How to improve your photo
I think your subject is okay, but in order to present it in the manner that I think you wanted to convey to the viewer,(dizzying, breathtaking height), a different viewpoint and possibly focal length would have helped in this regard. I think that moving more directly under the tower and using a wide angle lens(I don't know which focal length you were using here) would have created that feeling of height you were looking for.
The sky as you probably know is pretty blown out because the sun was shining directly into your lens. When shooting silhouettes try to get your camera in the shade, use a lens hood, have the sun outside the frame, or hide the sun behind a part of the structure you are shooting to minimize its brightness. I would have moved my body to put the sun behind the widest part of the girders or scaffolding. Also you can create interesting lens flare or starburst effects by allowing only a tiny bit of the sun to peek around the girder or frame that you hide it behind.
A silhouette such as this tends to render the image more abstract in its presentation so in this case I would consider filling the frame more with the subject, eliminating the foreground and making the image a more graphic form study using the lines and angles within the structure as the 'subject' rather than the subject itself. The trees in the foregroud distract from that rather iconic graphic look that would work better here.