Shear force and bending moment diagrams

In summary, The conversation discusses drawing shear force and bending moment diagrams for a simply supported beam and determining the values of the greatest shear force and bending moment, as well as the bending moment at point D. The person asking for help has attempted to solve for the values but is unsure if they are correct and asks for assistance. The other person suggests taking moments from point A and labeling points on the SFD to determine the bending moment at point D.
  • #1
Stacyg
25
0
Hi. The question is:
Draw the shear force and bending moment diagrams for the simply supported beam shown below. State the values of the greatest shear force and bending moment, and the bending moment at D.
The diagram is attached as is my attempt at the answer. I hvae not stated the values of greatest shear force, bending moment or shown the bending moment at D as I am not sure how to do this.
Also with my Bending moment diagram I am not sure if I have started it right.
Any help would be great thanks.
 

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  • #2
It's been awhile since I've done this but hopefully I can help a little.

I can't read your SFD too well, but to solve for the bending moment at D..

Take moments from point A

Ma = 0 kn . mm
Mb = 0 + (Length x Width on your SFD)

The bending moment at D will be Mc + (Bound area from C-D)

Labeling the points on your SFD should help you out with this.
 
  • #3


Hi there,

Shear force and bending moment diagrams are graphical representations of the internal forces and moments acting on a beam. They are important tools used in structural analysis and design.

To draw the shear force and bending moment diagrams for the simply supported beam shown, we first need to determine the reactions at the supports. Since the beam is simply supported, the reactions at each support will be equal and opposite.

Let's label the reactions as RA and RB. By taking moments about point A, we can determine that RA = 10 kN and RB = 20 kN. These reactions will be shown on our diagrams as point loads acting upwards at A and B.

Next, we can draw the shear force diagram by starting at the left end of the beam and moving to the right. At point A, the shear force is equal to RA = 10 kN, so we draw a horizontal line at this value. As we move towards the middle of the beam, the shear force decreases linearly until we reach point B, where it becomes zero. This is because there are no external forces acting on the beam between A and B.

At point B, the shear force suddenly increases to RB = 20 kN and remains constant until the end of the beam. This is because the reaction at B is acting upwards to counteract the downward force of the beam's own weight.

Next, we can draw the bending moment diagram by starting at the left end of the beam and moving to the right. At point A, the bending moment is zero. As we move towards the middle of the beam, the bending moment increases parabolically until we reach point B, where it is equal to the product of the reaction RB and the distance from B to the end of the beam.

At point B, the bending moment suddenly decreases to zero and then remains constant until the end of the beam. This is because the reaction at B creates an equal and opposite moment to counteract the bending moment caused by the weight of the beam.

The greatest shear force occurs at point B, where it is equal to RB = 20 kN. The greatest bending moment also occurs at point B, where it is equal to RB multiplied by the length of the beam.

To find the bending moment at point D, we can use the equation M = Wx, where W is the force acting on the beam and x is the distance from the point of interest. In this case, the force acting on the
 

FAQ: Shear force and bending moment diagrams

What is a shear force diagram?

A shear force diagram is a graphical representation of the variation of shear force along the length of a structural member, such as a beam or column. It shows the magnitude and direction of the internal forces acting on the member at different points.

What is a bending moment diagram?

A bending moment diagram is a graphical representation of the variation of bending moment along the length of a structural member, such as a beam or column. It shows the magnitude and direction of the internal forces caused by external loads acting on the member at different points.

How are shear force and bending moment diagrams related?

Shear force and bending moment diagrams are related because the shear force at a point in a structural member is equal to the slope of the bending moment diagram at that point. This means that changes in shear force will result in changes in bending moment and vice versa.

What information can be determined from shear force and bending moment diagrams?

Shear force and bending moment diagrams provide important information about the internal forces and stresses in a structural member. They can help determine the maximum and minimum values of shear force and bending moment, as well as the location and magnitude of points of zero shear and zero moment. This information is crucial for designing safe and efficient structures.

How are shear force and bending moment diagrams used in structural analysis and design?

Shear force and bending moment diagrams are used in structural analysis and design to determine the internal forces and stresses in a structural member and ensure that the member can withstand the applied loads. They are also used to determine the size and shape of structural members and to identify potential failure points. These diagrams are essential tools for engineers and architects in designing safe and efficient structures.

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