A truss is a structure that is made up of interconnected members that are subjected to external forces. It is commonly used in the construction of bridges, roofs, towers, and other structures. The members of a truss can be in tension or compression depending on the direction of the external forces. In this article, we will discuss how to determine the force in each member of the truss and state if it is in tension or compression.
Types of Trusses
Before we dive into the calculations, let us first discuss the different types of trusses. There are several types of trusses, including the Pratt truss, Howe truss, Warren truss, and others. Each truss has a unique design and is used for specific applications. However, the basic principles of calculating the force in each member apply to all types of trusses.
Method of Joints
The method of joints is one of the most common methods used to determine the force in each member of a truss. This method involves analyzing each joint of the truss and calculating the force in each member connected to that joint. The steps involved in the method of joints include:
- Identify the external forces acting on the truss.
- Draw the free-body diagram of the entire truss.
- Calculate the support reactions at each end of the truss.
- Choose a joint and draw its free-body diagram.
- Apply the equilibrium equations to the joint to calculate the force in each member.
- Repeat steps 4 and 5 for each joint of the truss.
Method of Sections
The method of sections is another common method used to determine the force in each member of a truss. This method involves cutting a section of the truss and analyzing the forces acting on that section. The steps involved in the method of sections include:
- Identify the external forces acting on the truss.
- Draw the free-body diagram of the entire truss.
- Choose a section of the truss and cut it.
- Draw the free-body diagram of the cut section.
- Apply the equilibrium equations to the cut section to calculate the force in each member.
- Repeat steps 3-5 for each section of the truss.
Tension and Compression
Members of a truss can be in tension or compression depending on the direction of the external forces. Tension is a force that pulls a member apart, while compression is a force that pushes a member together. To determine if a member is in tension or compression, we need to analyze the direction of the force acting on that member. If the force is pulling the member apart, it is in tension. If the force is pushing the member together, it is in compression.
Conclusion
Determining the force in each member of a truss is essential in ensuring that the truss is structurally stable and can withstand external forces. The method of joints and method of sections are two common methods used to calculate the force in each member of a truss. Additionally, understanding the difference between tension and compression is crucial in determining the type of force acting on each member of the truss. By following these principles, we can ensure that trusses are designed and constructed in a safe and reliable manner.
