Statics: Method of Joints (Truss)

Thread starter Vanessa Avila
Start date Mar 26, 2017
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Joint Joints Method Method of joints Statics Truss Trusses

In summary, the Method of Joints is a commonly used approach in statics to analyze the forces acting on a truss. It involves breaking down the truss into individual joints and using the equations of equilibrium to solve for the unknown forces at each joint. This process is repeated until all the unknown forces are determined and the overall equilibrium and stability of the truss can be checked. The method makes certain assumptions such as the truss being loaded only at the joints and being in a state of static equilibrium. It has advantages such as being a simple and systematic approach that can be applied to trusses with any number of joints and members. However, there are also common errors to avoid such as not considering all external forces or incorrectly labeling the forces

Mar 26, 2017

Vanessa Avila

Can someone explain to me why that highlighted force is 0?

Homework Equations

∑Fx = 0

The Attempt at a Solution

I found F_DC to be 780lb and I am still trying to solve for F_DE

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Mar 26, 2017

PhanthomJay

Science Advisor

Homework Helper

Gold Member

If BD was non zero, let's just say for example it was 100 pounds , then 100 lbs in the opposite direction would be required for equilibrium along that axis. Where would that required opposite force go?

What is the "Method of Joints" in statics?

The Method of Joints is a common approach used in statics to analyze the forces acting on the different members of a truss. It involves breaking down the truss into individual joints and analyzing the forces acting at each joint to determine the overall stability and equilibrium of the truss.

What are the basic steps for using the Method of Joints?

The basic steps for using the Method of Joints are as follows:

Determine the external forces acting on the truss.
Identify all the joints in the truss.
Choose a joint to analyze and draw a free body diagram of that joint.
Apply the equations of equilibrium to solve for the unknown forces at that joint.
Repeat this process for each joint until all the unknown forces in the truss have been determined.
Check for overall equilibrium and stability of the truss.

What are the assumptions made in the Method of Joints?

The Method of Joints makes the following assumptions:

The truss is loaded only at the joints.
The joints are considered to be perfectly pinned and can only support axial forces (tension or compression).
The members of the truss are considered to be weightless.
All external forces acting on the truss are applied at the joints.
The truss is in a state of static equilibrium.

What are the advantages of using the Method of Joints?

The Method of Joints has several advantages:

It is a simple and systematic approach for analyzing truss structures.
It can be used for both statically determinate and indeterminate trusses.
It only requires knowledge of the external forces and geometry of the truss.
It can be easily applied to trusses with any number of joints and members.
It can provide a visual representation of the forces acting on each member of the truss.

What are some common errors to avoid when using the Method of Joints?

Some common errors to avoid when using the Method of Joints are:

Not considering all the external forces acting on the truss.
Incorrectly labeling the forces at the joints as either tension or compression.
Not applying the equations of equilibrium correctly.
Assuming that the truss is in equilibrium without checking for overall stability.
Not taking into account the effects of member weight and/or self-weight of the truss.