Foundations transfer forces from structural systems to some external source, typically the ground. The ground has essentially infinite stability, which makes it a great place to transfer the loads of your structure.
In a structural model, foundations are often represented as Supports, or boundary conditions. They act as an endpoint for a load path.
The soil where the foundation sits, or is piled into, is a critical aspect of a foundation’s design and must be analyzed and checked for its stability. Different soil types such as clay behave very differently to others such as sand.
Generally, foundation systems are divided into shallow and deep foundations. Shallow foundations are almost always cast against the earth. The site is excavated to relatively shallow depths, underneath the ground elevation. They are easier to construct, cheaper, and, therefore, usually a more popular design option for smaller structures.
Shallow foundations are used primarily when the load will be transferred into a bearing soil located at a shallow depth (as little as 1 meter or 3 feet). Deep foundations are used when the load is transferred into deep strata (ranging from 20-65 meters or 60-200 feet).
Deep foundations are more commonly found on sites where the soil conditions are unfavorable. For example, most marine projects will use deep foundations for additional stability. The process of constructing a deep foundation is more complex and costly.
It requires heavier equipment, skilled labor, and proper time management. Deep foundations can be driven into the ground or cast against the earth, soil is much harder to excavate, and soil pressure increases as you go deeper. A deep foundation provides lateral support, resists uplift, and supports larger loads. It relies on both end bearing and skin friction.
The purpose of any foundation type is to transmit loads or forces from the superstructure to the ground without excessive settlement. Pile foundations are commonly used for projects that lie on weak or saturated soil depths where the excavation depth is not feasible for shallow foundations.
As the name implies, a mat foundation, also known as raft foundation, is a type of foundation spread entirely across the area of the building supporting heavy loads from columns or walls, similar to a slab on ground. It is most often used with basement construction where the entire basement floor slab acts as the foundation. Mat foundation is chosen when the building is supported by weak soil.
Thus building loads are spread over an extremely large area. This prevents differential settlement that would be prevalent with isolated footings. This is most suitable and economical to use when the building footprint is relatively small or if columns are close together, limiting material cost. Conversely, mat foundations are not desirable to construct when the groundwater is located above the bearing surface of the soil.
Ordinarily, final architectural design as well as a soil test is required for our structural design team to provide the client with a foundation design.
A framed structure in any material is one that is made stable by a skeleton that is able to stand by itself as a rigid structure without depending on floors or walls to resist deformation. Materials such as wood, steel, and reinforced concrete, which are strong in both tension and compression, make the best members for framing. Masonry skeletons, which cannot be made rigid without walls, are not frames.
The heavy timber frame, in which large posts, spaced relatively far apart, support thick floor and roof beams, was the commonest type of construction in eastern Asia and northern Europe from prehistoric times to the mid-19th century. It was supplanted by the American light wood frame, composed of many small and closely spaced members that could be handled easily and assembled quickly by nailing instead of by the slow joinery and dowelling of the past.
Construction is similar in the two systems, since they are both based on the post-and-lintel principle. Posts must rest on a level, waterproof foundation, usually composed of masonry or concrete, on which the sill (base member) is attached. Each upper story is laid on crossbeams that are supported on the exterior wall by horizontal members. Interior walls give additional beam support.
Our team of experienced and expert structural engineers will deliver a suitable design for your project that meets the codes and standards of code applicable to your particular needs and locality where you are building.