1- Render your red bar (only the red bar itself) as a PNG image. To do that, go in Edit > Save Frame as and in the Output Modules, make it a PNG. (Or simply precomp it.)
2- Import your red bar PNG in your comp.
3- Apply Simulation > Shatter. In shapes, make it “Glass”. For further explanations about Shatter, go in your AE Effects Help Guide.
Background transparent = Alpha background.
In After Effects, Alpha background = black (or the gray and white grid, depends on your settings).
To render with an alpha, Make Movie > Output Modules > Quicktime Movie > RBG + Alpha.
Hope that helped.
Justin Productions
Tangerin01@hotmail.com
Adobe After Effects 6.0 Professional