Moment capacity concrete hollow beam 1

[LR11]

Has anyone come across a method to determine the capacity of a concrete hollow beam.
With a rectangular beam, the concrete stress block is quantified as (0.85.f'c)(γ.ku.d).
I can understand the "0.85.f'c" part but what would "γ" be?

The beam is rectangular and the void is rectangular.

 

[Settingsun]

Gamma is the same as usual. The trick is that the width changes if the compression zone extends below the top flange, into the webs.

Look up T-beam examples (or flanged I-beams) online or in a text book. It's the same principle. The total width of your two webs is substituted for the stem width of the T-beam.

 

[LR11]

OK thanks I'll give this a try.