Bearing refers to the device for supporting the engineering structure and transmitting force. According to the mechanical performance, it can be generally divided into (1) fixed hinge bearing, which can adapt to the rotation of the supporting end of the structure but can not move, and can bear the force in any direction, but can not bear the bending moment; (2) The movable hinge bearing, referred to as movable bearing for short, can not only bear the rotation of the bearing end, but also move horizontally, and can ensure the free deformation of the structure under the action of temperature or shrinkage and creep of concrete, and only bear vertical force without horizontal force or bending moment; (3) Fixed support, the supporting end can't rotate or move, and can bear bending moment or force in all directions.