What are foundations?
A foundation is the set of elements of a structure whose objective is to transmit and distribute the load it supports to the ground so that it does not exceed the weight limit. Foundations are usually buried in solid soil, also called a foundation bed. Its structure aims to balance the weight and loads received, making it stable, resistant, and safe.
What is the importance of foundations?
The success of a good construction project lies in the quality of the foundations since their main value is providing security and solidity to a structure by supporting loads and anchoring them to the ground.
Based on geological and geotechnical studies prior to installing the foundations, it is possible to know which structural elements are best suited for building a structure whose load is securely distributed over the ground without exceeding the permissible pressure.
What are the main functions of foundations?
- Providing tensile or compressive stresses up to the bases, distributing the weight equally.
- Resisting the bending forces produced by the ground. To this end, they have a shell on their inner face.
- Adapting the structure to possible ground movement.
- Resisting external factors that can alter the terrain’s conditions, such as water.
- Securing the structure against horizontal forces like wind or earthquakes in order to preserve its integrity.
What types of foundations are there?
All foundations consist of two parts:
- The foundation: the structural element responsible for transmitting the building’s loads to the ground.
- The foundation ground: the area of the terrain affected by loads.
Based on this, foundations can be classified into:
- Direct or superficial: those where the width of the base is greater than the depth and the load is spread across a horizontal support. With these foundations, the soil is a significant component since it has significant load-bearing capacity. The most common are:
- Isolated footings: they serve as the basis of specific structural elements, such as pillars. They spread the support surface until the ground supports the transmitted load.
- Combined footings: their dimensions depend on the load supported, the resistance of the material to compressive stress, and input on the ground. If there are two or more pillars, it’s combined; if there are groups of three pillars that are aligned, those are continuous.
- Foundation slabs: a platform supported on the ground for transmitting loads. They usually have armor on top to reduce the counterweight of the terrain. They are used when a structure has a smaller surface area with respect to the volume of the building.
- Indirect or deep: used for very heavy structures. They are installed in deeper, more resistant areas of the soil, and the greatest load is placed on them. This type of foundation has more load capacity. The most common are:
- Piles: a type of base driven into the ground to transfer the load. They can be dug in or moved to previously excavated ground and subsequently filled with concrete.
- Slurry walls: used in tall buildings to counteract forces from the terrain, as well as to prevent their deformation. They also act to contain and waterproof the surface of the wall and limit the movements of the ground resulting from excavation.
What conditions should a foundation meet?
Foundations are generally made of simple or reinforced concrete stone materials. In addition, they are supported by a centered load since they are primarily subject to traction and compression forces.
However, foundations can also use the friction force transmitted by a surface to support horizontal and traction loads, thus holding the building firm on the ground.
All foundations must reach a load-bearing capacity and an allowable pressure, which is the maximum weight they can support and the maximum pressure they can transmit without surpassing their end limits.
They must also meet the following requirements once installed:
- Not reaching their end limits – that is, they do not go into a state of deterioration (sinking, overturning, or their structure breaking).
- Maintaining the functional and aesthetic capacity of the building – that is, the condition of its service limits is not affected.