if the opener rail is bending when the door closes at the bottom, the down limit on the opener is set to travel too far. Back it off some until the door stops just short of the concrete. Then increase the down travel just a little at a time until the door touches and starts to compress the rubber seal on the bottom. The opener rail should just tense up a little bit. What kind of opener did you install? Also, what kind of door is it attached too? You should be able to run the door up and down by hand without much effort. If you really have to push one way or lift very hard, door needs to be tuned up. Springs adjusted, rollers should spin freely, etc.