Complex sentence: Class 311000 trains were delivered between 1996 and 2006, and again from 2012 to now to expand service on the Gyeongbu Line and the Gyeongwon Line, and to replace older trains (1st and 2nd batch Class 1000 trains).
Split into simpler sentences: Class 311000 trains entered service between 1996 and 2006, and again from 2012 to now. They were introduced in 1996 to expand service on the Gyeongbu Line, the Gyeongin Line, and for replacing older trains (1st and 2nd batch Class 1000 trains).