# Structural Analysis Problem- internal hinge

1. Sep 19, 2011

### ride5150

1. The problem statement, all variables and given/known data

3. The attempt at a solution

for part 1:

i figured that this structure is not in static equilibrium. once load "P" is applied, the roller at "D" will function as a fulcrum and ABC will lift (make an angle with the horizontal).

is that assumption correct?

based on what i assumed:

i assumed:

2 reactions at "A", -Ax and -Ay
0 reactions at B
1 reaction at "D", Dy

i summed the moments about "D"

(clockwise moment is negative)

(-PL)+(Ay4L)=0

Ay= -P/3L ========================

Sum of forces in Y direction = 0:

Ay+Dy-P= 0

Dy= P-Ay

after substituting for Ay:

Dy=(3PL+P)/(3L) =========================

i dont know how to find Ax.

is what i did so far correct?

2. Sep 20, 2011

### nvn

ride5150: That is currently incorrect. There is one reaction force at B, which is By. A roller symbol means a structure is constrained in the direction perpendicular to the roller, regardless whether the roller is in compression or tension. Hint 1: The moment at a frictionless hinge (point C) is always zero.