Method of Sections: Ignored Forces?

[influx]

In the above example, the method of sections is used to solve the truss. However, they do not consider the forces in other beams (the beams that are not being cut; e.g. AB, AH). Is this always the case with this method?

 

[mfb]

There are no external forces coming from those beams.

 

[influx]

There are no external forces coming from those beams.

I understand but why are we not considering the internal forces eg force AH (like we are considering the internal force HG)

 

[mfb]

HG is not an internal force in this part. That's the idea - split the whole constructions in smaller parts. Some splittings work, some do not, this is a working one.

 

[rezeew]

The method of sections is a commonly used technique in structural analysis to determine the internal forces in a truss or other structural system. While it can be a useful approach, it is important to note that it does have limitations, and one of these is that it may not account for all forces present in a structure.

In the example given, the method of sections is used to solve for the internal forces in a specific section of the truss. This means that the forces in other beams, such as AB and AH, are not directly considered in the analysis. However, this does not mean that these forces are completely ignored.

In fact, the method of sections relies on the equilibrium of forces in the overall structure, including all beams and members. By solving for the internal forces in one section, we are assuming that the forces in the rest of the structure are in equilibrium and do not significantly affect the section being analyzed. This is a reasonable assumption in many cases, but it is important to consider the overall forces and loads on the structure to ensure the accuracy of the analysis.

In some cases, the method of sections may not be the most appropriate approach for analyzing a structure. For example, if there are significant external loads or moments acting on the structure, or if there are complex connections between beams, a more comprehensive analysis method may be necessary.

In conclusion, while the method of sections can be a useful tool for analyzing trusses and other structures, it is important to recognize its limitations and consider the overall forces and loads on the structure to ensure accurate results.