The　purpose　of　this　study　is　to　investigate　the　dynamic　behavior　of　steel　deck-arch　bridges　with　side-by-side　multiple　vehicle　loadings　moving　over　a　rough　deck.　A　brief　description　of　analytical　theory　is　provided,　including　vehicle　model,　bridge　model,　and　numerical　methods.　Both　vehicle　and　bridge　are　treated　as　three-dimensional　models.　The　effectiveness　of　mode　superposition　and　Newmark　numerical　methods　are　investigated.　Most　of　the　important　factors　that　affect　the　dynamic　response　of　bridges　are　considered　in　this　study.　The　effects　of　the　deck,　column　and　arch　boundary　conditions　are　also　studied,　and　the　analytical　impact　factors　of　deck,　column,　and　arch　rib　are　compared　with　those　determined　on　the　basis　of　current　American　Association　of　State　Highway　and　Transportation　Officials　(AASHTO)　specifications.　Study　results　are　useful　for　both　bridge　engineers　and　bridge　engineering　researchers.　DOI:　10.1061/(ASCE)BE.1943-5592.0000243.　(C)　2012　American　Society　of　Civil　Engineers.