Priodeep Chowdhury;Lecturer;Dept. of CEE;Uttara University//TRUSS Page 1 T R U S S A truss is a structure that consists of All straight members connected together with pin joints connected only at the ends of the members and All external forces (loads & reactions) must be applied only at the joints. A truss is a structure composed of slender members joined together at their end points . Each member only takes axial forces. Truss –– Assumptions There are four main assumptions made in the analysis of truss. Truss members are connected together at their ends only. Trusses are connected together by frictionless pins. The truss structure is loaded only at the joints. The weights of the members may be neglected. Types of Trusses Simple Trusses: The basic building block of a truss is a triangle. Large truss are constructed by attaching several triangles together a new triangle can be added truss by adding two members and a joint. A truss constructed in this fashion is known as a simple truss. Other Types:
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Priodeep Chowdhury;Lecturer;Dept. of CEE;Uttara University//TRUSS Page 1
T R U S S
A truss is a structure that consists of
All straight members
connected together with pin joints
connected only at the ends of the members and
All external forces (loads & reactions) must be applied only at the joints.
A truss is a structure composed of slender members joined together at their end points.
Each member only takes axial forces.
Truss –– Assumptions
There are four main assumptions made in the analysis of truss.
Truss members are connected together at their ends only.
Trusses are connected together by frictionless pins.
The truss structure is loaded only at the joints.
The weights of the members may be neglected.
Types of Trusses
Simple Trusses: The basic building block of a truss is a triangle. Large truss are constructed by attaching
several triangles together a new triangle can be added truss by adding two members and a joint. A truss
constructed in this fashion is known as a simple truss.
Other Types:
Priodeep Chowdhury;Lecturer;Dept. of CEE;Uttara University//TRUSS Page 2
METHODS OF SOLVING TRUSS
Method of Joints
• Principle
If a truss is in equilibrium, then each of its joints must also be in equilibrium. The truss is made up of
single bars, which are either in compression, tension or no-load. The means of solving force inside of the truss
use equilibrium equations at a joint. This method is known as the method of joints.
• Procedure
starts with a joint that has no more than two unknown forces
Establish the x and y axis;
At this joint, ∑ Fx = 0 and ∑ Fy = 0;
After finding the unknown forces applied on this joint, these forces become the given values in the
analysis of the next joints.
• Tips
- The joints with external supports always connect with two truss members. Thus many times, the analysis
starts from analyzing the supports. Therefore very often the analysis begins with finding the reaction forces
applied at the supports.
- Pay attention to symmetric systems and zero-force members. Identification of these special cases sometimes
will make the whole analysis WAY EASIER!!
Priodeep Chowdhury;Lecturer;Dept. of CEE;Uttara University//TRUSS Page 3
Zero Force Members:
(a) If only two no collinear members are connected to a joint that has no external loads or reactions applied to it,
then the force in both members is zero.
(b) If three members, two of which are collinear, are connected to a joint that has no external loads or reactions
applied to it, then the force in the member that is not collinear is zero.
Zero Member Force Calculations
Priodeep Chowdhury;Lecturer;Dept. of CEE;Uttara University//TRUSS Page 4