You might have seen circular like structure. Infact they are the arches. The arch bridge are structurally more safe and strong in comparision to the beam frame structure bridge. Inother hand, the shear stress is reduced on the members as they are transfered to the axis and hence it reduces the shearing moment on the structure. The load applied dont produce much deflection as the typical bridge does. The bending moment is reduced which ultimately makes the calculation and structure analysis more easier. There are different types of arch structure and some of them are two hinged, three hinged structures.
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From @milanpaudel