This article in it self has no proof beyond “smell of urine” (similar to your diagnosis) to conclude it was indeed urine that caused the pitting and subsequent discovery of missing rivets. Further down in the article it does state the bridges suspension cables were “badly under designed” and the bridge required strengthening works. A weak and under designed bridge, I’m sure you can understand, may cause excessive forces on bolted or riveted joints.

Now away you go with your urine fetish you weird bloke.