Why are you looking at replacing? There is no reason to do so!

Because they are looking sad, and each year are giving less fruit. This season several of the plants have no canes.

Have you been cutting out the canes from the previous year?

Maybe they could do with feeding and a bit of TLC.
I would remove dead canes now, then leave them alone until March next year when I would give them some general fertiliser and mulch them with compost. You may not get much of a crop next year either because they fruit on 2 year old canes, but repeat the care regime each year and I am sure they will come up trumps for you.

Thank you for all your comments. I will do as you suggest, and hope for the best. I always thought they fruited on the previous years canes. Maybe that is where I went wrong as they have had quite a bit of TLC!

Summer fruiting raspberries do fruit on the canes that grew in the previous year. So in year one the cane grows in year two it fruits and you then cut out the canes that have fruited leaving the ones that grew to fruit the following year. Autumn fruiting raspberres are different in that they need to be cut back in early spring and fruit on that years canes.

Got the message. I must persevere, and give lots of tlc. Thanks to those who responded.