Two force and multiforce members
Structures VS Machines
Usually fixed in position
Structures
Designed to support applied loads
Machines Moving parts
Perform useful mechanical work
Transforming input forces
Frames
Stationary structures that supportloads
An assembly of rigidmembers ofwhich at least one is a multiforce member
Members arejoined bypintypeconnections to form a frame
Theloads can be applied anywhere on a frame
Twoforce members
Experience forces only at their twofrictionlessendsandcarry noload in between
Members are assumed to be weightless
If two forces are equalandopposite equilibrium isachieved
If straight members experience onlyaxial
tension or compression forces
If carved or kinked combination ofaxial
shear and bendingforces
Multi force members
Pbreeforce members single resultantforce
replacingmultipleappliedforces
In general a member that is loaded transversely
Such experiences internalshearandbendingforces as a resultoftheloading
, Two members FrameExamples
Horizontal only members
NOTE
1 For a framecomprising N membersthere
will be N I sets of equilibrium
equations and N 1 free body
diagrams
2 If all external reactions in a frame can be determined then the internal forces
between members can be determined from eithermember
FBD
3 If there are more unknowns than availableequationsthenthesystemis usually
considered to be Statically Indeterminate
skippth
Am
GKN
Ay YkN
cy
Efx 0 Ax 6 0
Are GKN
Fy 0 Aytcy 170
M o M A 0
Am 82 8 5 6cg o
Structures VS Machines
Usually fixed in position
Structures
Designed to support applied loads
Machines Moving parts
Perform useful mechanical work
Transforming input forces
Frames
Stationary structures that supportloads
An assembly of rigidmembers ofwhich at least one is a multiforce member
Members arejoined bypintypeconnections to form a frame
Theloads can be applied anywhere on a frame
Twoforce members
Experience forces only at their twofrictionlessendsandcarry noload in between
Members are assumed to be weightless
If two forces are equalandopposite equilibrium isachieved
If straight members experience onlyaxial
tension or compression forces
If carved or kinked combination ofaxial
shear and bendingforces
Multi force members
Pbreeforce members single resultantforce
replacingmultipleappliedforces
In general a member that is loaded transversely
Such experiences internalshearandbendingforces as a resultoftheloading
, Two members FrameExamples
Horizontal only members
NOTE
1 For a framecomprising N membersthere
will be N I sets of equilibrium
equations and N 1 free body
diagrams
2 If all external reactions in a frame can be determined then the internal forces
between members can be determined from eithermember
FBD
3 If there are more unknowns than availableequationsthenthesystemis usually
considered to be Statically Indeterminate
skippth
Am
GKN
Ay YkN
cy
Efx 0 Ax 6 0
Are GKN
Fy 0 Aytcy 170
M o M A 0
Am 82 8 5 6cg o
