Long-span　concrete　filled　steel　tube　(CFST)　arch　bridges　often　suffer　from　serious　vehicle-induced　dynamic　responses　during　service,　but　the　reasons　and　effects　of　certain　remarkable　vehicle-induced　dynamic　responses　are　not　yet　deeply　explored.　Taking　a　typical　long-span　CFST　arch　bridge　as　a　research　object,　its　typical　diseases　were　investigated.　Based　on　the　field　testing　and　theoretical　analysis,　the　typical　diseases　and　the　effects　of　supports　void　were　studied.　The　field　investigation　and　test　results　show　that　the　void　of　main　girder　supports　causes　differential　settlement　on　both　sides　of　the　expansion　joint,　and　aggravates　the　vehicle　impact　on　the　main　girder　and　suspenders.　The　impact　factors　of　displacement　near　the　expansion　joint　and　midspan　reach　1.52　and　1.15　respectively.　The　variation　rate　of　stress　amplitude　in　suspenders　is　between　-28.0%　and　18.5%.The　numerical　results　show　that　the　vehicle-induced　dynamic　responses　of　the　steel　box　girder　and　suspenders　change　significantly　before　and　after　supports　get　void.　The　void　of　the　supports　causes　obvious　along-bridge　displacement　of　the　main　girder,　which　may　reach　the　same　magnitude　as　the　vertical　displacement.　The　peak　value　of　vehicle-induced　acceleration　of　the　steel　box　girder　increases　significantly　after　supports　get　void,　and　the　impact　will　be　more　significant　when　the　supports　and　steel　box　girder　are　still　able　to　collide　with　each　other　under　vehicle　load.　The　stress　amplitude　in　suspenders　changes　remarkably　after　the　supports　get　void,　and　its　effect　on　short　suspenders　is　more　obvious.　The　void　of　supports　is　one　of　the　main　reasons　for　the　significant　change　of　vehicle-induced　impact　responses　of　the　steel　box　girder,　suspenders　and　other　components　of　this　type　of　bridge.　©　2020,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.