The　excessive　enhancement　of　rotational　stiffness　leads　to　an　uneven　distribution　of　rotational　stiffness　across　the　entire　timber　frame.　This　uneven　distribution　concentrates　the　load　effect　on　the　strengthened　mortise–tenon　joints　(MJs),　causing　localized　failure　in　advance.　To　address　this　issue,　a　reversible　and　non-destructive　strengthening　method　for　the　damaged　MJs　is　devised,　involving　the　utilization　of　an　assembled　spring-steel　hoop.　The　rotational　stiffness　of　a　strengthened　MJ　is　derived　from　the　springs　that　link　the　steel　hoop　of　the　beam　and　column,　resembling　the　rotational　stiffness　of　an　intact　MJ.　A　comparison　of　the　measured　moment-rotation　curves　of　various　types　of　MJ　reveals　that　the　rotational　stiffness　similarity　necessitates　the　strengthened　MJ＇s　yield　moment　and　ultimate　moment,　along　with　the　associated　rotation　angles,　to　closely　resemble　those　of　the　intact　MJ.　Secondly,　a　design　methodology　is　developed　for　the　assembled　spring-steel　hoop,　which　involves　determining　the　parameters　of　the　connecting　spring.　The　comparative　analysis　of　the　hysteretic　test　results　on　multiple　strengthened　and　intact　MJs　indicates　that　the　strengthened　MJs　exhibit　rotational　stiffness　deviations　of　less　than　12.2　%　during　the　elasticity　stage　and　6.6　%　during　the　plasticity　stage,　in　comparison　to　the　intact　MJs.　A　spring　exhibits　a　lower　ultimate　extension　compared　to　timber,　leading　to　a　maximum　discrepancy　of　37.5　%　in　the　ductility　coefficients　between　the　strengthened　MJs　and　intact　MJs.　The　strengthened　and　intact　MJs　display　similar　patterns　of　stiffness　reduction　and　energy　dissipation　progression.　©　Elsevier　Ltd