How to calculate the normal stress of a Howe reinforcement?

In summary: These are not beams. This is a pin-connected truss made up of struts that can only support tension or compression. There are no bending stresses. The main principal stress of each strut is oriented along the strut, and the other two principal stresses are zero. To get the stress in each strut, you need to know its cross sectional area.To calculate the stress in a strut, you need to know its cross sectional area.
  • #1
Tapias5000
46
10
Homework Statement
I am asked to calculate the forces of the bars specifying if it is in compression or tension, then I am asked to calculate the normal stress in all the bars.
Relevant Equations
Σfx=0 and Σfy=0
This is the structure
?hash=6ba799a1c24ecd69f272a427f67e6857.png

I already made the calculation of all the bars T = tension and C = compression, these are the results.

Imagen7.png

now I am asked to calculate the normal stress in all the bars but I don't understand where to start, could you tell me how? here is the diagram of the first node but I really don't know where to start.
Imagen8.png
 

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  • #2
Tapias5000 said:
calculate the normal stress
Don't you need to know the cross-sectional area of the bars for that?
 
  • #3
haruspex said:
Don't you need to know the cross-sectional area of the bars for that?
It seems that way, I looked for a lot of information and most of the exercises had the data of the normal effort, or the area or some other, here I have nothing that.

I don't know if because they are "triangles" I should calculate their area through centroids.

I also have to choose the material of this structure, some type of beam, I don't know if by choosing it I will obtain any data to calculate it, but if I follow the order, they first ask me to calculate the normal stress and then choose a beam for the structure.

I also found information on a method called normal bending stress, where none of this data is available, but I did not find any example that did it with a structure like this or similar.

I'm really very confused ...
 
  • #4
Tapias5000 said:
It seems that way, I looked for a lot of information and most of the exercises had the data of the normal effort, or the area or some other, here I have nothing that.

I don't know if because they are "triangles" I should calculate their area through centroids.

I also have to choose the material of this structure, some type of beam, I don't know if by choosing it I will obtain any data to calculate it, but if I follow the order, they first ask me to calculate the normal stress and then choose a beam for the structure.

I also found information on a method called normal bending stress, where none of this data is available, but I did not find any example that did it with a structure like this or similar.

I'm really very confused ...
Sounds like an error in the question. Is there a list of beams to choose from? If so, does it specify only the material, or material and section?
 
  • #5
haruspex said:
Sounds like an error in the question. Is there a list of beams to choose from? If so, does it specify only the material, or material and section?
no, I'm supposed to look for and choose the beam too
 
  • #6
Tapias5000 said:
no, I'm supposed to look for and choose the beam too
Then all you need is the forces you calculated.
My guess is the part asking for normal stress is left over from an earlier version of the question.
 
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  • #7
haruspex said:
Then all you need is the forces you calculated.
My guess is the part asking for normal stress is left over from an earlier version of the question.
Ok, so there is no other method to calculate the normal stress without having at least one data? I just follow the order of the points and first is to calculate the normal stress and then choose a beam.

First I would have to look for information about a beam and then calculate the normal stress then?
 
  • #8
Tapias5000 said:
Ok, so there is no other method to calculate the normal stress without having at least one data? I just follow the order of the points and first is to calculate the normal stress and then choose a beam.

First I would have to look for information about a beam and then calculate the normal stress then?
Each material will have a safe normal stress limit, and from that and the force you can calculate the required cross-section.
 
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  • #9
I don't understand the meaning of "the normal stress in all the bars".
Could you show us the whole text of the problem?
 
  • #10
Tapias5000 said:
Ok, so there is no other method to calculate the normal stress without having at least one data? I just follow the order of the points and first is to calculate the normal stress and then choose a beam.

First I would have to look for information about a beam and then calculate the normal stress then?
These are not beams. This is a pin-connected truss made up of struts that can only support tension or compression. There are no bending stresses. The main principal stress of each strut is oriented along the strut, and the other two principal stresses are zero. To get the stress in each strut, you need to know its cross sectional area.
 
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  • #11
Lnewqban said:
I don't understand the meaning of "the normal stress in all the bars".
Could you show us the whole text of the problem?
"Normal stress" is the force along the bar divided by its cross sectional area, i.e. stress normal to the cross section.
 
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1. What is normal stress in a Howe reinforcement?

Normal stress in a Howe reinforcement refers to the amount of force per unit area that is applied perpendicular to the cross-sectional area of the reinforcement. It is a measure of the internal forces that are present within the reinforcement due to external loading.

2. How do I calculate the normal stress of a Howe reinforcement?

To calculate the normal stress of a Howe reinforcement, you will need to know the applied force, the cross-sectional area of the reinforcement, and the orientation of the force relative to the reinforcement. The formula for normal stress is stress = force/area, where force is in Newtons (N) and area is in square meters (m^2).

3. What are the units for normal stress?

The units for normal stress are typically expressed in Pascals (Pa) or Megapascals (MPa). These are both units of pressure, with 1 MPa equal to 1 million Pa.

4. How does normal stress affect the strength of a Howe reinforcement?

Normal stress is a measure of the internal forces within a reinforcement, and it directly affects the strength of the reinforcement. Higher normal stress values indicate that the reinforcement is experiencing more force per unit area, which can lead to deformation or failure if the stress exceeds the strength of the material.

5. Are there any safety factors to consider when calculating normal stress in a Howe reinforcement?

Yes, it is important to consider safety factors when calculating normal stress in a Howe reinforcement. These factors take into account potential uncertainties and variations in the applied force and material strength, and they ensure that the reinforcement can safely withstand the expected load without failure. The specific safety factor to use will depend on the application and industry standards.

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