ME 214 Vector Statics
Chapter 6
Instructor: A Rezaei
Today’s Objective: Students will be able to:
Students will be able to:
a)
Define a simple truss.
b)
Determine the forces in members of a simple truss.
c)
Identify zeroforce members.
a) Define a Simple Truss
•
A truss
is a structure composed of slender members joined together at their end points.
•
If a truss, along with the imposed load, lies in a single plane
(as shown at the top right), then it is called a planar truss
.
•
A
simple truss
is a planar truss which begins with a triangular element and
can be expanded by adding two members and a joint. For these trusses, the number of
members (M) and the number of joints (J) are related by the equation
M
=
2 J
–
3.
b) THE METHOD OF JOINTS
1
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View Full DocumentSTEPS FOR ANALYSIS of Trusses using the Method of Joints
1.
If the support reactions are not given, draw a FBD of the entire truss and determine all the support
reactions using the equations of equilibrium.
2.
Draw the freebody diagram of a joint with one or two unknowns.
Assume that all unknown member
forces act in tension (pulling the pin)
unless you can determine by inspection that the forces are
compression loads.
3.
Apply the scalar equations of equilibrium,
∑
F
X
=
0
and
∑
F
Y
=
0, to determine the unknown(s).
If
the answer is positive
, then the assumed direction (tension
) is correct, otherwise it is in the opposite
direction (compression).
4.
Repeat steps 2 and 3 at each joint in succession until all the required forces are determined.
Example 1
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 Summer '06
 Lipovetsky
 Statics, Truss, FBD

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