Demodara Black Bridge steel-girder thermal expansion bearings: curved viaduct maintenance?

The Black Bridge at Demodara (Bridge No. 42 on the Main Line) is a curved steel-girder viaduct carrying broad-gauge tracks over a deep mountain river ravine immediately before entering the spiral loop tunnel. Because ambient temperatures fluctuate widely between chilly nights (14°C) and hot sunny afternoons (35°C), the long structural steel spans experience significant longitudinal thermal expansion and contraction. One end of each girder span is anchored firmly to stone abutments, while the opposite end rests on heavy cast-steel roller rocker bearings. SLR bridge inspectors grease roller beds quarterly to ensure spans slide freely without inducing lateral buckling forces into stone masonry piers.