What is the Basis?

The foundations are the normal force, moment, etc. of the columns or curtains on the lowest floor of the structure. they are the elements that transfer their load to the floor. Columns or curtains cannot be placed directly on the floor. If these sections are placed directly on the floor, the strength of which is very small, they create stresses on the floor well above the normal strength of the floor, and the column is fixed by punching(drilling) the floor.

In order to reduce the stress on the ground, we need to enlarge the area because the force is constant, as can be seen in the [σ=F/A] correlation that we saw in the strength course. Therefore, between the lower end of the columns and the floor, elements such as decking, beams are made, the cross-sectional area of which is much larger than the cross-section of the column.

Another important goal is to keep the subsidence (seating) that may occur on the floor under the column or curtain at a limited level and prevent damage to the superstructure from different seating.

What are the Main Types?

We can examine the types of foundations in two main headings as “Superficial (Shallow) Foundations” and “Deep Foundations”.

What are the Main Types of Superficial (Shallow)?

• Singular(Individual) Foundations
• The Basics of Under-The-Wall
• Unified Basics
• Continuous (Continuous, Ribbon) Foundations
• Radiated Foundations

What are the Types of Deep Foundation?

• Foot Basics
• Pile Foundations
• Caisson (Well, Box) Foundations

Superficial (Shallow) Basic Varieties

Singular(Individual) Foundations

It is created by making a reinforced concrete shoe much larger than the column section under the columns. In order for it to transfer the earthquake force, the lugs are connected to each other by a tie beam or a slab with a thickness of at least 15 cm. The singular foundation is used in buildings that are low in height but long and in normal structures on very solid ground. The apartment type is not suitable for high-rise structures, because there are different risks of seating.

The Basics of Under-The-Wall

It is created by making a reinforced concrete beam at least 20 cm wider than the wall under the foundation walls of simple masonry structures.

Combined (Combined) Foundations

If the two columns are too close to each other, a single shoe (sömel) is made for both columns. By making the lug wider on the side of the column with a high axial force, it is ensured that the stress distribution formed on the ground is uniform everywhere under the lug.

Continuous (Continuous, Ribbon) Foundations

They are the foundations that transfer the loads from the bearing elements to the ground with sufficient rigidity by arranging beamed or non-beamed plates under the vertical bearing elements in one or more directions.

Continuous Foundations in One Direction

A reinforced concrete beam with an inverted table is made under the columns lined up along each axis of the structure in one direction. Column loads are transferred to the beam, from the beam to the table (lug), from the table to the floor. The cross sections of the columns determine the beam width. It is usually not suitable for apartment-type high-rise structures.

Continuous Foundations in Two Directions

A reinforced concrete beam with an inverted table is made under the columns lined up along each axle of the structure in both directions. It is generally suitable for high-rise buildings of apartment type.

Radiated Foundations

It is a type of foundation where the ground is very weak or varies from place to place, where the structural loads are excessive, and all the vertical bearing elements of the structure are placed on a single foundation. The risk of different seating on the radial foundations is very low. The radial foundation is the most suitable type of foundation for high-rise structures of the apartment type, on weak floors.

Rafter Foundations without Beams

A thick plaque is made under all the columns of the structure, covering the entire construction site, and the columns are placed directly on this plaque. The thickness of the plaque is at least 30 cm. In normal apartment-type buildings, the thickness of the plaque is approximately 8-10 times the number of floors. Especially the corner columns are risky in terms of punching. It is mandatory to determine the thickness of the plaque so that there is no punching.

Rafter Foundations with Beams

A plate covering the entire construction area is placed under all the columns of the structure, and beams are made on top of the plate, and the columns are placed on the beams, creating a rafter foundation with beams. The thickness of the plaque is at least 20 cm. It is more labor-intensive than a non-girder frame.

Types of Deep Foundations

Foot Basics

If the risk persists, the necessary calculations are made and the foot foundations are dug up to the solid ground and the foot foundations are placed on the solid ground. The foot foundations should be connected to each other with reinforced concrete beams at the top.

Pile Foundations

On very weak floors, a platform is created at ground level on top of the piles that are nailed or drilled and poured in place until solid ground is reached, and the columns are placed on this platform. Building loads are transmitted to the ground either by end piles or by lateral friction. These piles are connected to each other with reinforced concrete beams or slabs at the top. Reinforced concrete, steel and wooden types of piles are available. The cost of pile foundations is very high.

Caisson (Well, Box) Foundations

Caisson foundations are used on very weak soils or in water, where it is inconvenient or insufficient to make pile foundations. The caissons, which can be made of reinforced concrete, steel or wood with a small wall thickness, a large diameter ring or a hollow prism, are immersed in the ground or water up to the solid ground by various methods.

New elements are placed on top of it until solid ground is reached. The inside is filled with material and the base platform concrete is poured. Reinforced concrete elements are also made by pouring in place and draining the soil inside and sinking it. The cost is very high. It is applied in bridge and port construction.