Updated: Jul 2, 2020
How a tied-arch Work?
Thrust arches rely on horizontal restraint from the foundations. The vertical and horizontal reactions resolve into a force along with the arch members.
The ends of the arches are normally pinned. This will be the most satisfactory solution when the arch bears onto good foundation material such as competent rock.
However, the horizontal reactions lead to heavy uneconomic foundations.
The tied-arch offers a solution that the deck can be arranged in different desirable levels since it can carry the horizontal force as a tie member.
Loading of the hangers
Thrusts downwards on a tied-arch bridge deck are translated, as tension, by vertical ties such as steel wire hangers between the deck and the arch. This loads then develop thrust in the arch which is balanced by tension in the tie of the deck and the arch member.
The arch the deflects down and the loads are transmitted to the foundation supports with the free end absorbing all the movement such as temperature breaking loads and general live loads of the bridge.