of this steel framing is placed on top of foundations that can be composed of slabs of reinforced concrete, piles driven into the ground, concrete footings, aggregates, or anything else that could plausibly keep a building from sinking into the ground or falling over.

 

Applied Loads

The whole purpose of the structural system in a building is to transfer various loads from their points of origin into the ground. There is a great variety of loads that needs to be accounted for when designing the structure for a building. The most common load types are dead load and live load. The dead load is the load of the structural members themselves and any permanent fixtures in the building such as walls, shear walls, and HVAC equipment. The live load is the load from objects that move through the structure, like people, and non-permanent furniture. There are also loads that originate from outside of the structure, and are more dependent on factors such as a building’s location, size, and shape. These loads are induced by wind, rain, and snow, along with heat and cold, and seismic activity. Depending on the location’s building codes, there may even be a necessity to design for blast or impact loads, or tsunami loads. Everything must be considered, otherwise the structure could become unsafe for habitation.

 

Compared to some of the more exotic structural systems being employed in the world today, steel framing is fairly basic in the way that it transfers loads through the structure. Live loads are usually caught on the floor system which transfers the loads to underlying floor trusses which transfers them to beams and then finally to the columns and the foundations. Similar principles can be applied to the vertical dead and dynamic loads exerted on buildings, however to cope with horizontal wind loads, it is sometimes necessary to place structural members such as shear walls, or even large reinforced concrete cores to carry the loads to the foundation and prevent the building from swaying too much.