I'm discovering how much I like taking and looking at abstracts. This one really makes a point of contrasting the sharp curve with the clouds, as you mentioned. Great job!
The favorite is mostly sentimental for me, being a former Midwesterner who's stood in the top of that thing while it swayed in a thunderstorm, but it is also a very good photo. Congrats on a strong finish!
Great image here of the gateway to the west ;) The simplicity of the form is wonderful. The frame doesn't really add much to the composition though IMHO. (7)
Great job isolating the arch from distracting elements. The lighting really accentuates the shape - and has a great range of dark to light. The blue blue sky with interesting clouds makes a dramatic backdrop that compliments the subject and links to your title.
This is the best shot Ive seen of this structure. I think the light is hitting it at a good angle. Going from corner to corner of your frame is good. I think your frame improves this too.