A　slab-column　joint　in　a　flat　plate　structure　may　exhibit　upward　or　downward　punching　shear　(UPS　and　DPS)　failure　when　subjected　to　different　abnormal　loading　conditions.　This　can　cause　distinct　residual　deformations　of　the　slabs,　which　in　turn　influences　the　behavior　of　the　consequent　progressive　collapse　of　the　entire　structure.　This　paper　presents　two　experimental　tests　on　two　2　x　2-bay,　1/3-scaled　flat　plate　substructure　specimens.　Both　tests　were　conducted　in　two　loading　phases.　In　the　first　loading　phase　(LP-1),　the　interior　column　of　specimens　UPS-Sub　and　DPS-Sub　was　subjected　to　a　gradually　increased　upward　and　downward　concentrated　load,　respectively,　until　punching　failure　occurred　at　the　interior　slab-column　joint.　In　the　second　loading　phase　(LP-2),　an　incremented　downward　uniformly　distributed　load　was　applied　on　the　slab　of　both　specimens　up　until　the　ultimate　state　just　before　a　complete　collapse　of　the　slab.　After　LP-1,　local　and　global　damage　patterns　were　observed　respectively　from　UPS-Sub　and　DPS-Sub.　The　punching　shear　strength　and　the　corresponding　displacement　of　the　interior　joint　in　UPS-Sub　were　found　to　be　58.2%　higher　and　53.6%　lower,　respectively,　than　the　corresponding　ones　in　DPS-Sub.　In　LP-2,　due　to　the　upward　residual　deformation　of　the　slab　in　UPS-Sub　as　a　result　of　LP-1,　its　first　peak　load,　vertical　displacement,　and　horizontal　displacement　under　compressive　membrane　action　were,　respectively,　8.4%,　91.1%,　and　57.1%　larger　than　those　in　DPS-Sub.　On　the　other　hand,　the　postpunching　peak　load　of　the　two　specimens　under　tensile　membrane　action　were　identical.　To　offer　an　in-depth　understanding　of　the　mechanical　behavior　that　resulted　from　upward　or　download　punching　shear　failure,　the　punching　shear　strengths　of　the　interior　slab-column　joints　and　collapse　resistance　of　the　substructures　were　also　analytically　investigated.　(C)　2021　American　Society　of　Civil　Engineers.