LRFD accounts for both variability in load and resistence. It achieves uniform levels of safety for different limit states.
Comparison of ASD & LRFD
Advantages of LRFD
ASD is the simple technique & LRFD is the sophisticated.
ASD combines dead and live lots and treats them in the same way.
In lrfd different load factors are assigned to dead lots and live lots, which is appealing.
Changes is load factors and resistence factors are much simpler to make in lrfd.
Mechanical properties of structural steel
Material
Length
X-section
Resistence to deformation based on:
Design technique
Preliminary member sizing of beams
Structural analysis - modeling, analysis
Design review - member modifications
Cost of estimation
Preparation of structural drawings and specifications
Lots for structural analysis and design
Dead load
Live load
Mean return period OR
Recurrence interval OR
Live lots for various occupencies
Reduction in basic design live load
Impact Load
Wind load
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