So far as I can recall, the Flash does not have super-strength. He wears a special suit that protects his body from the effects of travelling at super-speed. As far as strength is concerned, his one great advantage is the fact that the faster an object is moving, the greater the force of impact when it makes a sudden stop. (Because there is more energy built up in the momentum of his movement, and that energy must be transferred when he comes to a stop). So, if the flash is punching you at super-speed, it has the effect of super-strength, because his arm has built up more momentum than, say, Batman's would, and therefore, has the effect of hitting a motionless object with more impact force.
All that said, if he was to make high-velocity impact with something of a greater mass than him, chances are, he would crumple like origami... so we have to suspend our disbelief a little, or assume that the special suit protects him.
Flash has been seen (e.g. Flash vol 2 #101 May 1995) single-handedly reconstructing ruined buildings and moving heavy beams and girders into place. So, when he wants to, he CAN simulate super-strength effects by manipulating the inertia of objects that he's handling. For most practical purposes (villain-punching, infrastructure repair, etc), he honestly might as well have super-strength.
I believe that the Flash (all Flashes) does have superhuman strength, but not at the kind of levels characters like Cyborg and Aquaman would be at. Now I'm gonna assume you're talking about Barry. Now, Allen I believe is probably physically stronger than Batman, so I think he is probably able to bench press between 1,500 lbs and 3,000 lbs.