drilled perforation

(A substantial increase in the service life of the supports and timber crossbeams may be achieved by mechanical pre-treatment (e.g. drilled perforation) or additionally applied two-layer protection (Ger.: Doppelstock-schutz) in the transition region between the air and the ground as is common practice with telephone masts)

rust allowance of ... mm.

crytical stray current load

through settlement

(The snow conditions of load case 2 are derived from load case 1 through settlement of the snow cover and a supplement for additional snowfall. The resulting increased average density is ри = 0.400 t/m3. This value applies to a basic altitude of 1500 m a.s.l. and an exposure of WNW-N-ENE.)

Заранее спасибо!

crytical stray current load - без контекста: критическая (разрушающая, вызывающая коррозию - см. по контексту) сила блуждающего тока

through settlement - с учётом оседания...