A stiffener for a structure submitted to tensile and/or compression and/or shear stresses, that includes a shaped section including: a contact area with an element to be stiffened having a closed cross-section and providing stability, the aforementioned area including first and second legs; and a core normal to the element to be stiffened that provides a support surface capable of element recovery, the aforementioned core being formed by one of the two legs. Application in aircraft structures.