The book discusses some topics of modern structural mechanics, which, as experience shows, are not sufficiently studied at the universities. It has been written to provide an in-depth presentation of the fundamentals of the methods used in the design software, with a focus on analyzing basic assumptions and explaining the physical meaning of computational operations. This book is not intended for students who have just begun to study structural mechanics; it is aimed at structural engineers who want to further enhance their theoretical training. It can also be recommended to graduate and post-graduate students of construction universities.