Welcome to CivFanatics!
First, verify your game cache: Steam --> Library --> Right-click Sid Meier's Civilization V--> Properties --> Local Files --> Verify Integrity of Game Cache.
If that doesn't help, please post your DxDiag file: Hit the "Windows key" and "R", type in Dxdiag, hit enter. A menu will appear, with a save option at the right bottom. Save the file and attach it here. This provides us with essential information about your system.
Thanks.