A structural beam subjected to sagging bending has a cross - section which is an unsymmetrical I - section. The overall depth of the beam is 300 mm. The flange stresses are
σtop = 200 N/mm2
σbottom = 50 N/mm2
What is the height in mm of the neutral axis above the bottom flange?
1
240 mm
2
60 mm
3
180 mm
4
120 mm