By RAW it doesn't work. Since you're creating beams to bar the door, you'd be affecting the door, not the people breaking it down. Thus it's the door that should be making the will save.
Unfortunately, objects always succeed on their save against shadow conjuration (as per the last line of the spell text), so the spell shouldn't have any effect on someone trying to break the door down.
Except for the fact that even if the save is made, the object is still 60% real. So it would seem then you have a metal bar that's 60% as strong as a real metal bar. The DC to bend an iron bar is 24, so in this case the DC to bend the shadow bar would be 14 then? Hmmm...