CE 201 - Statics

1. CE 201 - 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. B ِA C • 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.

4. E D A C B Simple Trusses 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. Compression Tension 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)

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