Shape　memory　alloy　(SMA)　dampers　are　known　for　their　efficacy　in　eliminating　post-earthquake　residual　deformations　for　the　protected　structures.　However,　an　excessive　elongation　demand　would　deteriorate　the　self-centering　capability　and　may　even　lead　to　the　rupture　of　SMA　components.　This　means　that　severe　earthquakes　may　cause　SMA　dampers　to　malfunction.　However,　the　efforts　paid　on　addressing　this　concern　are　relatively　limited.　As　such,　this　paper　proposes　an　enhanced-deformability　SMA　damper,　which　is　a　parallel　combination　of　SMA　bars　and　friction　plates　through　geared　transmissions.　Firstly,　the　configuration,　working　mechanism　and　restoring　force　model　of　the　damper　are　presented.　And　then,　one　reduced-scale　specimen　was　fabricated　for　proof-of-concept　tests.　The　testing　results　confirmed　that　the　proposed　damper　had　an　enhanced　elongation　capacity,　i.e.,　the　damper　could　sustain　a　larger　displacement　than　the　SMA　bars　could.　After　that,　one　benchmark　frame　building　was　selected　for　discussing　the　effects　of　enhancing　elongation　on　seismic　responses　of　the　protected　structures.　Nonlinear　time　history　analysis　was　conducted　to　assess　seismic　responses.　In　addition,　incremental　dynamic　analysis　and　fragility　analysis　were　conducted　to　quantify　the　probability　of　damage.　The　results　indicated　that　the　enhanced-elongation　mechanism　reduced　the　failure　risk　of　SMA　dampers　and　increased　the　collapse　prevention　capacity　of　the　structures.　©　2024　Elsevier　Ltd