Difference between limit state and working stress method site:nptel.ac.in
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Working Stress Method(WSM)
Limit State Method(LSM)1.Follow Hooks law i.e. stress-strain diagram is linear.Does not follow Hooks law, hence stress strain diagram is non linear.2.All tensile stresses are taken by steel only and not by concrete.The tensile strength of concrete is ignored.3.Factor of safety is used.Here partial safety factors are used.4.It is based on deterministic approach i.e. original behavior of structure under real applied loads.It is based on probabilistic approach to design.5.Here material strength is under estimated and loads are working loads.Here material strength is under estimated and loads are generally working loads with extra safety i.e. overestimated. 6. WSM satisfies serviceability criteria but highly uneconomical.Major concern is Safety and Serviceability before failure.
Limit State Method(LSM)1.Follow Hooks law i.e. stress-strain diagram is linear.Does not follow Hooks law, hence stress strain diagram is non linear.2.All tensile stresses are taken by steel only and not by concrete.The tensile strength of concrete is ignored.3.Factor of safety is used.Here partial safety factors are used.4.It is based on deterministic approach i.e. original behavior of structure under real applied loads.It is based on probabilistic approach to design.5.Here material strength is under estimated and loads are working loads.Here material strength is under estimated and loads are generally working loads with extra safety i.e. overestimated. 6. WSM satisfies serviceability criteria but highly uneconomical.Major concern is Safety and Serviceability before failure.
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