Advantages of uding LRFD method and Comparison of ASD and LRFD
- LRFD is another tool for design of steel buildings. It provides flexibility to the designer in selecting design methodology.
- When dead load is larger as compared to live load then LRFD becomes economical.
- The behavior at the collapse including ductility, warning before failure are considered in LRFD. This is not directly possible in ASD method because here the structure is considered at service stage.
- Plastic design concepts may be employed in LRFD method but cannot be applied in ASD method.
- Every type of load may be given different factor of safety depending upon its probability of overload, number of occurences and changes in point of application. But in ASD same factor of safety is used for different loads.
- Safer structures may result under LRFD method because of considering behavior at collapse. But behavior at collapse is not considered in ASD method.
Disadvantages of Using LRFD method
- elastic behavior considered for load analysis and ultimate plastic behavior for material strengths are not compatible. However, percentage difference is less.
- Engineers experienced in ASD have to become familiar with this technique.
- Old books are according to ASD method and become ineffective.
- Validity of previous designs is still to be checked according to ASD.
Reference : Steel structures by Zahid Ahmad siddiqi and Muhammad ashraf