Most　of　vibration-based　damage　assessment　methods　require　modal　properties　that　are　obtained　from　temporal　signals　through　the　system　identification　such　as　the　Fourier　transform　(FT).　The　modal　properties　such　as　natural　frequencies　and　mode　shapes　were　poor　indication　of　damage.　The　wavelet　packet　transform　(WPT)　is　a　mathematical　tool　that　has　a　special　advantage　over　the　traditional　Fourier　transform　in　analyzing　non-stationary　signals.　It　adopts　redundant　basis　functions　and　hence　can　provide　an　arbitrary　time-frequency　resolution.　In　this　study,　a　damage　detection　index,　wavelet　packet　energy　rate　index,　is　proposed　for　the　damage　detection　of　tested　beams.　Dynamic　signals　measured　from　tested　beams　are　first　decomposed　into　wavelet　packet　components,　then　wavelet　energies　rate　index　is　computed.　Three　damage　scenarios　were　conceived　to　validate　the　applicability　of　proposed　energies　index.　The　results　demonstrated　that　the　WPT-based　energies　rate　index　is　good　candidate　indices　that　are　sensitive　to　structural　local　damage.