- Definition of foundation.
- types of foundations
- flat foundation
- insulated foundations
- combined foundations
- belt shoes
- shoes mate
- deep foundations
- foundation pile
- Dockfundament (Box)
- flat foundation
definition of foundation
Foundations transmit forces from structural systems to an external source, usually the soil. The floor is essentially infinitely stable, making it a great place to transfer loads from your structure.
In a structural model, the foundation is often represented assupportsor boundary conditions. They act as an endpoint for a load path.
Foundations serve several purposes, including:
- Stabilize and maintain structure in the short term.
- Supports long-term differential settlement and extends the life of the structure.
- Distribute support loads over a larger area.
- Redistribute uneven structural loads.
- Protect the structure from soil erosion below the foundation.
- Support lateral stability against lateral loads such as wind and earthquakes.
The ground on which the foundation sits or is placed is a critical aspect of foundation design and must be analyzed and checked for stability. Different types of soil, such as clay, behave quite differently from others, such as sand. These differences in behavior are expressed by physical quantities such as soil cohesion and friction angle.
types of foundations
Foundation systems are generally divided into shallow foundations and deep foundations. Shallow foundations are almost always poured into the ground. The site is relatively excavatedsatindepths, subterranean heights. They are easier to build, less expensive, and therefore generally a more popular design choice for smaller structures.
Figure 1: Foundation systems
Difference between 'Fundamentals' and 'Fundamentals'
The terms foundation and footing are often confused with each other.
A "foundation" is a general term used to describe a part of a structure that transfers the load from the superstructure to the supporting floor. It can be classified as shallow or deep foundation.
A "base" is part of a foundation in contact with the ground. Foundations are usually only associated with shallow foundations. See foundation system diagram above. All foundations are considered foundations, but not all foundations are foundations.
Difference between deep and shallow foundations
Shallow foundations are mainly used where the load is transferred to a supporting soil located on asatindepth (as little as 1 meter or 3 feet). Deep foundations are used when the load is transferred to deep strata (from 20 to 65 meters or 60 to 200 feet).
Deep foundations are most often found in places with unfavorable soil conditions. For example, most offshore projects use deep foundations for greater stability. The process of building a deep foundation is more complex and expensive. It requires heavier equipment, specialized labor and proper time management. Deep foundations can be driven into the ground or driven into the ground, the ground is much harder to dig and the ground pressure increases the deeper you go. A deep base provides lateral support, resists lifting and supports heavier loads. It is based on both final rolling friction and surface friction.
In comparison, shallow foundations are less expensive and require less labor, equipment and materials. They are mainly based on final support on the ground. Reinforcement in shallow foundations helps resist toppling and foundation bending.
insulated foundations, also known as spread or cushion foundations, are the simplest and most common type of foundation. Each foundation supports its column from which it takes the load and distributes it to the ground on which it rests. Support shoes are almost always square or rectangular. This makes them easier to parse and create. Foundation dimensions are estimated based on column loads, safe bearing capacity and excessive soil settlement.
Figure 2: Isolated foundation
Wall foundations, also called strip foundations, support the weight of structural and non-load bearing walls. Similar to isolated foundations, the larger the foundation area, the greater the foundation's ability to limit settlement. Strip foundations are useful for supporting load-bearing walls because they support not only the permanent structure loads, but other design loads as well. Wall foundations are also cast in plain or reinforced concrete and are sometimes prefabricated before being brought to site.
Figure 3: Wall foundation
As isolated foundations, thecombined footIt is built when columns support structural loads. This is used when two or more columns are so close together that their isolated foundations overlap. Construction of combined foundations can be more economical when the foundation materials (concrete) are cheaper than the labor to form two separate foundations. Combined foundations can be rectangular, trapezoidal or T-shaped, depending on the size and location of the columns supported by the foundation.
Figure 4: Combination base
Purlin foundations, also known as cantilever foundations, are two isolated foundations connected to a purlin beam.
Purlin beams usually connect two foundations that support columns that resist significant lateral forces. The center purlin support helps reduce the effects of lateral loads without adding additional gravity pressure to the ground that would occur if a combination foundation were used.
Figure 5: Belt base
As the name suggests, a track foundation, also known as a raft foundation, is a type of foundation that extends from columns or walls fully into the structural area of the building, much like a floor slab. It is most commonly used in basement construction, where the entire basement slab serves as the foundation. The carpet base is chosen when the building is supported by weak soil. As a result, construction loads are distributed over an extremely large area. This avoids the different settlements that would prevail with isolated foundations. This is more appropriate and economical to use when the building's footprint is relatively small or columns are close together, limiting material costs. On the other hand, carpet foundations are undesirable for structures where groundwater is above the load-bearing surface of the soil.
Figure 6: Estera or raft base
The objective of any type of foundation is to transfer loads or forces from the superstructure to the soil without excessive settling. Pile foundations are commonly used for projects located in depths of weak or saturated soil where the excavation depth is not feasible for shallow foundations. The stakes vary in diameter but are much deeper than they are wide. The load of the superstructure is transferred from the piles through poorly compressible soil layers to harder soils or hard rock. They can be made of steel, wood, in-situ concrete or precast concrete. Cast-in-place piles are made by digging a hole in the ground with a long rotary drill and filling that hole with steel and concrete reinforcement. When well walls fail to support themselves, steel casings can maintain the shape of the well. The prefabricated piles are driven into the ground perpendicularly or at an angle to the vertical using a ram hammer attached to heavy machinery. Sometimes the piles are connected at their highest point to a foundation block, essentially a single foundation, to form a pile set that can support a large column (see Figure 7).
Advantages of using pile foundations:
- Piles can be prefabricated to any required specification or design requirement in a controlled environment.
- Prefabricated piles are delivered to site and can be installed immediately, resulting in faster job progress.
- Cast-in-place piles can support large, tall structures such as skyscrapers where a shallow foundation would not suffice.
- Driven piles can also be used where drilling is not advisable due to water table pressure.
- Pile foundations can be used where soil conditions make other types of foundations impossible.
Disadvantages of using pile foundations:
- Concrete piles must be adequately reinforced to withstand the stresses when driven into the ground.
- Planning and equipment are essential for proper handling and driving of piles into the ground.
- Ground lifting or an already driven pile can occur when a pile with poor or poor drainage quality is driven into the soil.
- Pile driving creates vibrations that affect the integrity of adjacent structures.
Figure 7: Pile foundation and pile head
Foundation of the Dock (Cajon)
Pillar or box foundations are similar to single pile foundations, but with a larger "pile" column diameter. Caisson foundations are also installed differently. Unlike pile foundations, pillar foundations are built by digging or dredging the soil below ground and filling it with concrete and steel rebar. Caissons can also be drilled into bedrock or supported in layers of soil, but a "bell-shaped" cross section is required to distribute the load over a larger area (as shown in Figure 8). Due to the presence of water, pillar foundations rely on end supports to resist superstructure loads, unlike pile foundations which transfer loads through end supports and surface friction. Pile foundations are normally installed where there is no solid strata at an accessible depth, and pile foundations are often used when the topsoil consists of decomposed rock or hard clay.
Figure 8: Column or drawer foundations with guide cover
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