A practical approach
As we have seen in the introduction and as we’ll see again in “types of foundations”, there is a fairly large variety of situations in a tensile structure, as far as the foundation is concerned. If we add the varied types of soil we may find in any building: clay, sand, silt, mixtures of these three, rocks, etc, we come to the conclusion that foundations of tensile buildings will be really diverse.
This is true. However, for small and medium constructions, we can see how builders clearly opt for solutions that do not complicate things a lot, that is, for solutions that they are used to apply and do not involve different technology than the usual one.
If we add the fact that to compensate for pulling loads, the safest way, since only depends on the gravity (weight), it is to use a dead weight to balance this load, we will conclude that an appropriate solution will be using reinforced concrete footings. These prismatic, square footings (when there are no bending moments or very large horizontal forces) and rectangular (if the opposite) are the usual way to found many buildings, even if they are of certain dimensions. So builders often thank this type of foundation even if it means using more concrete than with other more sophisticated solutions: anchors micropiles, piles, screws, etc.
Only in the case of a rocky soil, the use of footings obviously is not the best option. In this case we should study the soil from the geotechnical point of view: quality, depth, etc., of the rock stratum and use solutions based on direct anchors to this stratum.
It is true, however, that the similarity of these foundations with the ones we find in normal footing construction exists only in the external form. Pulling loads and bending moments and important horizontal forces, involve a very different design of the reinforced concrete, with reinforcement located in unusual positions. It’s like placing footings upside down. But not only the reinforcement: concrete itself will behave differently (tension/compression). So a common footing in tensile buildings may be very different from the typical one.
In the following sections we will find references to these differences. In the future WinTess3 will produce still more results and information on these footings and their components: reinforcement, base plates, anchors, etc.