Local　component　failure　may　change　force　transfer　path　of　a　steel　frame　structure.　In　addition　to　affecting　the　mechanical　performance　of　the　structure　directly　above,　the　lower　structure　may　also　be　affected　by　impact　of　local　block　falling.　The　lower　structure　can　resist　impact　load,　which　is　an　important　study　content　of　frame　structure　resisting　progressive　collapse.　The　dynamic　characteristics　of　the　lower　frame　beam　impact　is　very　important　to　the　study　of　its　anti-collapse　ability,　in　which　the　maximum　displacement　and　the　change　of　impact　force　are　the　key　dynamic　characteristics.　Here,　firstly,　considering　the　two　extreme　cases　of　complete　plastic　impact　and　complete　rigid　impact,　according　to　the　conservation　of　momentum　and　energy,　combined　with　the　deformation　energy　function　of　frame　beam,　the　upper　and　lower　limit　values　of　beam　maximum　displacement　after　block　impact　were　determined.　Then,　the　correctness　of　the　maximum　displacement　theoretical　analysis　was　verified　with　existing　falling　hammer　impact　tests.　The　results　showed　that　when　the　velocity　of　falling　block　is　smaller,　the　impact　is　close　to　complete　rigid　impact,　while　when　the　velocity　is　higher,　the　impact　is　close　to　complete　plastic　impact;　when　impact　point　of　falling　block　is　close　to　the　mid　span,　the　theoretical　model　is　close　to　the　finite　element　model;　when　impact　point　is　located　at　constraint　end,　the　complete　rigidity　theoretical　calculation　value　is　larger　than　the　simulation　value.　©　2021,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.