Exam 1

Question 1

If the forces in a structure can be determined
using only equations of equilibrium, then the
structure is referred as statically __________

Answer 1

Determinate

Question 2

__________ = Number of unknown member forces and support reactions

Answer 2

U

Question 3

__________ = Number of possible equations of equilibrium

Answer 3

E

Question 4

If U = E then the structure is statically __________

Answer 4

Determinate

Question 5

If U > E then the structure is statically __________

Answer 5

Indeterminate

Question 6

Degree of Indeterminacy = __________

Answer 6

U - E

Question 7

Beams:
U = r (r is the number of _____ _____)
E = _____ (ΣFx = ΣFy = ΣMo = 0)

Answer 7

Support Reactions

3

Question 8

Trusses:
U = r + m (m is the # ________ of in a truss)
E = 2j (j is the number of _______ in a truss)

Answer 8

Members

Joints

Question 9

Frames:
U = r + 3m (m is the # ______ of in a frame)
E = 3j (j is the number of ______ in a frame)

Answer 9

Members

Joints

Question 10

_____ or _____ joints on beams or frames reduce the degree of indeterminacy by an amount equal to the number of degree of freedoms they have

Answer 10

Pin

Roller

Question 11

If U < E, structure is __________

Answer 11

Unstable

Question 12

If U ≥ E, structure is __________ if reactive forces are either parallel or concurrent, and some components form collapsible mechanism

Answer 12

Unstable

Question 13

Number of support reactions should at least be __________ to number of equations of equilibrium for structure to be stable

Answer 13

Equal

Question 14

All support reactions should neither be __________ nor __________ for structure to be stable

Answer 14

Parallel

Concurrent

Question 15

1) Draw free-body diagram (FBD)
2) Disassemble the structure
3) Apply support reactions based on support type
4) Identify two force members if any
5) Apply external forces
6) Apply equations of equilibrium on the FBD to determine the support reactions

Answer 15

Steps to determine support reactions: