Modular expansion device for bridge

The invention relates to a modular expansion device for roads and urban highway bridges. The expansion device is characterized in that compression control springs of a displacement control system are in a forward-backward pairwise arrangement, the structure characteristic of which is characterized in that the compression control springs are distributed between a displacement case and support hangers and between support hangers, a backward compression control spring, a forward compression control spring and a backward compression control spring, or a forward compression control spring, a backward compression control spring and a forward compression control spring are distributed sequentially in the gap between edge joist steel and center joist steel from the left to the right along a cross beam; and on both sides of the cross beam, if a backward compression control spring is arranged on the front side, a forward compression control spring is arranged on the back side. The modular expansion device has strict de