# Can a 25kN Force Affect the Moment at the Fixed Support in Beam Analysis?

• PK1248
In summary, the student is trying to solve for unknown reactions and producing the Bending Moment Diagram and Shear Force Diagram. They are having difficulty understanding the force generated by the 25kN force, and are seeking help from someone who may be more knowledgeable about the subject.
PK1248

## Homework Statement

Okay, I am required to analyse the beam solving for all unknown reactions, both internal and external. From there, the Bending Moment Diagram and Shear Force Diagram are to be produced.

## The Attempt at a Solution

So i sectioned the beam at the internal hinge and using the left hand beam and statics, was able to determine the shear at the hinge to be 20kN. From that, i was able to determine the reaction at the roller (80kN upwards).

On the right hand beam, i have taken moments about the fixed support. I have a moment supplied by the shear (60kNm clockwise) and a moment supplied at the fixed support (M) as well as the moment applied by the bent member.

That relates to the issue. I'm confused as to the moment generated by the 25kN force. I feel as though the 2.5m dimension on the right of the image is a red herring. That is, the force acts vertical and so by definition, there would be no moment as the force acts parallel to the 2.5m dimension.

Any help would be greatly appreciated

#### Attachments

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If you are not certain, you can always calculate the vector product r x F, where r is the position of F w.r.t. the attachment point on the beam.

Does this help? Add a 25 kN force downwards at E, and then add another 25 kN Force upwards at E. You then have a force and a couple.

quote "On the right hand beam, i have taken moments about the fixed support. I have a moment supplied by the shear (60kNm clockwise) and a moment supplied at the fixed support (M) as well as the moment applied by the bent member."
Don't forget the effect of the reaction at B.

(This makes an interesting question in qualitative analysis. From the bending moment diagram you should be able to determine the deflected shape and whether the hinge at C goes up or down, without calculation)

.

As a scientist, it is important to carefully analyze all aspects of a problem before coming to a conclusion. In this case, it seems that the 25kN force may not actually contribute to the moment at the fixed support because it is acting parallel to the 2.5m dimension. However, it is important to consider the possibility that this force may have a component that is perpendicular to the 2.5m dimension, which would contribute to the moment. It may also be helpful to consider the direction of the force and how it affects the overall equilibrium of the beam. I would suggest double-checking your calculations and considering all possible factors before making a final determination. Additionally, seeking guidance from a professor or experienced engineer may also be beneficial in solving this problem.

## What is a determinate beam?

A determinate beam is a structural element that is supported at two or more points and is able to resist loads and moments without undergoing any appreciable deformation. It is a common type of structural member used in construction.

## What is the purpose of analyzing a determinate beam?

The purpose of analyzing a determinate beam is to determine the internal forces and moments that are present within the beam when it is subjected to external loads. This information is crucial in designing and constructing safe and efficient structures.

## How is a determinate beam analyzed?

A determinate beam is typically analyzed using the principles of statics and mechanics of materials. This involves calculating the reactions at the supports, determining the internal forces and moments at different points along the beam, and checking for equilibrium and compatibility between the external loads and internal forces.

## What are the common types of loads that a determinate beam may experience?

A determinate beam can experience a variety of loads, including point loads, distributed loads, and moments. These loads can be further categorized as either external or internal, depending on whether they act on the beam from the outside or are generated within the beam itself.

## What are the key assumptions made in the analysis of a determinate beam?

The key assumptions made in the analysis of a determinate beam include that the beam is straight and has constant cross-section, that the material is homogeneous and isotropic, and that the beam is subjected to static loads only. These assumptions allow for the use of simplified equations and methods in the analysis process.

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