The characteristics of internal transport barrier (ITB) structures are studied and active ITB control has been developed in JT-60U reversed shear plasmas. The following results arefound. Outward propagation of ITBs with steep Ti gradients is limited to the minimumsafety factor location ρqmin. However, ITBs with reduced Ti gradients can move to the outside of ρqmin. The lower boundary of the ITB width is proportional to the ion poloidal gyroradius at the ITB centre. Furthermore, active control of the ITB strength basedon modification of the radial electric field shear profile is successfully demonstrated by toroidal momentum injection in different directions or an increase of heating power byneutral beams.