Shear-induced　rock　bridge　fractures　greatly　threaten　the　stability　of　rock　slopes　and　deep　rock　masses,　owing　to　their　connection　with　pre-existing　discontinuities.　In　this　research,　direct　shear　tests　on　sandstone　rock　bridges　were　performed　under　constant　normal　stiffness　(CNS)　conditions.　The　effects　of　rock　bridge　length,　initial　normal　stress　and　normal　stiffness　on　the　shear　behavior　of　rock　bridges　were　carefully　investigated,　encompassing　both　the　pre-failure　(cracking　phase)　and　post-failure　(sliding　phase)　stages.　Test　results　revealed　that　these　three　factors　variably　impact　the　shear　strength,　dilation　characteristics,　failure　pattern　and　acoustic　emission　response　of　the　rock　bridges.　In　particular,　normal　stiffness　was　found　to　greatly　affect　the　post-peak　slip　behavior.　It　was　observed　that　shear-induced　rock　bridge　fractures　exhibit　distinctive　shear　contraction　characteristics,　which　contrast　with　tension-induced　splitting　fractures　that　are　typically　marked　by　shear　dilation.　The　shear　contraction　mechanism　of　rock　bridge　fractures　was　elucidated　using　a　conceptual　cracking　model,　termed　the　TST　model.　This　research　contributes　fresh　insights　to　the　comprehension　of　dynamic　slip　hazards　prompted　by　the　rupture　of　rock　bridges　in　deep　rock　engineering.　©　The　Author(s)　2025.