1. STRUCTURAL ANALYSIS
Simple Truss
A truss is a structure composed of slender members joined together t their end points. The members
commonly used in construction consist of wooded struts or metal bars. The joint connection are usually
formed by bolting or welding the ends of the members to a common plate, called a gusset plate, (Figure
1) or by simply passing a large bolt or pin through each member (Figure 2).
Assumptions for Design
To design both the members and the connections of a truss, it is first necessary to determine the force
developed in each member when the truss is subjected to a given loading. In this regard, two important
assumptions will be made:
(1) All loadings are applied at the joints. In most situations, such as for bridge and roof trusses, this
assumption is true. Frequently in the force analysis the weight of the member is neglected since
the forces supported by the members are usually large in comparison to their weight.
(2) The members are joined together by smooth pins. In cases where bolted or welded joint
connections are used, this assumption is satisfactory provided the center lines of joining
members are concurrent.
Two methods used for truss analysis
a. Methods of joints
b. Methods of sections
THE METHOD OF JOINTS
In order to analyze or design a truss, we must obtain the force in each of its members. If we were to
consider a free-body diagram of the entire truss, then the forces in the members would be internal
forces, and they could not be obtained from an equilibrium analysis. Instead, if we consider the
equilibrium of a joint of the truss then a member force becomes an external force on the joint’s free-
body diagram, and the equations of equilibrium can be applied to obtain its magnitude. This forms the
basis for the method of joints.

2. Example 1:
Determine the force in members GE, GC and BC of the truss shown in the figure. Indicate whether the
members are in tension or compression.
SOLUTION:

3. __________________________
__________________________

4. __________________________
Example 2:
Determine the force in members in BF, BG and AB, and state if the members are in tension or
compression.

5. SOLUTION:

6. Hence, reactions at A and G;