# LRFD Load Combinations

Choose the combination that results in the highest U, use U in your calculations.

D = Dead Load, L = Live Load, T = self-straining, H = earth pressure, = roof live load, S = Snow Load, R = rain load, E = earthquake load

In some sample problems I have seen and Q varibales. Individual load factors like 1.2 and 1.4 are sometimes represented as and the loads themselves are represented as . The factoring for a single load would then be , and all of them .

## Strength Reduction Factor ()

Strength reduction factors are applied to the nominal (design) strength:

or (this is seen pretty often in practice)

Where is determined with U from the factored loads. Strength reduction factors vary for concrete and steel.

### Concrete

0.9 for Tension controlled

0.7 compression with spiral steel

0.65 compression with tied steel

0.75 shear and torsion

0.65 bearing on concrete

Furthermore there is a range based on stress () value for beams () and the same equation applies to tied transition members. Spiral transition members use .

### Steel

0.9 for yield and 0.75 fracture

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