The　large　degradation　of　the　mechanical　performance　of　hollow　reinforced　concrete　(RC)　bridge　piers　subjected　to　multi-dimensional　earthquakes　has　not　been　thoroughly　assessed.　This　paper　aims　to　improve　the　existing　seismic　damage　model　to　assess　the　seismic　properties　of　tall,　hollow　RC　piers　subjected　to　pseudo-static,　biaxial　loading.　Cyclic　bilateral　loading　tests　on　fourteen　1/14-scale　pier　specimens　with　different　slenderness　ratios,　axial　load　ratios,　and　transverse　reinforcement　ratios　were　carried　out　to　investigate　the　damage　propagation　and　the　cumulative　dissipated　energy　with　displacement　loads.　By　considering　the　influence　of　energy　dissipation　on　structural　damage,　a　new　damage　model　(M-Usami　model)　was　developed　to　assess　the　damage　characteristics　of　hollow　RC　piers.　The　results　present　four　consecutive　damage　stages　during　the　loading　process:　(a)　cracking　on　concrete　surface,　(b)　yielding　of　longitudinal　reinforcements;　(c)　spalling　of　concrete,　and　(d)　collapsing　of　pier　after　the　concrete　crushed　and　the　longitudinal　bars　ruptured　due　to　the　flexural　failure.　The　damage　level　caused　by　the　seismic　waves　can　be　reduced　by　designing　specimens　with　a　good　seismic　energy　dissipation　capacity.　The　theoretical　damage　index　values　calculated　by　the　M-Usami　model　agreed　well　with　the　experimental　observations.　The　developed　M-Usami　model　can　provide　insights　into　the　approaches　to　assessing　the　seismic　damage　of　hollow　RC　piers　subjected　to　bilateral　seismic　excitations.