I was talking to someone at work then all of a sudden I wondered why somethings are corrugated/ribbed/waffled (there are items like that around me at work). An engineer type at work told me it increases the objects structrural strength or some such. When asked to explain in more depth he was at a loss as this was a long time ago that he had studied the subject. I proceeded to waste work time to google this phenomenon, I HAD to know. I feel better now.