Best way to make an apron/sliding door interface?

My barn has a 2x2 angle iron in the floor. the top is flat with the floor and the vertical is on the outside edge going down to my apron. there is just a piece of vertical rebar on both outside door edges. when you close the door the bottom edge sits up againgts the angle iron and the vertical rebar keeps it from flying out away from the walls. once its closed I have to latch the inside edge latches to keep the door tight against the walls. that 2X2 edge on the floor strangthengs the edge I push snow out with a 1 ton plow truck and heavy blade and i havent hurt it yet it was put in in 1957. the 2' drop to the apron is negosiable buy just about everything. 

1 1/2" angle iron - welded rebar onto back side so it is into concrete it cane in handy also when screeting concrete as height was set along the 18' door length .
Friend who had overhead door used 2" pipe set into concrete so door seals against pipe