Comparison of Working Stress Method and Limit State Method

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.


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