Beam falling prevention device and modular expansion joint

The invention provides a beam falling prevention device and a modular expansion joint. The beam falling prevention device comprises a sliding plate, a base, a cover plate, a limiting plate, a supporting rod and a rotating part, the supporting rod comprises a first end and a second end, the first end is connected with the rotating part, an arc-shaped groove is formed in the other end of the base, a first opening end face is formed in the end, facing the arc-shaped groove, of the base, and a first through hole is formed in the cover plate in a penetrating mode. The arc-shaped groove and the first through hole form a spherical cavity, the rotating part can rotate in the spherical cavity, a second through hole is formed in the limiting plate in a penetrating mode, the first end penetrates through the second through hole, and a gap is formed between the first end and the second through hole. The cover plate is connected with the base, and the cover plate is used for preventing the rotating part from falling off wh