(Statics/Math) I need to figure out how to calculate the reaction forces at the supports along two beams, but I've never seen supports in this manner. Pic below in a moment.

Question

mendicant_bias · Answer

I can't figure out how to treat that middle roller support. It's a roller, so there's no x-reaction force, but there's supposed to be a y-reaction force....but both of its sides has a beam along it?

mendicant_bias · Answer

I took the first section of the beam along the lefthand side from A to the roller support and treated that roller as normal, and calculated the reactions at A and C, where Ay = 60, and Cy = 60, both in kilonewtons. I'm not sure if that's right, though...and I have no idea how to from there, calculate the three separate reactions in the right-hand beam.

mendicant_bias · Answer

I'll just state what I think is true, and hopefully somebody can jump in and correct me if I'm wrong:

$$\sum_{}^{} M _{A} = 0$$(Roller joint, the sum of the torque about that point should always be zero)

$$B_{x} = 0$$(No forces acting in the x-direction; roller joint has no x-reaction force)

$$C_{x} = 0$$(Where C is the roller joint)

$$A_{x} = 50 $$ (The only action force on the lefthand beam acting in the x-direction is that of the vector coming in at an angle, and sigma Fx must sum to zero)

Does all this seem right so far?

amistre64 · Answer

there are x direction forces ... that 130Kn has a left and down component

amistre64 · Answer

im thinking the 12kN could be better modeled with a center of gravity ... 5m from B maybe?

mendicant_bias · Answer

(I wasn't mentioning every force or every thing I could calculate or thought of, but just the things that I feel pretty certain about that are nonetheless not immediately obvious); $$\sum_{}^{}M_{A} = 0$$ is definitely true. 

$$\sum_{}^{}M_{B} \neq 0$$ is also definitely true.

$$\sum_{}^{}M_{C} = 0$$ is true.

$$A_{X}, \ A_{Y} \neq 0$$ is also true.

$$C_{X} = 0, C_{Y} \neq 0 $$ is true.

Just that point C that I made up (and its equal and opposite reaction forces if the beam is split) is making me nervous about how to correctly model this. I feel like I'm going to make a significant mistake with sign conventions and assumptions of signs somewhere in here.