Maidenhead Railway Bridge

 bridge, railway bridge

To carry the Great Western Railway across the Thames between Slough and Maidenhead, Brunel designed two spectactular semi-elliptical brick spans 128ft long with a rise of only 24ft 3in. The centre pier of the bridge rests on an island midstream. The rise of the arches needed to be low in order to accommodate the necessary navigational clearance on the river at the same time as maintaining the flat gradient Brunel had set out to sustain in the building of the railway. At the time, these were the flattest bridge arches yet built. As such they caused a deal of controversy concerning their stability. The bridge was widened on both sides by Sir John Fowler in the period 1890-3 to accommodate the quadrupling of the line. The new width is 57ft 3in, parapet to parapet. It was found that the soffits had distorted slightly with the movements in the structure since the bridge's construction, so the new work had to be built slightly out of alignment with the old in order to keep the true ellipses. To avoid differential settlement between old and new, the new foundations were close piled, covered with a wooden grillage and filled with concrete.