This paper presents research on 13 beams with nonprestressed and prestressed helical rib steel wire bonded in sawed grooves in the concrete cover under monotonous loads based on the lack of old strengthening methods. The prestressing, stressing process, first-crack load, steel-yielding load, ultimate load at failure and deformation are systematically studied. The results from the tests show that this new strengthening technique using helical rib steel wire bonding in the concrete cover is an efficient method, which can overcome the problems with peeling of the strengthening material when the surface bonded FRP laminates, also overcome the shortages of nonprestressed beams. The prestressed beams exhibited higher first-crack load, higher steel-yielding load, as well as a larger deformation capacity as compared to nonprestressed strengthened beams, which is important for a construction's lifetime; the fatigue behavior will improve and as a consequence the crack widths will be smaller, which can result in increased durability, which should indicate a more advantageous behavior in the service limit state (SLS). However, the ultimate load at failure is as high as nonprestressed beams, but in relation not as large as for the cracking and yielding. The ultimate load at failure is also higher as compared to non strengthened beams. The results provide a reference for engineering application.