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Load Factors and Combinations per ACI 318-19 with ideCAD

How does ideCAD define load combinations according to ACI 318-19?

  • Load combinations are automatically generated.


D = dead load
E = earthquake load
Eh = effect of horizontal seismic forces
Em = seismic load effect, including overstrength
Emh = effect of horizontal seismic forces, including overstrength
Ev = vertical seismic effect applied in the vertically downward direction
L = live load
Lr = roof live load
R = rain load
S = snow load
U = strength of a member or cross section required to resist factored loads or related internal moments and forces in such combinations as stipulated in ACI 318-19
W = wind load

The required strength of a member U is controlled to at least equal to the effects of factored loads in ACI Table 5.3.1. Internal forces and moments resulting from the load combination are expressed as the required strength for the design.

Equations [ 1.2D+1.0E+1.0L+0.2S ] and [ 0.9D + 1.0E ] in ACI Table 5.3.1 are load combinations, including the seismic load effects, and the others are Basic Combinations. As specified in ASCE 7-16 Section 12, when the seismic load effect is combined with the effects of other loads, such as D and L, the seismic load combinations shown below are used.

As specified in ASCE 7-16 Section 12, where the seismic load effect with overstrength is combined with the effects of other loads, the following seismic load combination for earthquake-resistant structures is used.

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