Can I rip down joists?

[GlassBlockMan]

I'm planning how to fit a large shower tray and glass block wall into a first floor bathroom with suspended floor. I want to know if i can rip the top of some floor joists down to accomodate the shower tray so that it is flush with the floor and still have enough strength in the joists to take the glass block wall.

The joists are recently fitted and 47x147mm@ 400mm centres.
The span of the joists is 1.8m from wall to wall.
The glass block wall will be perpendicular to the joists, approx 1/3 of the span from the edge and will weight approx 150kg per meter of glass block wall
I would like to rip about 35mm off the top of the joists between the glass block wall and further edge - 2/3 of the span.

Anyone got any idea if I can do this or am I mad thinking about it?

 

[big-all]

in general the maximum is 1/8th depth away from the end or middle
you can possibly go more if the joist is on a short span but you need calculations
you are going for 1/5th so no with out calculations

 

[Static]

Basic answer is no the joists would deflect too much and are close to failing..
Better off sistering the joists with 100mm deep members bolting them together over the shower area..