Strip footings (Foundation system)
Introduction
A footing is a type of surface foundation, which can be used on reasonably homogeneous terrain and with medium or high compression resistance. They consist of a wide concrete prism (concrete) located under the pillars of the structure. Its function is to transmit to the ground the stresses to which the rest of the structure is subjected and anchor it.
When it is not possible to use footings, piling foundations "Pilot (foundation)") or foundation slabs must be used.
Types of footings
Contenido
Existen varios tipos de zapatas en función de si servirán de apoyo a uno o varios pilares o bien sean a muros. Para pilares singulares se usan zapatas aisladas, para dos pilares cercanos zapatas combinadas, para hileras de pilares o muros zapatas corridas.
Insulated shoes
Used for isolated pillars in good quality soils, when the eccentricity of the pillar load is small or moderate. This last condition is met much better in the non-perimeter pillars of a building. Isolated footings according to their relationship between depth and flight or maximum free length can be classified as:
And depending on the vertical stress in the geometric center of the footing, a distinction is made between:
The correct sizing of the isolated footings requires checking the bearing capacity of sinking, checking the state of balance (slip, overturning), as well as checking its resistance and its differential settlement in relation to the adjacent footings.
To build an isolated footing, the foundations and structures of buildings located on terrain of a heterogeneous nature, or with discontinuities, must be made independent so that the different parts of the building have stable foundations. Constructively, it is advisable that the building facilities be on the plane of the foundations, without intersecting footings or braces.
The depth of the support plane is set based on the geotechnical report, without altering the behavior of the ground under the foundation, due to variations in the water table or due to possible risks due to frost. It is advisable to reach a minimum depth below the surface level of 50 or 80 cm in those areas affected by these variables. The geotechnical report provides information on the compressive strength of the different strata, so from it it is possible to decide the most appropriate stratum taking into account the heterogeneity of the terrain and the construction cost of the various types of foundations.[1].