The three forms of shear failure of reinforced concrete structures and their failure characteristics are discussed
Shear compression failure: when the shear span ratio is less than or equal to 1 is less than or equal to 3, occurrence of shear compression failure. The failure characteristics are appeared; flexural shear crack load, can still have a larger growth. With the increase of loading, have other flexural shear crack, which will form a main crack, said for critical diagonal crack. With the increase of load to critical diagonal crack at the upper end of the remaining section gradually reduced, finally the upper critical diagonal crack is concentrated near to the loading point, the concrete was crushed and damaged. Shear compression failure is mainly due to the remaining section of the concrete in shear interaction force, horizontal compressive stress and the concentrated vertical load at the point of local stress, although the failure did not like the diagonal tension failure as suddenly, but also belongs to brittle failure type. Compared with the diagonal tension failure, shear compression failure of bearing capacity is higher.
Diagonal tension failure: when the shear span ratio of >3, occurrence of diagonal tension failure. The failure characteristics are: diagonal cracks once appear quickly extended to the concentrated load point, the beam along the diagonal crack into two parts and sudden failure, failure surface neat, no traces of crushing, the failure load is equal to or slightly higher than the load the inclined crack. The diagonal tension failure due to tensile strain of concrete ultimate tensile strain caused by failure is sudden, belongs to brittle failure type.
Diagonal compression failure: when the shear span ratio is very small (usually is less than or equal to 1), occurrence of baroclinic destruction. The destruction is characterized in abdominal load and bearing beam between a plurality of substantially parallel ventral shear crack, with the increase of load, the beam abdomen was divided into a plurality of oblique oblique crack to the compression of the "short column", finally along the diagonal compression failure, diagonal crack damage and thick. The baroclinic destruction is very sudden, belongs to brittle failure type, the bearing capacity than the shear compression failure.
