ASD - Allowable Stress Design LFD - Load Factor Design LRFD - Load and Resistance Factor Design ASD: Allowable Stress Design ASD do...

## ASD - Allowable Stress DesignLFD - Load Factor DesignLRFD - Load and Resistance Factor Design

### ASD: Allowable Stress Design

ASD does not recognize different variabilities of different load types.

In LFD, load and resistance are not considered simultaneously.

### LRFD: Load & Resistance Factor Design

The LRFD philosophy provides a more uniform, systematic, and rational approach to the selection of load factors and resistance factors than LFD.

### Variability of Loads and Resistances:

Suppose that we measure the weight of 100 students…

Now suppose that we measure the strength of 100 ropes…

Reliability Index:

AISC:

Resistance Factor:

AISC Steel Construction Manual, 13th Edition

1. Dimensions and Properties
2. General Design Considerations
3. Design of Flexural Members
4. Design of Compression Members
5. Design of Tension Members
7. Design Consideration for Bolts
8. Design Considerations for Welds
9. Design of Connecting Elements
10. Design of Simple Shear Connections
11. Design of Flexible Moment Connections
12. Design of Fully Restrained Moment Connections
13. Design of Bracing Connections and Truss Connections
14. Design of Bearing Plates, Base Plates, and Column Splices
15. Design of Hanger Connections, Brackets Plates, etc.
16. Specifications and Codes
17. Miscellaneous Data and Mathematical Information Index

### LRFD

1. 1.4D
2. 1.2D + 1.6L + 0.5(Lr or S or R)
3. 1.2D + 1.6(Lr or S or R) + (0.5L or 0.8W)
4. 1.2D + 1.6W + 0.5L + 0.5(Lr or S or R)
5. 1.2D ± 1.0E + 0.5L + 0.2S
6. 0.9D ± (1.6W or 1.0E)

### ASD (Consistent with ASCE 7)

1. D
2. D + L
3. D + (Lr or S or R)
4. D + 0.75L + 0.75(Lr or S or R)
5. D ± (W or E)
6. D ± 0.75(W or E) + 0.75L + 0.75(Lr or S or R)
7. 0.6D ± (W or 0.7E)

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Strukts: AISC Steel Design Philosophies of Design
AISC Steel Design Philosophies of Design