Introduction of Pile Cap:

• The pile cap is a type of thick concrete mat-like structure which rests on the pile (timber or concrete) which gives a stable foundation to the whole system.
• This concrete pile cap transfers the entire load of the superstructure to the into the piles, which gives you a stable bearing capacity.
• The similar structure of the pile cap is a raft foundation, where there is also a concrete block-like structure is constructed.

Pile Cap Design: 

1. Suppositions in the Pile Cap Design

• The pile cap is must be rigidly set to the structure.
• Though piles are slight elastic column, that's why some distortions will be found, and we need to measure those in the plan.
• The heads of the pile are pivoted to the pile cap to provide safety from the bending moment occur in a pile.

2. Limitations of Pile Cap Designing

• Shape and form of the pile cap.
• Quantity of steel is used in the pile cap.
• Reinforcement placing in the pile cap.
• Depth of pile.

3. Characteristics of Pile Cap Designing

• The dimension of the pile is considered by the overhanging portion of the pile cap is not less than 100 mm, it would be highly preferable if you provide 150 mm.
• The thickness of the pile cap is needed to be higher because the reinforcements of columns may come out and overlay to the reinforcement of the pile cap.
• In pile cap construction, the clear cover must be more than 40 mm.
• The pile cap's span to thickness ratio must be not excess than 5. The pile cap must be relatively rigid to transfer the load to the pile section to downwards.
• The thickness must not be below 500 mm, and it's decreased to the 300 mm on the peripheries.
• The pile must not less than 50 mm into the pile cap.
• The upper coarse of pile cap is not less than 75 mm thick concrete.

Pile Cap Construction:

• The pile cap is a mat-like structure which is made of cement, sand and small aggregates.
• This mixture is placed in the required place, and it is supported by the framework to resist the whole structure from sagging and crack, this entire process is termed as shuttering and reinforcing.
• In a pile, cap reinforcements are placed in the longitudinal section of the pile cap, and it creates a wire type of reinforcement.
• At first, the reinforcement cage is placed in the pointed place; then the framework is done by timber to hold the wet concrete.
• After the concrete has placed then the most vital job is to remove the air bubbles from the concrete; otherwise, the concrete gets porous, and it may be weaker.
• After concrete placing, compaction and finishing happen then the concrete starts its internal reaction and it generates a lot of amount of heat that's why we need to cure the concrete by the water curing process.
• In the vast amount of concrete placing, there is a coolant that is used to reduce the heat, which is produced by hydration is called refrigerant coolant.
• So, these are those actions which are very useful during the construction of the pile cap.

Piles Structure:

1. Pile foundation is used when the subsoil is weaker, but the superstructure load is too heavy to carry that by shallow footing, then we use a pile foundation structure.
2. When the structure load is too heavy like a bridge, water tank, high rise building, etc., we need to use a pile foundation.

1. End-bearing Pile: In this type of pile, the end portion of this pile rests on the hard starts below the ground. In this type of pile is acting as a vertical column.
2. Friction Pile: when the structural load is too heavy, but the subsoil is not too hard, and we can not find hard strata in a reasonable depth, then we need to use friction pile. This type of pile dia is too large because to increase the surface area for the friction.

Pile Cap Foundations:

1. Shape and Size of Pile cap

• Tension reinforcement has a large radius bend.
• Make sure that enough reinforcement cover.
• Must satisfy construction tolerance.

2. Depth of Pile Cap

• Shrinkage of clay
• Shear capacity of the pile cap
• Pile anchorage
• Natural condition like frost attack
• The water table of the ground surface

Square Piling Caps

• The square pile cap is one type of popular pile cap structure.
• In this pile cap structure, all the piles are situated in a combined and compacted way.
• The square pile cap is provided when the number of piles is even; it may be four, six, eight etc.
• The square pile cap is highly used in bridge structure, high rise building, etc.

Pile Cap Reinforcement

• Pile cap reinforcement and it's calculation is one of the most essential things in the pile cap section.
• Before starting the main calculation, we need to find out the main volume of the pile cap that is (length x breadth x height)
• Bar bending schedule table for reinforcement:

• In pile cap designing, we use reinforcement cage; it increases the strength of vertical concrete column when the soil condition is not good.
• In the case of the prefabricated pile, the piles are directly placed in the site, and then the pile cap reinforcement works are done.

Pile Cap Design

Piles Structure

Pile Cap Design Example

Concrete Piles

Pile Cap Foundations

Pile Cap Formwork

Pile Cap Reinforcement

Pile Caps

Pilecap

What Is Pile Cap?

Pile and Pile Cap

Concrete Pile Caps

Pile Cap Details

• Reinforcement: Pile caps are typically reinforced with steel bars or mesh to provide additional strength and prevent cracking. The reinforcement is typically placed in both the top and bottom of the pile cap.
• Pile layout: The layout of the piles is an important factor in the design of a pile cap. The spacing, size, and number of piles are all taken into consideration when designing the pile cap.
• Size and shape: The size and shape of the pile cap are determined by the loads that it will be supporting. The pile cap is typically designed to be larger than the column or wall it supports, and it is often rectangular or square in shape.

Pile Cap Meaning

Pile Cap Reinforcement Details

• Main reinforcement: The main reinforcement bars are placed in the bottom of the pile cap and are designed to carry the majority of the load. The number, size, and spacing of the bars depend on the loads that the pile cap will be carrying and the soil conditions.
• Top reinforcement: Top reinforcement bars are also included in the pile cap to provide additional strength and prevent cracking. These bars are typically placed in a grid pattern and are designed to resist bending and shear forces.
• Stirrups: Stirrups are used to hold the main and top reinforcement bars in place and provide lateral support. They are typically placed at regular intervals along the length of the main reinforcement bars.
• Hooks and bends: Hooks and bends are used to connect the reinforcement bars and ensure that they are properly anchored to the concrete. These details are critical in preventing the reinforcement bars from slipping or pulling out of the concrete.

Types of Pile Cap

• Triangular (for 3 piles).
• Hexagonal (for 6-7 piles).
• Rectangular (for all other number of piles).

• Foundation Structure
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