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Load Combinations: ASCE 7-10 ASD

In the United States, ASCE 7-10 is an key part of the building code. It focuses on the requirements for general structural design, as well as providing a means for determining loads (dead, live, soil, flood, snow, rain, ice, earthquake, wind) and their combinations.

Allowable Strength Design (ASD) involves eight basic load combination equations.

This article will focus on how SkyCiv’s auto generated load combinations feature meets the load combination equations as specified in ASCE 7-10 ASD.

2.4.1 Basic Combinations

Design Code Equation	Design Code Comment	SkyCiv Equation	SkyCiv Comment
D	Eq. 2.4.1.1	G	-
D + L	Eq. 2.4.1.2	G + Q_L	-
D + (L_r or S or R)	Eq. 2.4.1.3	G + Q_S	The load type Q_S "Snow" is sub-categorized into "snow", "roof live", and "rain". Selecting this load combination will automatically create 3 load combination equations due to the use of "or" in the equation specification.
D + 0.75L + 0.75(L_r or S or R)	Eq. 2.4.1.4	G + 0.75Q_L + 0.75Q_S	The load type Q_S "Snow" is sub-categorized into "snow", "roof live", and "rain". Selecting this load combination will automatically create 3 load combination equations due to the use of "or" in the equation specification.
D + (0.6W or 0.7E)	Eq. 2.4.1.5	G + 0.6Q_W G + 0.7E	Due to the presence of an "or" in the load combination, two load combination eqations are required to represent them. Since "wind" and "seismic" are not linked by a load type, two separate equations are given by SkyCiv, instead of auto-generating equations in the case of the Q_S snow load type.
D + 0.75L + 0.75(0.6W) + 0.75(L_r or S or R)	Eq. 2.4.1.6a	G + 0.75Q_L + 0.45Q_W + 0.75Q_S	The load type Q_S "Snow" is sub-categorized into "snow", "roof live", and "rain". Selecting this load combination will automatically create 3 load combination equations due to the use of "or" in the equation specification.
D + 0.75L + 0.75(0.7E) + 0.75S	Eq. 2.4.1.6b	G + 0.75Q_L + 0.75Q_S + 0.525E	Only one load equation is required to represent this load combination. Despite the presence of Q_S "Snow" load type, only one equation is generated by SkyCiv for the "snow" sub-type.
0.6D + 0.6W	Eq. 2.4.1.7	0.6G + 0.6Q_W	-
0.6D + 0.7E	Eq. 2.4.1.8	0.6G + 0.7E	-

Design Code Equation

Design Code Comment

SkyCiv Equation

SkyCiv Comment

Eq. 2.4.1.1

D + L

Eq. 2.4.1.2

G + Q_L

D + (L_r or S or R)

Eq. 2.4.1.3

G + Q_S

The load type Q_S "Snow" is sub-categorized into "snow", "roof live", and "rain". Selecting this load combination will automatically create 3 load combination equations due to the use of "or" in the equation specification.

D + 0.75L + 0.75(L_r or S or R)

Eq. 2.4.1.4

G + 0.75Q_L + 0.75Q_S

D + (0.6W or 0.7E)

Eq. 2.4.1.5

G + 0.6Q_W
G + 0.7E

Due to the presence of an "or" in the load combination, two load combination eqations are required to represent them. Since "wind" and "seismic" are not linked by a load type, two separate equations are given by SkyCiv, instead of auto-generating equations in the case of the Q_S snow load type.

D + 0.75L + 0.75(0.6W) + 0.75(L_r or S or R)

Eq. 2.4.1.6a

G + 0.75Q_L + 0.45Q_W + 0.75Q_S

D + 0.75L + 0.75(0.7E) + 0.75S

Eq. 2.4.1.6b

G + 0.75Q_L + 0.75Q_S + 0.525E

Only one load equation is required to represent this load combination. Despite the presence of Q_S "Snow" load type, only one equation is generated by SkyCiv for the "snow" sub-type.

0.6D + 0.6W

Eq. 2.4.1.7

0.6G + 0.6Q_W

0.6D + 0.7E

Eq. 2.4.1.8

0.6G + 0.7E

Load Combinations: ASCE 7-10 ASD

2.4.1 Basic Combinations

Example: All Load Types Assigned