Figure 1. Trusses
Figure 1. shows a truss composed of poles. It is stored in fixed bearing A and fixed bearing B. At the nodes N, P and R, forces act as shown in the figure. All joints are torque and friction free.
- Explain with a sketch, and without calculation, what type of load bar AJ is exposed to (pressure or tension). Indicate any “zero bars” in the truss and show one of them why it is a zero bar. Show whether the truss is internally statically determined or internally statically indeterminate.
- Calculate the reaction forces (bearing forces) in fixed bearing A and fixed bearing B. Calculate the forces in the rods KM and IL (indicate pressure or tension). Can rod LN be replaced with a rope? Justify the answer.
Task 2
A person at a fitness center holds a weight with mass as shown in figure 2. The exercise machine is fixed clamp E and has a fixed bearing F. You can assume that bolt bearings (joints) A and C, pulleys B and D and fixed bearing F are friction-free. Components: Pulleys B and D, ACD, AE and CF.
- draw a free body diagram for each of the components of exercise equipment and look at the forces and moments that may act on each component (for the given load).
- Calculate the friction force (bearing forces and any clamping torque) in E and F For the exercise machine. Indicate the direction of the reactions.
