What is concrete framing?

A concrete frame is a structure formed by the interconnection of beams and columns to form a structural network. In simple terms, it is the basic skeletal structure of a building or any construction. The concrete framing structure is built on a concrete foundation that forms the base of the entire structure. The concrete frame system is built to support floors, roofs, walls, beams, rafters, joists, etc.

The primary components of a concrete framing structure are the beams, columns, and slabs. Beams are the horizontal structural elements which carries the transverse shear loads of the building, while slabs are the flat structures where people generally stand and walk. Columns are the vertical members carrying axial compressive loads and support the beams and slabs. Damaging a beam effects the respective floor of the building, but if a column is damaged, it destroys the entire building.

Precast concrete vs prestressed concrete

Precast concrete frame systems are mostly used for low-rise structures and single storey buildings. The precast concrete frames forms the basics of construction before the actual construction is initiated. These precast concrete frames are brought to the construction site by trucks and erected by cranes and lifts. There are different types of precast concrete frames like skeletal frame, H-frame, and portal frame.

Skeletal frame

This type of frame is mostly used in UK. When the frame is under vertical loadings, more sagging moments are generated in the beams while a little moment is generated in the column. But the column moments increases significantly under the external lateral loads.

H-frame

The bending moment of the H-frame is similar to the in-situ frame. This frame can support lateral loads and transfers the wind loads to the frame and joints. The major difficulties of using H-frames are that they are bigger and weigh significantly in tons, and are rather difficult to transport.

Portal frame

These frames are mostly used for industrial warehouse applications. The bending moments associated with these frames are similar to H-frame and in-situ frame.

Prestressed concrete is an engineered concrete. These category of concrete are prestressed, i.e. they are compressed during their production. This method allows the concrete to provide excellent tensile strength during their service of operation. The concrete is constructed using high strength tensioned tendons which are embedded inside the concrete. These tendons may be single wired or multiwired and are made from high strength steel, carbon fiber, and aramid fiber. Constructions related to complexes, bridges, buildings, residential areas, etc are some of the application of such types of concrete.

Reinforcement in concrete

The concrete reinforcement is the fundamental way of strengthening a concrete framing system. Concrete is a brittle material, hence it provides excellent strength regarding compressive loads. But brittle materials are weak in tensile strength and has poor ability to resist tensile loads. Concrete reinforcement is done to overcome this drawback. Reinforcement is typically done using steel bars. A structural foundation is created using the steel bars, or depending on application, a structural network is formed. These structural forms the skeleton of the reinforcement. Masonry mixture, or concrete mixture is poured over this structural formulation of bars. Upon setting of the concrete it forms a single structure. The bars are intentionally made using ductile materials as ductile materials have superior tensile strength. These combination of concrete and bar network is majorly known as reinforced concrete. Reinforced concrete can thus resist both compressive and tensile loads.

Beams, columns, and slabs are made using reinforced concrete as these are the major load bearing structures of the concrete framing system. Slabs are one of the important structural elements of the concrete frame systems, it is always a flat horizontal structure that touches the columns, joists, and beams. Slabs are build using steel reinforcement by laying the bars horizontally and forming a grid. So as to induce greater durability, the reinforcement in the slabs are joined with the reinforcement of the columns and beams. The concrete mixture is poured over the grid and after sufficient setting time, it becomes a hard solid mass. Slabs usually supports vertical dead loads, and live loads to great extent. Floor slabs widely use reinforcement thicknesses of 100 mm to 500 mm.

Shear walls and cladding

They form the main structural element in high-rise buildings and residential constructions. Shear walls are meant to consider the effects of the horizontal loads falling on the building due to wind forces and earthquake seismic loads. These walls are high columns having thickness of about 400 mm and length up to 30 m. These wall can also take care of vertical loads, but they are primarily meant to consider the horizontal loads in a particular direction. A two-way shear wall is relatively used to take of horizontal loads from both the directions in x-plane. To construct a shear wall, different materials are used that can induce the strength of the wall, but masonry forms the basics of such walls.

Cladding is the process of adding an additional external layer exterior to the concrete structure. Cladding is constructed to induce certain additional properties to the concrete structure like thermal insulation, water impermeability, weather insulation, or to enhance the building appearance. There are numerous materials used to construct the cladding, some them are glass, aluminum panels, stone sheets, and ceramic facades. Steel claddings are also provided on many structural components to enhance the load bearing capacity and improve the aerodynamic performances of tall buildings.

Context and Applications

This topic is taught in many undergraduate and post-graduate degree courses like:

• Bachelors of Technology in Civil Engineering
• Masters of Technology in Civil Engineering

Practice Problems

Q 1. What is the characteristics of a slab?

1. They have a hollow-core.
2. They are flat horizontal members.
3. They carry axial loads.
4. They are constructed using bricks and cement.

Answer: Option b

Explanation: Slabs are flat horizontal members that carry vertical dead as well as live loads.

Q 2. Which of the following is a material of cladding?

1. Glass
2. Girder
3. Stone sheets
4. Both a and c

Answer: Option d

Explanation: Glass and stone sheets are two of used cladding materials in building construction.

Q 3. Which of the following forms a major component in a high-rise building?

1. Concrete frames
2. Columns
3. Shear walls
4. None of these

Answer: Option c

Explanation: The shear walls form a primary component in a high-rise building.

Q 4. Which of the following components form a part of the concrete framing system?

1. Beams only
2. Both columns and beams
3. Columns, beams, joists, and slabs
4. Only beams and slabs

Answer: Option c

Explanation: Columns, beams, joists, and slabs forms the major component of a concrete framing system.

Q 5. What is the purpose of reinforced concrete?

1. It has high tensile load carrying capacity.
2. It has high compressive load carrying capacity.
3. It has both tensile and compressive load carrying capacity.
4. Reinforced concrete can carry shear loads due to seismic loads.

Answer: Option c

Explanation: Reinforced concrete are concrete mixture poured over a network of steel reinforcing bars. It allows the reinforced concrete to withstand high tensile and compressive loads.