Covered hopper car

1. A car body for a covered hopper railroad freight car, the car body comprising: a pair of opposite sides and a pair of opposite ends defining a width, a height, and a length, the car body including a plurality of cargo hoppers between the opposite sides, and each of the opposite sides extending over a majority of a height of the car body and including a substantially flat, generally vertical upper side wall portion defining a plane, wherein each of the upper side wall portions includes at least one longitudinally extending stiffener member formed therein, each longitudinally extending stiffener member includes a channel that protrudes inwardly of the plane, wherein the car body further comprises a roof extending along a length of the car body and extending transversely from one to the other of the opposite sides, the roof being attached to a planar upper margin of each of the opposite upper side wall portions, the planar upper margin is bent inwardly to provide an inwardly and upwardly inclined flange portion, wherein each of the upper side wall portions includes a generally vertical part, the planar upper margin, and a planar inclined part disposed between the generally vertical part and the planar upper margin, the planar inclined part being bent inwardly relative to the generally vertical part, and the planar upper margin being bent inwardly relative to the planar inclined part.

2. The car body of claim 1 , wherein the width/thickness ratio of the inclined part does not exceed 60.

3. The car body of claim 2 , wherein the radius/thickness ratio of the roof does not exceed 750.

4. The car body of claim 1 , wherein the opposite sides include convexly curved lower side portions and each lower side portion includes a bottom chord protruding laterally outward and extending along a bottom margin of each lower side portion.

5. The car body of claim 1 , wherein the at least one longitudinally extending stiffener member of each upper side wall portion includes two longitudinally extending stiffener members each having a channel that protrudes inwardly of the plane.

6. The car body of claim 5 , wherein the two longitudinally extending stiffener members include first and second channels each having a curvilinear cross-sectional shape.

7. The car body of claim 6 , wherein the radius/thickness ratio of each of the first and second channels does not exceed 500.

8. The car body of claim 5 , wherein the two longitudinally extending stiffener members include first and second channels each having a rectilinear cross-sectional shape.

9. The car body of claim 8 , wherein the rectilinear cross-sectional shape is a cross-sectional shape of a trapezoid.

10. The car body of claim 8 , wherein the width/thickness ratio of each of the first and second channels does not exceed 70.

11. The car body of claim 1 , wherein the at least one longitudinally extending stiffener member includes at least one channel having a curvilinear cross-sectional shape.

12. The car body of claim 11 , wherein the radius/thickness ratio of the at least one channel does not exceed 500.

13. The car body of claim 1 , wherein the at least one longitudinally extending stiffener member includes at least one channel having a rectilinear cross-sectional shape.

14. The car body of claim 13 , wherein the rectilinear cross-sectional shape is a cross-sectional shape of a trapezoid.

15. The car body of claim 13 , wherein the width/thickness ratio of the at least one channel does not exceed 70.

16. The car body of claim 1 , wherein each of the opposite sides includes a lower side portion that includes at least one longitudinally extending stiffener portion formed therein.

17. The car body of claim 1 , wherein the roof and the upper margin are free from one or more reinforcing structures at junctions formed by the roof and the planar upper margins.

18. The car body of claim 1 , wherein each of the upper side wall portions includes only one of the longitudinally extending stiffener member formed therein.