Bridge building

The eighteenth entry is il carico permanente, and two places above it stands il carico da traffico. Italian names the pair for what they do: one is permanent, the other arrives with the traffic, and the codes call that second family il carico variabile. English has named the same pair since the first iron bridges, and named it by a metaphor now so worn that engineers no longer hear it: weight of the structure itself is the « dead load », and everything that walks, drives or blows across it is the « live load ». The two are not optional. « Permanent load » is understood and sounds like a translation; every drawing, every standard and every conversation on site says « dead » and « live ». The habit runs right through technical English: a cable carrying current is « live », a rail that has been switched off is « dead », and a « dead weight » is a load that does nothing but press down. So a bridge is described in one language as half alive, and in the other merely as half changeable.