What are the additional stirrups of primary and secondary beams and what are their functions?

Generally, when the secondary beam transfers force to the main beam, it is not concentrated force transfer. Then, because the height of the secondary beam is generally lower than that of the main beam, the concentrated force is located in the middle of the main beam web, and the cross section of the main beam becomes tensile at the upper part and compressive at the lower part, resulting in splayed cracks in the main beam web below the bottom of the secondary beam. Therefore, setting additional stirrups or hanging bars at the joints of primary and secondary beams can limit the development of secondary cracks. See the design principle of reinforced concrete structure for details.

Stirrup is used to meet the shear strength of inclined section and connect the main reinforcement with the reinforcement of concrete frame in compression area. There are single-limb stirrups, open rectangular stirrups, closed rectangular stirrups, rhombic stirrups, polygonal stirrups, square stirrups and circular stirrups. Stirrups should be determined according to calculation, and the minimum diameter of stirrups is related to the beam height h, when h≦800mm, it should not be less than 6 mm; When the H> is 800 mm, it should not be less than 8 mm ... The stirrup at the beam support is generally set at 50mm from the beam side (or wall side). For reinforced concrete independent beams supported on masonry structures, the anchorage length of longitudinal reinforcement in Las should not be less than two stirrups. When the beam is integrally connected with the concrete beam or column, stirrups are not needed in the bearing.