Concrete ceiling beams

I have a few concrete ceiling beams which have blown due to water ingress at one end , some have another storey above them some just have the roof. I can stop the ingress of water, I can also repair them with industrial résine. Has anyone had individual beams replaced or has anyone had new beams put either side. Looking to see if it's possible before taking the route of a new roof and a lot of internal work. Thank you in advance.