FRAMES ES 11 – Statics of Rigid Bodies Lecture 15

FRAMES

A frame is a rigid structure which is made up of members at least one of which is not a two-force member.

FRAMES

A frame is said to be rigid if it maintains it shape when it is detached from its supports.

4

5

6

500 N

C A

B

2 m

2 m

45°

B

500 N

500 N

500 N 707.1 N

Tens

ion

Recall: Method of Joints for trusses

Force by a member on the joint is directed along the member.

7

500 N

C A

B

2 m

2 m

45°

B

500 N ABX

ABX

ABY

BCY

BCX

BCY

BCX

ABX = BCX = BX

ABY = BCY = BY

AY

AX

CY

100 N 100 N

ABY

“Method of Joints” for frames

Force by a member on the joint is NOT NECESSARILY directed along the member.

EXAMPLE

Determine the horizontal and vertical components of the reaction at pin A.

EXAMPLE

Determine the horizontal and vertical components of reaction which the pins exert on member ABC.

EXAMPLE

Determine the force that the smooth roller C exerts on member AB.

500 N

C A

B

2 m

2 m

45°

100 N

If a force is applied on a joint connecting two or more members, choose a member where the force will be included.

200 N

The choice of member may affect the other unknown forces, but not the internal forces in the members.

500 N BX

BY BY

BX

AY

AX

CY

100 N

200 N

500 N BX

BY BY

BX

AY

AX

CY

100 N

200 N

OR

EXAMPLE

Determine the horizontal and vertical components of reaction which the pins exert on member ABC.