Flat　plate-column　joints　with　in-plane　constraints　exhibit　a　suspension　mechanism　under　large　deformations　after　punching　shear　failure,　which　significantly　affects　the　progressive　collapse　behavior　of　the　entire　flat　plate　structural　systems.　However,　in-plane　constraints　were　ignored　in　the　existing　tests　by　which　the　suspension　mechanism　could　not　be　exhibited　and　consequently　the　post-punching　resistance　was　significantly　underestimated.　To　fill　this　gap,　a　static　pushdown　test　was　conducted　on　eight　flat　plate-column　joints　with　in-plane　constraints　until　their　post　punching　resistances　being　completely　lost.　The　influences　of　the　punching　directions　and　the　structural　parameters　including　slab　thickness,　reinforcement　amounts　and　arrangement　of　flexural　reinforcement　on　the　post-punching　failure　mechanism　were　analyzed.　An　analytical　method　for　calculating　the　post-punching　strength　was　proposed　and　validated　by　the　test　results.　The　contributions　of　each　layer　of　reinforcement　to　the　post-punching　resistance　were　also　quantified.