Engineering Statics

E-4


A uniform slab of concrete weighing 40 kN is supported by three vertical cables AD, BE and CF. Determine the tensions in the cables.

The FBD of the slab is drawn with the weight vector 
in the negative y-direction and located at the center of 
the slab.
The summation of forces in the y-direction can be seen 
immediate from the FBD.
The moment equation is taken about the x-axis.  Note:  THIS 
IS A MOMENT ABOUT A LINE AND IS A SCALAR.
The moment equation is taken about the z-axis.
Three equation and three unknowns result.  They are 
rewritten with all unknowns arranged vertically and 
constants on the right side.  This is for convenience for 
entry into the calculator.