In 1943, graduate student Paul Newman Gillett submitted a thesis to the Department of Civil Engineering at Michigan State College of Agriculture and Applied Science in the USA.
Entitled “The Design of Bomb Shelters”, it draws on technical information about European shelters to provide a fascinating read.
You can download the file from the Michigan State University website here: https://d.lib.msu.edu/etd/9892/datastream/OBJ/download/The_design_of_bomb_shelters.pdf