Engineering categories

From: Wikipedia:Categorization:
'There are often occasions when articles might ideally be moved from a category to two or more of its subcategories, but not all of the subcategories exist. In such cases consider creating the additional subcategories, but if you decide not to do so, leave the articles in the parent category for the time being.' 

I have replaced the categories on Arup. If you feel there are better subcategories to put them in, feel free to create them. In the meantime, the article should stay in the engineering categories as it places the article in the right place should someone be looking for structural, civil, mechanical engineers etc