1. CE Statics
Chapter 6 – Lecture 19

2. STRUCTURAL ANALYSIS
The main objective of chapter 6 is to use the equilibrium equations to analyze structures which are composed of pin-connected members.

3. This is a simple structure composed of three pin-connected members AB, BC and AC.
It is assumed that as long as the structure is in equilibrium, then all members are in equilibrium.
Forces at the joints (A, B, and C) can be found by applying equilibrium equations at different parts of the structure. ِA C B

4. Simple Trusses E D C B A
Joint B
Members are joined together by bolting or welding to a common plate (called guset plate)

5. Planar Trusses
Planar trusses lie in one plane ( i.e x-y plane). Forces acting on the joints and they lie in the same plane as the truss. That is why this type of trusses is considered as a two-dimensional truss.

6. Assumptions for Design
To design a truss, it is necessary to find the force that will develop in each member at certain loading conditions. To do that, the following two assumptions are made:
All loadings are applied at the joints
Weight of members is neglected
If weight is to be considered, then it has to be divided equally at both ends
The members are joined together by smooth pins
If welding or bolting to a common plate was used, then the center lines of connecting members must be concurrent

7. Assumptions for Design

8. Assumptions for Design
Each truss member acts as a two-force member
If the force tends to elongate the member, then it is a tensile force (T)
If the force tends to shorten the member, then it is a compressive force (C)
Compression
Tension

9. Simple Truss
Simple truss is constructed by starting with a basic triangular element such as the ABC truss below. C B A