Horsestool bar is a structural form used to strengthen the internal stress of the beam caused by the increase of span and load in concrete structure. In the position where the internal stress of the beam is large, people usually set the horse stool bar to increase the number of steel bars to improve the bearing capacity and bending stiffness of the beam.

However, the horse stool tendon is generally not suitable for use as the main tendon, mainly for the following reasons:

1. The position of the horse stool bar: the horse stool bar is generally located on the upper part of the beam, which is used to increase the number of steel bars. The main reinforcement is generally located at the bottom of the concrete beam, in the tension area of the beam, which is mainly used to resist the tensile stress caused by the force to ensure the strength and carrying capacity of the beam. Therefore, the position and role of the horse stool tendon and the main tendon are different, and the horse stool tendon can not play the role of the main tendon.

2. Layout of reinforcement: the main reinforcement is generally arranged according to the design requirements and stress characteristics, and the number, diameter and spacing are determined according to the calculation results. The horse stool reinforcement is generally arranged between the main reinforcement to increase the number of local reinforcement to improve the bearing capacity of the beam. Therefore, the arrangement and function of the horse stool bar are different from the arrangement and function of the main bar, and can not be used as a substitute and as the main bar.

3. The stress characteristics of the reinforcement: the main reinforcement is generally located in the tension area of the beam and bears the tensile stress. The horse stool bar is generally located in the compression area of the beam, bearing the compressive stress. Therefore, the stress characteristics of the main reinforcement and the horse stool reinforcement are different, the main reinforcement is mainly used to resist the tensile stress, and the horse stool reinforcement is mainly used to strengthen the bearing capacity of the compression area. Because of the different stress characteristics, the horse stool bar and the main bar play different roles in a beam, and the horse stool bar can not replace the main bar.

4. Structural stability: The structural stability of the beam means that under the action of load, the beam will not lose balance and deformation is too large. The setting of the main reinforcement can increase the flexural rigidity and shear resistance of the beam and improve the stability of the structure. The function of the horse stool bar is mainly to increase the bearing capacity of the beam, enhance the compression area of the beam, and do not directly affect the structural stability of the beam. Therefore, the horse stool bar can not be used as the main bar, can not replace and affect the structural stability of the beam.

To sum up, the position, arrangement, stress characteristics and influence on structural stability of the horse stool bar are different from the main bar, so the horse stool bar can not replace the role and function of the main bar. The horse stool bar should only be used as an auxiliary structural form to strengthen the beam, increase the number of steel bars, and improve the bearing capacity and bending stiffness of the beam. In the process of beam design and construction, it is necessary to choose the main bar and horse stool bar reasonably according to the actual needs and structural requirements of the structure to ensure the stability and safety of the concrete structure.