Describe Limit state design?

1. The yielding of a critical fibre of cross-section is a measure to estimate the capacity of a structure in elastic condition. 

2. The section naturally resists more design action such as bending/axial force / shear.

3. Uncertainties in estimation of load, imperfection in materials,  imperfection in geometry members,  effect of residual stress, etc..,are considered in one factors therefore the factor of safety in WSM.