Structural Analysis Multiple Choice Questions on “Method of Joints”.
1. How many equilibrium equations do we need to solve generally on each joint of a truss?
a) 1
b) 2
c) 3
d) 4
Answer: b
Clarification: Summation of forces in x and y direction should be equated to 0. Since there is no bending moments in trusses, we don’t need to solve the third equation.
2. If a member of a truss is in compression, then what will be the direction of force that it will apply to the joints?
a) Outward
b) Inward
c) Depends on case
d) No force will be there
Answer: a
Clarification: Member will apply outward force. Joint will in turn apply inward force resulting in compression of the member.
3. If a member of a truss is in tension, then what will be the direction of force that it will apply to the joints?
a) Outward
b) Inward
c) Depends on case
d) No force will be there
Answer: b
Clarification: Member will apply inward force. Joint will in turn apply outward force resulting in compression of the member.
4. What should be ideally the first step to approach to a problem using method of joints?
a) Draw fbd of each joint
b) Draw fbd of overall truss
c) Identify zero force members
d) Determine external reaction forces
Answer: c
Clarification: Identifying zero force members should always be the first step to approach any truss problem as it eliminate a lot of variables and is fairly easy.
5. What should be the angle (in degrees) in the given system (part of a bigger system) if both of the members have to be a zero force member?
a) 22.5
b) 45
c) 67.5
d) 90
Answer: d
Clarification: 90o would mean that without any external force, each one would carry no force to satisfy equations of equilibrium.
In the above figure, force is applied at joint c and its magnitude is 10N with downward direction. This question is used for Q6-Q9.
6. Which of the following are 0 force members?
a) FG, HI, HJ
b) HI, HJ, AE
c) HI, HJ, HE
d) HI, HJ, FH
Answer: a
Clarification: FH, HE and AE are non-zero force member as there are directly transmitting load from the external support. So, by option elimination we can say that the answer is (a).
7. What will the magnitude of force (in N) transmitted by FI?
a) 0
b) 1
c) 2
d) 3
Answer: a
Clarification: GF is a zero force member as stated in earlier question. Now, in joint F, BF and FH are in a line. This means that the only remaining member FI which is not in line will transmit zero force.
8. What will the magnitude of force (in N) transmitted by IC?
a) 0
b) 1
c) 2
d) 3
Answer: a
Clarification: IH is a zero member force as is FI. So, IC too will be zero force members.
9. What is total no. of zero force members in the above given system?
a) 7
b) 8
c) 9
d) 10
Answer: c
Clarification: Following are the zero force member based on the logics explained above: – GF, HI, HJ, ED, FI, IC, CH, JE and JC.