Use the 'Search' facility on this site. Choose keywords like 'stress', 'design' etc. There have been plenty of posts similar to yours, which Mr. Breen, Mr. Luf and others have answered in great detail.
Here is my contribution. R. O. T (Rule Of Thumb) For Piping #1 - There is a Rule for everything #2 - For every rule there will be an exception #3 - The Boss is still the Boss #4 - Remember Rule #1