The anchorage length in the foundation is as important as in other types of structural elements. The length required to transfer the stress from the reinforcement to the concrete is called the anchorage length.
The anchor length is generally calculated from the tension rod.
The design tie length or anchorage length can be calculated as described in the Design Anchorage Loop Length article.
Furthermore, anchor length and overlap length are more closely related. We first calculate the anchorage and then determine the overlap length. For more information, see the Overlap and Anchor Length article for more information.
The following figure shows the reinforcement of the foundation in detail.
As shown in the figure above, the length between the surface of the column and the edge of the foundation is taken into consideration to decide whether the foundation reinforcement needs to be bent at the end.
When
The distance between the surface of the column and the edge of the foundation is less than the anchorage length. In this case, the foundation reinforcements must be doubled.
There are not many calculations available to verify the requirement to be.
Consider the following example.
- Foundation Size: 900mm x 900mm
- Column size 250x250mm
- Assume the column and base have the same coverage
- Suppose the foundation reinforcement is T10 bars
Distance between the surface of the pillar and the edge of the foundation = (900-250)/2 = 325 mm
Required anchor length = 44 x 10 = 440mm (as per BS 8110)
The existing length is therefore not sufficient to anchor the reinforcement. Therefore, the reinforcement must be bent upwards to the required length.
The following numbers are from the Standard Method of Detailing to provide a clear indication of the finish of the reinforcement in accordance with the provisions of Eurocode 2.
If the reinforcement does not bend, the figure above can be used. However, if the situation is worse, we need to do the detailing as shown in the figure.
It should be noted that the pillar reinforcement must have a horizontal curvature of 450 mm in length, as specified in the detailing guideline.
You can also consult the following articles published in the same subject area.
- Design of individual foundations
- Foundation reinforcement details
- Designing combined foundations
- Strip foundations design
