dug out a gardening book for this one. It says when the canes have finished fruiting cut them all down to ground level. Space out and tie in the new canes up the centre and out like a fan shape, repeat the process in subsequent years. (If this goes wrong, blame Alan Titchmarsh) You can also bend down shoot tips and bury them in the soil, held in place with a peg or piece of wire. It says do this in July but you may not be too late. Eventually a shoot will emerge forming a new plant which can be detached the following spring with its own roots and planted wherever you want it.