Crédits : https://commons.wikimedia.org/wiki/File:Bending_steel_girders._Washington,_D.C.,_Sept._23._Officials_of_the_steel_industry_and_the_U.S._Bureau_of_Standards_inspect_one_of_the_large_riveted_steel_frame_knees_that_were_placed_thru_LCCN2016872383.jpg