will plastic design is really worth than elastic design of structures?

Question

they say plastic design is better. But i fear sometimes the sections are too slender and concept of plastic hinges does not hold good for material other than steel

Answer 1

I prefer concrete and steel

Answer 2

Plastic materials can contribute vibrational energy absorption (i.e., damping) and transient energy absorption (crash energy dissipation) that more elastic materials like steel or more brittle materials like concrete cannot. Some machine designs include static loading into the plastic range (like the single-use connecting-rod bearing bolts for my old Jetta). However I would think fatigue resistance is a must in structure designs in which dynamic loads routinely drive materials into the plastic deformation range (or are applied to normally plastic materials). Hinges, if one-piece, sound bad; I've lost count of the hinges used on small boxes, car radio pushbuttons and other applications that have fatigue-failed on me.