Queen Adelaide Underbridge Strengthening

U/B ETN/1575 Queen Adelaide is a 40.75m. single span, 44 degrees skew, truss girder underbridge which carries the 2 track (non-electrified) Ely to Norwich railway over the River Great Ouse and adjacent (east side) towpath NE of Ely.

The track alignment over the bridge is straight (in plan) but set to a 'humped' vertical profile so that the bridge soffit offers acceptable headroom to the river below. The track-form over the bridge is FB rail laid on large transverse timber bearers supported off the bridge deck rail-bearers. The railway carries a mix of DMU passenger and loco-hauled freight traffic operating up to the line speed (at this point) of 45mph. The structure dates from the late 19th century and comprises wrought-iron, built-up section, structure members, chiefly 2 parallel truss girders supporting a deck of transverse cross girders and rail-bearers fixed to the cross-girder webs.

A package of strengthening works (including the installation of overhead portal frames) has been undertaken to improve the existing assessed capacities of the structural members but at the end did not achieve the Client-aspiration assessed capacity threshold. Further strengthening to achieve RA10 @ 45mph is likely to prove both expensive and very disruptive to rail operations if the truss/cross girder connection needs to be considered as either 'pinned' or 'fixed'. Structural assessment has considered the truss/cross girder connection to be either 'pinned' or 'fixed' resulting in widely differing capacities for this connection (pass as 'pinned' but seriously 'overstressed' as 'fixed' with knock-on impacts on assessed capacities for the other bridge structure members.

I have been responsible for undertaking the analysis using LUSAS and I have prepared detailed design of the connections including the strengthening of existing wrought iron plated members using close tolerance bolts to replace the existing rivets.