In the cast-in-place reinforced concrete structure system, it is a common practice to set structural columns under cantilever beams, which are mainly used to strengthen the structure and restrain the deformation of the retaining wall under cantilever beams. Cantilever beam is usually the main stress component in balcony and verandah of a building, and there is no vertical force-transmitting structural component under the beam, so the main stress reinforcement of cantilever beam is the upper reinforcement of the beam.
If the constructional column under the cantilever beam is constructed synchronously with the stressed members such as the cantilever beam, due to improper operation of the construction method, the constructional column and the cantilever beam are often cast in situ, resulting in the constructional column becoming the vertical stress fulcrum of the cantilever beam. First, the constructional column can't bear the vertical load transmitted by the cantilever beam because of its small cross section and less reinforcement. Secondly, the stress on the steel bar of the cantilever beam has also changed, from the original upper steel bar to the lower steel bar, which completely violates the design principle.