Originally Posted by ACustomer
They were able to replace quite large bridges on the Cork line over a weekend, why not at Oola? On 4 days a week trains are able to run through Oola so it's not as if there is some total demolition of a bridge and abutments.
It will really depend on the nature of the works. On some bridges the life expired part might be the span, on others the abutments and others the foundations. There will of course be other factors like how busy the road and railway are, ground conditions, access, working space, etc.
Replacing the span on a steel or pre-cast concrete bridge can be quite straightforward - lift one out and the other in and re-do the track. Others, like the Shannon bridge on the Sligo line will take weeks to set up, never mind to do any actual work.
It may be that they are using the current schedule to do foundation work, e.g. piles or underpinning and then when they have sufficient strength in the foundations, they can do the actual span.