Shear & Bending Moment Diagrams

In summary, the conversation discusses confusion with approaching shear and bending moment diagrams from the right versus left side of a beam. It is mentioned that in a cantilever, starting at the free end makes the boundary conditions easier to deal with, while in a simply supported beam it doesn't make much difference. It is also noted that a symmetrical beam may not have symmetrical V and M diagrams and suggests drawing diagrams to understand loading.
  • #1
skaterbasist
13
0
I apologize for not using the template, but my question is more of a conceptual question than anything else.

The only thing so far that confuses me with Shear and Bending Moment Diagrams is when, in some cases, it is easier to approach the beam from the right side instead of the left.

When you do so, how does the graph change? Is it "mirrored"? If so, are both the shear & moment diagrams mirrored about the Y axis or X axis? Does it matter if the problem is cantilevered or simply supported in terms of the above asked question?

Thank you for any assistance. I have been stuck with this scenario in my head all day long. :eek:
 
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  • #2
It's not so much right and left as - well, in a cantilever, if you start x=0 at the free end of the cantilever, you don't need to initially work out the reactions. If you are using the method of integration, the boundary conditions are easier to deal with at the free end than at the encastre end. However in a simply supported beam, it doesn't make much difference, because you really do need those reactions before you start the shear force or bending moment diagrams. A symmetrical beam will not necessarily have symmetrical V and M diagrams. One way for you to learn, after having covered basic cases, is to draw some symmetrical V and M diagrams, and work out what loading would have produced such diagrams.
 

1. What is a shear and bending moment diagram?

A shear and bending moment diagram is a graphical representation of the distribution of forces and moments along a structural member, such as a beam or column. It shows the magnitude and direction of the shear and bending forces at different points along the member.

2. How do you construct a shear and bending moment diagram?

To construct a shear and bending moment diagram, you first need to determine the reactions at the supports and any point loads or distributed loads acting on the member. Then, you can use the equations of equilibrium and shear and moment equations to calculate the shear and bending moment at different points along the member. These values can then be plotted on a graph to create the diagram.

3. What information can be obtained from a shear and bending moment diagram?

A shear and bending moment diagram can provide important information about the structural integrity and stability of a member, such as the maximum shear and bending forces and their locations. It can also be used to determine the size and type of reinforcement needed for the member.

4. What are some common types of loads that can affect a shear and bending moment diagram?

Some common types of loads that can affect a shear and bending moment diagram include point loads, which act at a specific point along the member, and distributed loads, which act over a certain length of the member. Other factors that can affect the diagram include the type of support at each end of the member and any applied moments.

5. How are shear and bending moment diagrams used in structural engineering?

Shear and bending moment diagrams are important tools in structural engineering for analyzing the behavior of different types of structural members and ensuring that they are strong enough to withstand the loads placed upon them. They are also used in the design process to determine the optimal size and shape of a member to meet specific structural requirements.

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