How can i measure react force of ground, caused by gravity force?

Hello!

I have the SimMechanics model of cube (mass of the cube - 100kg), which connected with ground trough two pillars (So i have four Body blocks - cube, two pillars and ground). I want to measure reaction on gravity force, that acts from the ground to this to pillars, separately. All joints are Weld. When I add joint sensors to the Weld joins, between ground and pillars, set it to measure reaction force and scope the results, I see next picture: one scope shows me full reaction (of all construction) from ground, and second scope shows me zero react. So, how can I measure distribution of the reaction forces on two pillars?

Thank You!