Trusses
1.[2p] Why does an idealised truss member carry axial force only?
Why does an idealised truss member carry axial force only?
The answer is: Forces act on it at two points alone, and two forces can only balance if they are equal, opposite and along the line joining them
The answer is: Forces act on it at two points alone, and two forces can only balance if they are equal, opposite and along the line joining them
The answer is: Forces act on it at two points alone, and two forces can only balance if they are equal, opposite and along the line joining them
2.[3p] A three-bar truss has supports at (0, 0) and (12, 0) and an apex at (6, 8), all in metres, and carries 30 kN at the apex. What is the tension in the bottom chord, in kN?
A three-bar truss has supports at (0, 0) and (12, 0) and an apex at (6, 8), all in metres, and carries 30 kN at the apex. What is the tension in the bottom chord, in kN?
3.[2p] Three members meet at an unloaded joint and two of them are collinear. How many of the three carry zero force?
Three members meet at an unloaded joint and two of them are collinear. How many of the three carry zero force?
4.[2p] A determinate planar truss has 10 joints, a pin at one support and a roller at the other. How many members does it have?
A determinate planar truss has 10 joints, a pin at one support and a roller at the other. How many members does it have?
5.[1p] A member that carries zero force under the analysed load case can safely be left out of the built structure.
A member that carries zero force under the analysed load case can safely be left out of the built structure.
The answer is: False
6.[3p] Which assumptions turn a real framework into an analysable truss?
Which assumptions turn a real framework into an analysable truss?
Select all that apply
The answer is: Every joint is a frictionless pin that transmits no moment, All loads are applied at the joints, Members are straight, and their self-weight is small or split between their end joints
7.[2p] Why is a moment point chosen at the intersection of two of the three cut members?
Why is a moment point chosen at the intersection of two of the three cut members?
The answer is: Both of those forces pass through it, so the remaining unknown stands alone in one equation
The answer is: Both of those forces pass through it, so the remaining unknown stands alone in one equation
The answer is: Both of those forces pass through it, so the remaining unknown stands alone in one equation
8.[3p] In the six-panel Pratt truss of the lesson, match each member to what it carries.
In the six-panel Pratt truss of the lesson, match each member to what it carries.
End diagonal
Top chord at midspan
Bottom chord at midspan
Vertical at midspan
128 kN tension
zero
144 kN compression
100 kN compression
Show the answer
End diagonal: 100 kN compression Top chord at midspan: 144 kN compression Bottom chord at midspan: 128 kN tension Vertical at midspan: zero
9.[3p] Why do the chord forces in a truss grow towards midspan while the diagonal forces shrink?
Why do the chord forces in a truss grow towards midspan while the diagonal forces shrink?
The answer is: The chords carry the bending moment and the diagonals carry the shear, and those peak at opposite ends of the span
The answer is: The chords carry the bending moment and the diagonals carry the shear, and those peak at opposite ends of the span
The answer is: The chords carry the bending moment and the diagonals carry the shear, and those peak at opposite ends of the span