Determinacy for trusses

Question 1

Draw the dof of one pin?

Answer 1

Question 2

How many dof does 2 pins have?

Answer 2

Question 3

How many dof does two pins, one bar have?

Answer 3

Question 4

How many dof does 3 pins, 1 bar have?

Answer 4

Question 5

How many dof does 3 pins, 2 bars have?

Answer 5

Question 6

Determine if this structure is statically determinate truss

Answer 6

No of pins: 6
No of bars: 9
No of reactions: 3

6 x 2 =12 dof
12 - 9 - 3 =0 0
No of dof generated - no of dof removed = this truss is statically determinate

Question 7

Determine if this structure is statically determinate?

Answer 7

No of pins: 10
No of bars: 18
No of reactions: 3
No of dof generated - no of dof removed =
10 x 2 - 18 - 3 = -1
This truss is statically determinate. One of the diagonal braces is unnecessary, creating redundancy in the truss

Question 8

Determine if this structure is statically determinate?

Answer 8

No of pins: 10
No of bars: 18
No of reactions: 3
No of dof generated - no of dof removed =
10 x 2 - 18 - 3 = -1
This truss is statically determinate. One of the diagonal braces is unnecessary, creating redundancy in the truss

Question 9

Determine if this structure is statically determinate?

Answer 9

No of pins: 6
No of bars: 9
No of reactions: 3
6 x 2 - 9 - 3 = 0
No of dof generated - no of dof removed = 0
This would suggest that the truss is statically determinate BUT this is actually a mechanism because it is over constrained

Question 10

Using the “method of sections” work out the forces of this truss

Answer 10