What is the likely cause of this failure?

Using the only data available from this picture (which is the crack pattern), what is likely caused failure of this structure?

The structure is a cantilever and we expect the maximum bending moment and shear force to occur at the support (usually taken as the centreline of the column). Predictions can be made on the cause of the failure based on the nature of the crack…

Kindly let us know your view in the comment section. Thank you and God bless you.


  1. Using “x” and “y” as the vertical plane and “z” as the horizontal plane, there appears to be a high load at the cantilever end in the “z” plane (a beam in the “z” plane) causing torque in the cantilever. The cracks have not propogated through the whole section and are on the outside face of the beam. Not enough vertical bars in the cantilever reo cage.

  2. Diagonal crack failure occur as a result of absent of Z-bar and improper spacing of the links/stirrups /re-Bars which could cause failure at an angle 45degree..

  3. As I can see in the picture there are two cracks, X shape, the wider one is due to not sufficient top rebar in the cantilever and the thin crack is due to not enough stirrups.

  4. From the picture, the preventive measure to avoid creation of cracks was overlooked.
    Proper concrete mix design ,placement and vibration of concrete is yet to be applied.

  5. This form of cracking is the result of Torsional forces.
    The X-shape pattern comes from loading reversal, such as an earthquake.

  6. The major cause of fracture of the cantilever beam is insufficient counter weight at the free end of the cantilever beam. Can be redone with same reinforcement and have a parapet wall at the free end.

  7. 45 degree cracks are typical of shear failures, produced by bending and / or torsion, and are avoided by placing stirrups and longitudinal steel in the beam faces


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