Homework check - Mohr's circle & Shear stress in I beam

In summary, the conversation discussed two homework questions - one regarding Mohr's circle and the other regarding shear stress in an I beam. For the Mohr's circle question, there were conflicting examples and confusion about the direction of rotation from the Y axis. For the shear stress in an I beam question, there was uncertainty about whether the maximum shear force should be taken from the shear force diagram or from the point load. The equations used for these questions were Mohr's Circle and I = d . b^3 / 12 and tmax = (F / I . b) . (A1 . y1) + (A2 . y2) respectively. The corresponding working for each question was provided in the conversation.
  • #1
ridiculoid
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Homework Statement



Mohrs circle question - https://imgur.com/SKeTUXN

Shear stress in I beam question - https://imgur.com/34yTyCA

Homework Equations



Mohrs Circle - None

Shear stress in I beam - I = d . b^3 / 12
tmax = (F / I . b) . (A1 . y1) + (A2 . y2)

The Attempt at a Solution



For the Mohr's circle question, I have drawn 2 induced loading elements (shown at the bottom of of my working) I just seem to have conflicting information from some class examples and am wondering whether I take the 78° clockwise or anticlockwise from the Y axis of the element.

Mohrs circle working - https://imgur.com/YPtVNSb

In the shear stress in an I beam question, It is asking for the maximum shear FORCE in the beam. Do I take the maximum value from the shear force diagram as shown in my working? or is the maximum shear force the 15kN at the point Load?

Shear stess in I beam working - https://imgur.com/UCAexj6
 
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  • #2
Please split this into separate threads and post the complete question as given to you in each.
 

FAQ: Homework check - Mohr's circle & Shear stress in I beam

1. What is Mohr's circle and how is it used in engineering?

Mohr's circle is a graphical representation of stress and strain in a material. It is commonly used in engineering to determine the principal stresses and maximum shear stress at a point in a material under various loading conditions.

2. How do you construct a Mohr's circle?

To construct a Mohr's circle, you need to plot the normal stress and shear stress values on a graph with the normal stress on the x-axis and shear stress on the y-axis. Then, draw a circle with a radius equal to the maximum normal stress and centered at the origin. The coordinates of the points where the circle intersects the x-axis and y-axis represent the principal stresses.

3. How do you calculate the maximum shear stress using Mohr's circle?

To calculate the maximum shear stress, you need to find the distance between the center of the circle and the point of intersection where the circle meets the x-axis or y-axis. This distance is equal to the radius of the circle and represents the maximum shear stress.

4. How is shear stress distributed in an I beam?

Shear stress in an I beam is distributed along the cross-section of the beam. The shear stress is highest at the top and bottom flanges, and decreases towards the neutral axis of the beam. This distribution of shear stress is important in determining the strength and stability of the beam.

5. How do you calculate the shear stress in an I beam?

The formula for calculating shear stress in an I beam is given by τ = VQ/Ib, where τ is the shear stress, V is the shear force acting on the beam, Q is the first moment of area of the beam's cross-section, I is the moment of inertia of the beam's cross-section, and b is the width of the beam. This formula can be used to determine the maximum shear stress at any point along the beam's cross-section.

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