Structures · MCQ practice Beams and Trusses MCQs – Part 2
11 questions. Tap an option to check it instantly, then read the solution.
Part 2 of 2 Question 16 Medium
To determine the force in AB of the cantilever truss shown by the method of sections, the section is passed through AB, AD and ED, and moments are taken about:
A joint C B joint B C joint D D joint A
Answer: C. joint D
Take moments about D, where the other two cut members (AD and ED) meet, so they drop out and FAB is found directly.
Question 17 Easy
In the symmetrical truss shown (bottom chord A–C–B, apex D, vertical CD, base angle 30°, 3 t load at D), the force in CD is:
A 3 t compression B 3 t tension C zero D 1.5 t compression
Answer: C. zero
At joint C, AC and CB are collinear and there is no load, so the third member CD carries zero force.
Question 18 Easy
In the two-bay truss shown (top chord D–E–F, vertical EC, 5 t downward load at E, 4 t horizontal load at D), the force in EC is:
A zero B 5 t tension C 5 t compression D 4 t tension
Answer: C. 5 t compression
At E, DE and EF are horizontal; only EC is vertical, so it must carry the 5 t load: 5 t compression.
Question 19 Medium
To determine the force in BD of the truss shown (bottom chord A–C–E, top chord B–D, loads 10 t at B and 5 t at D), a section is passed through BD, CD and CE, and moments are taken about:
A joint A B joint B C joint C D joint D
Answer: C. joint C
CD and CE both pass through joint C, so moments about C eliminate them and give FBD directly.
Question 20 Easy
J is the number of joints, B the number of members and R the number of reactions. If B = 4, R = 3 and J = 4, the truss is:
A Statically determinate B Statically indeterminate and stable C Stable D Unstable
Answer: D. Unstable
Required B = 2J − 3 = 5; only 4 members → deficient → unstable.
Question 21 Easy
In a truss, it is assumed that the members are joined by:
A Rough pins B Smooth pins C Either rough or smooth pins D None of these
Answer: B. Smooth pins
Truss analysis assumes smooth (frictionless) pin joints, so no moment passes between members.
Question 22 Medium
What is the major difference between a truss and a beam?
A A beam can't transmit load in the vertical direction while a truss can B A truss can't transmit load in the vertical direction while a beam can C A beam can't transmit load in the axial direction while a truss can D A truss can't transmit load in the axial direction while a beam can
Answer: C. A beam can't transmit load in the axial direction while a truss can
A truss carries load through axial forces in its members; a beam carries load mainly by bending and shear, not axially.
Question 23 Easy
Which of the following materials is not used in making trusses?
A Wooden struts B Metal bars C Channels D Concrete
Answer: D. Concrete
Timber and steel (bars, angles, channels) are used for trusses; plain concrete is not, because it is weak in tension.
Question 24 Easy
A truss containing j joints and m members will be a simple (perfect) truss if:
A j = 2m − 3 B m = 2j − 3 C m = 3j − 2 D j = 3m − 2
Answer: B. m = 2j − 3
m = 2j − 3.
Question 25 Easy
In the cantilever truss shown (top chord A–B–C, 100 t load at B, vertical BD, members AD, ED, and CD at 30°), the force in member BC is:
A 100 t compressive B 100 t tensile C zero D indeterminate
Answer: C. zero
Joint C has only BC and CD meeting at an angle with no load: both are zero.
Question 26 Medium
A truss is completely analysed when:
A The direct stresses (forces) in all the members are found B All the external reaction components are determined C The equilibrium is satisfied D None of these
Answer: A. The direct stresses (forces) in all the members are found
Analysis of a truss means finding the axial force in every member (after the reactions). The book's printed key gives (c); see the note.
Part 2 of 2