Working Stress Method | Limit State Method |
This method is based on the elastic theory which assumes that concrete and steel are elastic and the stress strain curve is linear for both. | This method is based on the actual stress-strain curves of steel and concrete. For concrete, the stress strain curve is nonlinear. |
In this method the factor of safety are applied to the yield stresses to get permissible stresses. | In this method, Partial safety factors are applied to get design values of stresses. |
No factor of safety is used for loads. | Design loads are obtained by multiplying partial safety factors of load to the working loads. |
Exact margin of safety is not known. | Exact margin of safety is known. |
This method gives thicker, sections, so less economical. | This method is more economical as it gives thinner sections. |
This method assumes that the actual loads, permissible stresses and factors of safety are known. So it is called as deterministic method. | This method is based upon the probabilistic approach which depends upon the actual data or experience, hence it is called as non-deterministic method. |