Concrete Frame Structures: Concrete frames are probably the most the used structural system worldwide. This kind of building is made of frames of concrete. Horizontal members are called beams, and vertical elements are columns. Between the beam, there is a flat plane of concrete called slab, where humans walk on.
Load is transferred from the slab to the beam, and then to columns that takes all the loads to the foundation system. Therefore, columns are considered the main load-carrying elements; any damage in a column would affect the entire building. On contrary, if a beam or slab was damages, it will only affect one floor.
Our calling for concrete usually refers to the reinforced concrete frames. Reinforced concrete is concrete that contains steel bars. This combination works very well because concrete is very strong in resisting compressive forces, is relatively simple to construct on-site, and is relatively affordable, while steel is extremely strong in tension. To construct reinforced concrete, one must first create a mould, referred to as formwork, that will confine the liquid concrete and provide it with the desired form and shape. Then, utilizing the structural engineer’s designs, one inserts the steel reinforcing bars and secures them with wire. Due to the shape of the tied steel, it is referred to as a reinforcement cage.
Table of Contents
Concrete Frame Structures
Type of Framed Concrete Structures
1. Rigid Frame
These frames are constructed on-site and may or may not be monolithically poured. They give increased stability and efficiently resist rotation. A rigid frame has the benefit of including positive and negative bending moments throughout the structure as a result of the connection between columns/walls, beams, and slabs.
2. Braced Frame
This frame construction resists lateral stresses by the bracing action of diagonal elements. By putting diagonal structural elements between the rectangular areas of a structural frame, the structure is braced. Compared to rigid structural frames, braced structural frames are more efficient in resisting the lateral loadings.
Types of Loads
The loads that may occur within a structure include:
- Dead Loads: the downward force acting on the building caused by the structure’s weight, which includes structural parts, walls, and facades.
- Live Loads: the downward force acting on the structure caused by the anticipated weight of the people and their goods, such as furniture and books. Typically, these loads are defined in building regulations, and structural engineers are responsible for designing structures to withstand these or higher loads. These loads will vary according to the space’s intended purpose, such as residential, office, or industrial, to mention a few. It is usual for regulations to demand a minimum live load of around 200 kg/m2 for residential, 250 kg/m2 for offices, and 1000 kg/m2 for industrial. These live loads are sometimes referred to as imposed loads.
- Dynamic Loads: These are the loads generated by traffic on bridges and related structures, and include braking and acceleration loads..
- Wind Loads: This is a critical design consideration, particularly for tall buildings or structures with a big surface area. Buildings are not intended to withstand ordinary wind conditions, but rather to withstand high wind conditions that occur around once every 100 years. These are referred to as design windspeeds, and they are required by construction rules. A building is often needed to withstand a wind force of 150 kg/m2, which is a substantial force when multiplied by the structure’s surface area.
- Earthquake Loads: During an earthquake, the Earth shakes the structure forcefully both horizontally and vertically. This may result in the building collapsing. The more massive the structure, the greater the force acting on it. It is critical to remember that both wind and earthquake produce horizontal forces on the structure, in contrast to the gravity forces it ordinarily resists, which are vertical.
Elements of Concrete Frames
Columns are a critical structural component of a frame structure. They are the vertical elements that transmit the loads transferred from the beam and upper columns to the footings.
- Main Beams – Transmit its load from the floor and secondary beam directly to the columns.
- Secondary Beams – Transmit floor loads to the supporting main beams.
A slab is a horizontal flat surface that is used to protect the structure from the elements and offer shelter for its occupants. These are the plate elements that are generally used to carry weights through flexure. They are often used to transfer vertical weights.
Due to their high moment of inertia, they may carry significant wind and earthquake forces and subsequently transmit them to the beam when subjected to horizontal stresses.
Shear walls have a critical structural role in high-rise structures. Shear walls are simply extremely huge columns – they might easily be 400mm thick by 3m long – which gives them the appearance of walls rather than columns. Their purpose in a structure is to assist in mitigating horizontal forces such as wind and earthquake loads. By definition, structures are susceptible to vertical loads caused by gravity. Vertical loads are also carried by shear walls. It is critical to remember that they are only effective against horizontal loads in one direction – the axis of the wall’s long length. Generally, they are not necessary in low-rise constructions.
Elevator Shafts are vertical boxes that contain elevators; typically, each elevator is encased in its own concrete box. Additionally, these shafts are excellent structural features, assisting in resisting horizontal stresses and bearing vertical loads.
The foundation’s main purpose is to convey the load generated by the upper columns to the solid ground.
Walls in concrete structures
Cladding of concrete frames
Concrete frame construction is a form of building that utilizes a network of columns and beams to properly transmit loads from the structure to the base. It serves as the building’s structural skeleton, supporting additional parts such as the floors, roof, walls, and claddings.