# Three Member Frame - Pin/Roller Central Bending Moment

on . Posted in Structural Engineering

## Three Member Frame - Pin/Roller Central Bending Moment formulas

 $$\large{ R_A = R_B = \frac{M_C}{L} }$$ $$\large{ H_A = 0 }$$ $$\large{ M_{max} \;(at \; C) = \frac{M_C}{2} }$$ $$\large{ \theta \;(at \; C) = \frac{M_C\;L}{12 \; \lambda \; I} }$$

### Where:

 Units English Metric $$\large{ h }$$ = height of frame $$\large{in}$$ $$\large{mm}$$ $$\large{ H }$$ = horizontal reaction load at bearing point $$\large{lbf}$$ $$\large{N}$$ $$\large{ I_h }$$ = horizontal member second moment of area (moment of inertia) $$\large{in^4}$$ $$\large{mm^4}$$ $$\large{ I_v }$$ = vertical member second moment of area (moment of inertia) $$\large{in^4}$$ $$\large{mm^4}$$ $$\large{ M }$$ = maximum bending moment $$\large{lbf-in}$$ $$\large{N-mm}$$ $$\large{ \lambda }$$  (Greek symbol lambda) = modulus of elasticity $$\large{\frac{lbf}{in^2}}$$ $$\large{PA}$$ $$\large{ A, B, C, D, E }$$ = point of intrest on frame - - $$\large{ \theta }$$ = slope of member $$\large{deg}$$ $$\large{rad}$$ $$\large{ L }$$ = span length under consideration $$\large{in}$$ $$\large{mm}$$ $$\large{ R }$$ = vertical reaction load at bearing point $$\large{lbf}$$ $$\large{N}$$

## diagrams

• Bending moment diagram (BMD)  -  Used to determine the bending moment at a given point of a structural element.  The diagram can help determine the type, size, and material of a member in a structure so that a given set of loads can be supported without structural failure.
• Free body diagram (FBD)  -  Used to visualize the applied forces, moments, and resulting reactions on a structure in a given condition.
• Shear force diagram (SFD)  -  Used to determine the shear force at a given point of a structural element.  The diagram can help determine the type, size, and material of a member in a structure so that a given set of loads can be supported without structural failure.
• Uniformly distributed load (UDL)  -  A load that is distributed evenly across the entire length of the support area.

Tags: Frame Support