Civil Engineering Reference
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Table 2-7(a) ACI Load Combinations for Building Subjected for Dead, Live Wind, and Earthquake Loads
(W is based on service-level wind loads)
ACI
Equations
Garages, places of public assembly
and all areas where L is greater than
100 lb/ft
2
Other buildings
Eq. (9-1)
U = 1.4D
U = 1.4D
Eq. (9-2)
U = 1.2D + 1.6L + 0.5L
r
U = 1.2D + 1.6L + 0.5L
r
Eq. (9-3)
U = 1.2D + 1.6L
r
+ 1.0L
U = 1.2D + 1.6L
r
+
0.8W
U = 1.2D + 1.6L
r
+ 0.5L
U = 1.2D + 1.6L
r
+
0.8W
Eq. (9-4) U = 1.2D
+
1.6W + 1.0L + 0.5L
r
U = 1.2D
+
1.6W + 0.5L + 0.5L
r
Eq. (9-5) U = 1.2D
+
1.0E + 1.0L
U = 1.2D
+
1.0E + 0.5L
Eq. (9-6)
U = 0.9D
+
1.6W
U = 0.9D
+
1.6W
Eq. (9-7)
U = 0.9D
+
1.0E
U = 0.9D
+
1.0E
Table 2-7(b) ACI Load Combinations for Building Subjected for Dead, Live Wind, and Earthquake Loads
(W is based on strength-level wind loads)
ACI
Equations
Garages, places of public assembly
and all areas where L is greater than
100 lb/ft
2
Other buildings
Eq. (9-1)
U = 1.4D
U = 1.4D
Eq. (9-2)
U = 1.2D + 1.6L + 0.5L
r
U = 1.2D + 1.6L + 0.5L
r
Eq. (9-3)
U = 1.2D + 1.6L
r
+ 1.0L
U = 1.2D + 1.6L
r
+
0.5W
U = 1.2D + 1.6L
r
+ 0.5L
U = 1.2D + 1.6L
r
+
0.5W
Eq. (9-4)
U = 1.2D
+
1.0W + 1.0L + 0.5L
r
U = 1.2D
+
1.0W + 0.5L + 0.5L
r
Eq. (9-5)
U = 1.2D
+
1.0E + 1.0L
U = 1.2D
+
1.0E + 0.5L
Eq. (9-6)
U = 0.9D
+
1.0W
U = 0.9D
+
1.0W
Eq. (9-7)
U = 0.9D
+
1.0E
U = 0.9D
+
1.0E
D = dead loads, or related internal moments and forces
L = live loads, or related internal moments and forces
L
r
= roof live load, or related internal moments and forces
U = required strength to resist factored loads or related internal moments and forces
W = wind load, or related internal moments and forces
E = earthquake loads, or related internal moments and forces
The ACI Code permits the load factor applied to the live load L to be reduced to 0.5 in Eq. (9-3) to (9-5)
(ACI 9.2.1). This reduction cannot be applied for garages, areas occupied as places of public assembly, and all
areas where L is greater than 100 lb/ft
2
. It is important to point out that this reduction in the load factor can be
applied in addition to the live load reduction described in Section 2.2.3.
For design of beams and slabs, the factored load combinations used most often are:
U = 1.4D
ACI Eq. (9-1)
U = 1.2D + 1.6L
ACI Eq. (9-2)
ACI Eq. (9-1) seldom controls—only when the live load to dead load ratio (L/D) is less than 0.125.
For a frame analysis with live load applied only to a portion of the structure, i.e., alternate spans (ACI 8.11),
the factored loads to be applied would be computed separately using the appropriate load factor for each load.
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