What is a steel frame?

A steel frame consists of a skeleton frame structure comprising of horizontal I-beams and vertical steel columns fitted in a rectangular grid building construction to brace the floors, walls, and the roof of the building held onto the frame. Due to the implementation of this methodology, the construction of the skyscrapers was feasible.

History

The production and distribution of steel for structural use were slow in the past. In the 1880s, construction dependent on mild steel started and the quality and quantity of steel made increased gradually. In 1885, the Home Insurance Building was the foremost to bring the skeleton framework into demand and ditching the load-bearing technique. In 1890, Rand McNally Building in the U.S. was the first of its kind for using steel-framed buildings.

Steel framing system

Square and round tubular sections of steel, filled with concrete are used. The steel beams are attached to the columns with bolts and threaded fasteners, and into olden times, were connected by rivets. The center of the steel called the web is usually wider than the column web for prevention of the higher bending moments in beams.

Broadsheets made of steel deck are used as a top-covering of the steel frame under the dense layer the top of the steel frame and below, a thick layer of concrete and reinforced steel bars. Generally, in office buildings, the final floor surface is given by a kind of raised flooring system with the space between the walking plane and the structural floor being used for cables and ducts.

The steel frames are required to be away from fire as the steel softens at large temperatures which may lead to collapsing of the building structure partly. In the case of the columns, this is usually done by enclosing them in a certain form of fire-resistant structure such as masonry, concrete, or plasterboard. In the 1970s, the asbestos material was extensively used for fireproofing of steel framing but was discarded since it causes certain health issues.

The architectural drafts are scanned to make sure that all types are marked appropriately, fire-rated assemblies are seen and the relevant details are given for MEP (mechanical, electrical, and plumbing works) details and conveyed to the structural engineers. The outer part of the building is anchored to the steel framing system by the usage of various building and construction methods or just painted for protection of the steel from the climatic conditions.

Cold-formed steel frames

Cold-formed steel frames, also known as lightweight steel framing (LSF). These are thin galvanized steel sheets that may be transformed into steel studs for utilization as structural or non-structural building materials for exterior as well as partition walls in commercial, industrial, and residential construction. The vertically placed steel studs are equally spaced 16 inches apart fixed at both ends. Also, steel framing is simpler to deal with since the steel studs weigh 1/3^rd less than the wood studs.

Usually, the C-shaped stud and the U-shaped track are considered for residential construction projects. The thickness of the manufactured framing members is 12 gauge to 25 gauge. The outside perpendicular wall studs are capable of resisting heavy wind loads like hurricanes near coastal areas. Light gauge steel (25 gauge) is used where there are no axial and very weightless lateral loads like in the interior construction where the members are framing of walls between rooms. The wall finish is always anchored to the two flanged on either side of the stud.

The Steel mills generate galvanized sheet steel which is the base material for the production of cold-formed steel profiles. The steel sheets are further hot-rolled which are then used for framing. The steel framing gives high ductility in design as the strength-to-weight ratio of steel is more.

Steel-framed walls are considered to have inbuilt and splendid acoustic and thermal characteristics which are the major properties when building using cold-formed steel. Studs spacing is 16 inches at the center for houses and 24 inches at the center for office buildings.

Wood framing system

Researches have conveyed that a stick-framed steel system may cost 15% more than wood framing. Steel framing can cost similar to or less than wood framing. Steel framing is usually spaced at 24 inches and wood framing is normally spaced at 16 inches. Due to Covid-19, the work must be completed as soon as possible for maintaining social distancing and reduction to the virus exposure. Thus, cold-formed steel accelerates the development of the building by 50% than wood framing.

Structural steel framing

Structural steel framing is a building frame where the formation of vertical and horizontal structural elements is made by a system of structural steel beams and columns. Various forms or categories of structural steel framing for buildings are inclusive of the skeleton, wall bearing, and long-span steel framing systems.

Skeleton steel framing

A skeleton frame is frequently utilized for multi-story structures and involves a network of joining beams and columns which hold the floors and outer walls and sustain the loads till the foundation of the building. For attachments between column and beams, components used are metal-framing brackets, gusset plates, and so on for spreading the stresses.

Wall bearing steel framing

It refers to the construction of masonry walls on the inside as well as the perimeter of the building. The structural steel members are then anchored on the walls using steel plates and bolts.

Long span steel framing

It is used for broad spans with a huge clearance requirement, where standard beams and columns are not correct. A span that exceeds the length of 12 m is called a long span and assists to give alterable space for the floor and installation of a variety of services. It can be subdivided into trusses, girders, arches, and rigid frames.

Ordering steel framing materials

It’s vital to know about the various shapes, acronym ‘STUFL’ where ‘S’ is a stud, ‘T’ is a track, ‘U’ is U channel, ‘F ‘is furring and ‘L’ is L-header.

Context and Applications

This topic is taught in courses related to:

• Bachelors of Technology in Civil Engineering
• Masters of Technology in Civil Engineering
• Masters in Technology (Structural Engineering)
• Masters in Technology (Infrastructure Engineering)

Practice Problems

1. Which of the following is used for interior construction with no axial and light lateral loads?

1. Light gauge steel
2. Non-load material
3. Non-structural material
4. Shear walls

Correct option- a

Explanation: Light gauge steel is used for interior construction with no axial and light lateral loads.

2. Which of the following statements is incorrect?

1. In architectural drafts, the fire-rated assemblies must be mentioned.
2. The sheets must be hot-rolled before being set for framing.
3. By ditching the load-bearing technique, Rand McNally Building was the first one to adopt steel framing in the world.
4. The components of skeletal steel framing include metal-framing brackets.

Correct option- c

Explanation: By ditching the load-bearing technique, Home Insurance Building was the first one to adopt steel framing in the world.

3. The more the strength-to-weight ratio, the higher is the-

1. Size of shear walls
2. Value of non-load material
3. SFIA
4. Steel framing ductility

Correct option- d

Explanation: The more the strength-to-weight ratio, the higher is the steel framing ductility.

4. What is the thickness of the framing members created?

1. 10 gauge to 23 gauge
2. 12 gauge to 25 gauge
3. 14 gauge to 27 gauge
4. 16 gauge to 29 gauge

Correct option- b

Explanation: The thickness of the framing members created is 12 gauge to 25 gauge.

5. What is the required length of a long span?

1. 10 m
2. 11 m
3. 12 m
4. 12.5 m

Correct option- c

Explanation: The required length of a long span is 12 m.

Related Concepts

• AISI standards (American Iron and Steel Institute’s prescriptive method)
• Design standards online buying at Steel Framing Alliance’s website
• Framing during Covid-19 pandemic