D1.F.4.6.1 Cracked Moment of Inertia - ACI Beam Design
When beam design is done per ACI 318, STAAD will report the moment of inertia of the cracked section at the location where the design is performed. The cracked section properties are calculated in accordance with the equations shown below.
Rectangular Sections
Gross section (A) and cracked transform section (B) for rectangular shapes
Without compression steel
n = Es/Ec
Tee Shaped Sections
Gross and cracked transform sections for tee shapes without compression steel
Without compression steel
See D1.F.4.5 Beam Design Output for an example of output including the calculated cracked moment of inertia.