Warning when tying footings with centring beams or tie beams between columns with foundations at different levels

Introducing a centring beam, carried from the footing of a column starting at the upper foundation level to a column or wall whose foundation is lower down, induces forces in this column or wall that cannot be considered, such as axial forces and moments, because the footing foundation is analysed later. This means that the upper structure is analysed first and, once the forces in the starts have been obtained, the foundation is analysed.

An iterative analysis would have to be carried out to solve the foundation. The program does not carry out this process. Therefore, although the program warns the user and allows them to continue with the sizing of the foundation, it does not consider this centring beam. In any case, if desired, users can constructively carry out what is shown in the construction detail CSZ007 to be able to disregard the induced forces. On a practical level, a column start can be entered in the program in the upper foundation group, next to the column or wall that has a foundation underneath, as if it were an expansion joint. Then, select this start as the end of the centring beam.

Naturally, the floor plan must be adjusted so that it does not show said start. The detailing of the length of the centring beam must also be altered, as it will actually be built up to the element with a foundation underneath.