Merry Xmas

Cutting corners to save money, so common in the PRC. Why use 8 when 4 will do, and the construction boss and school leaders/party bigwigs can pocket the leftover cash for expensive meals, ktv whores, gambling junkets to macau, designer shopping for the er nai in HK etc etc...

I'm not an engineer, but do know something about reinforced concrete, having worked with RCP's before, the stress above a pipe or in the case of a building that is load bearing, has to be properly calculated as you rightly say, so what they were doing was cutting corners deliberately, at the risk of peoples lives with the tragic results it inevitably entailed.