I think I can see the symmetry you were attempting to capture in this photo. I think the primary problem is that this photo lacks pizzaz in the area of subjectivity. There is nothing in this photo that really grabs the viewer and holds their interest for any length of time. When planning your photos, you may want to try to keep that in mind. Voters are looking for high impact subjects as well as excellent technique...
I'm sure others will say the same, but... I find the angle annoying. I think you should have rotated the image so that the vents, and other framework, were horizontal. Besides that I like what you did with the colouring of this image.