The　clamping　force　relaxation　of　bolted　joints　caused　by　contact　creep　at　ambient　temperature　has　a　significant　impact　on　the　service　performance　of　offshore　structures,　which　may　increase　their　vulnerability　to　additional　non-typical　loads.　Maxwell　and　Kelvin　architectures　are　introduced　to　analyze　the　creep　displacement　of　rough　surfaces　in　contact.　Subsequently,　a　theoretical　model　is　established　to　characterize　the　functional　relationship　between　contact　creep　and　clamping　force　relaxation.　The　model　parameters　are　obtained　from　a　compression　creep　experiment.　An　experimental　device　is　developed　to　validate　the　proposed　model.　The　experimental　results　show　a　good　agreement　with　theoretical　calculations.　In　addition,　the　influences　of　bolt　preload　and　surface　topography　on　the　clamping　force　relaxation　are　investigated　quantitatively,　and　find　that　the　clamping　force　relaxation　is　proportional　to　the　surface　roughness.　Thus,　controlling　surface　topography　and　bolt　preload　could　be　an　effective　way　to　improve　performance　of　bolted　joints　for　steel　structures.