ASCE 7-22

ASCE 7-22 Section 2.3 | LRFD Load Combinations

Buildings must be designed to withstand simultaneous, probable extreme loads. Because a record earthquake is unlikely to hit exactly during a 500-year snowstorm, load combinations scale down loads when they act together.

Governing Formula

U = 1.2D + 1.0W + L + 0.5(L_r \text{ or } S \text{ or } R)

Variables

U

Required strength (Ultimate Load)

Force or Pressure

D

Dead load

Force or Pressure

W

Wind load

Force or Pressure

L

Live load

Force or Pressure

S

Snow load

Force or Pressure

Quick Example

Identify load components

Identify the Dead, Dead, Wind, and Snow components at a given node.

Test gravity combinations

Test equation 1.2D + 1.6L + 0.5S and 1.2D + 1.0L + 1.6S.

Test lateral combinations

Test lateral equations including uplift combinations like 0.9D + 1.0W to ensure the footing does not pull out of the ground.

When does this govern?

Different combinations govern different elements. 1.2D + 1.6L + 0.5S governs typical floors, while 0.9D + 1.0W governs anchorage against uplift.

Common Mistake

Forgetting to apply the 0.9 Dead Load combination to check for uplift and overturning of sheer walls or light roofs.

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Governing Formula

U = 1.2D + 1.0W + L + 0.5(L_r \text{ or } S \text{ or } R)

Variables

U

Required strength (Ultimate Load)

Force or Pressure

D

Dead load

Force or Pressure

W

Wind load

Force or Pressure

L

Live load

Force or Pressure

S

Snow load

Force or Pressure

Quick Example

Identify load components

Identify the Dead, Dead, Wind, and Snow components at a given node.

Test gravity combinations

Test equation 1.2D + 1.6L + 0.5S and 1.2D + 1.0L + 1.6S.

Test lateral combinations

Test lateral equations including uplift combinations like 0.9D + 1.0W to ensure the footing does not pull out of the ground.