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daphnelee-mh
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I am confused why positive value of bending moment is plotted under the axis?
Question about plotting a Bending Moment Diagram
- Engineering
- Thread starter daphnelee-mh
- Start date
In summary, a Bending Moment Diagram is a graphical representation of the variation of bending moment along a structural element. It is important to plot this diagram because it helps to visualize internal forces, identify critical points, and analyze the strength and stability of a structure. The diagram is plotted by calculating bending moment values and drawing a smooth curve. Factors such as load type, support conditions, and geometry affect the shape of the diagram. This tool is crucial in structural design as it helps determine the maximum bending moment and shear force a structure can withstand, aiding in material and dimension selection for optimal support.
I am confused why positive value of bending moment is plotted under the axis?
- #2
Lnewqban
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It is just a convention.
Please, see:
https://en.m.wikipedia.org/wiki/Bending_moment
https://en.m.wikipedia.org/wiki/Shear_and_moment_diagram
"In structural engineering and in particular concrete design the positive moment is drawn on the tension side of the member. This convention puts the positive moment below the beam described above. A convention of placing moment diagram on the tension side allows for frames to be dealt with more easily and clearly. Additionally placing the moment on the tension side of the member shows the general shape of the deformation and indicates on which side of a concrete member rebar should be placed, as concrete is weak in tension."
Please, see:
https://en.m.wikipedia.org/wiki/Bending_moment
https://en.m.wikipedia.org/wiki/Shear_and_moment_diagram
"In structural engineering and in particular concrete design the positive moment is drawn on the tension side of the member. This convention puts the positive moment below the beam described above. A convention of placing moment diagram on the tension side allows for frames to be dealt with more easily and clearly. Additionally placing the moment on the tension side of the member shows the general shape of the deformation and indicates on which side of a concrete member rebar should be placed, as concrete is weak in tension."
1. How do I plot a Bending Moment Diagram?
To plot a Bending Moment Diagram, you will need to first determine the external forces acting on the beam and their respective distances from the point of interest. Then, calculate the reactions at the supports and draw a free body diagram of the beam. Next, use the equations of static equilibrium to solve for the internal forces at the point of interest. Finally, plot the values of the bending moment on a graph, with the distance along the beam as the x-axis and the bending moment as the y-axis.
2. What is the purpose of a Bending Moment Diagram?
A Bending Moment Diagram is used to visualize the internal forces and moments acting on a beam at a specific point. It is important for understanding the structural integrity of the beam and determining if it can withstand the applied loads without failing.
3. How do I interpret a Bending Moment Diagram?
The Bending Moment Diagram shows the variation of the bending moment along the length of the beam. The positive values represent tension or bending away from the axis, while the negative values represent compression or bending towards the axis. The highest point on the diagram indicates the maximum bending moment, which is a critical point for the design of the beam.
4. What are the key factors that affect the shape of a Bending Moment Diagram?
The shape of a Bending Moment Diagram is primarily affected by the magnitude and distribution of external loads, as well as the type of support at each end of the beam. The material properties of the beam, such as its cross-sectional shape and size, also play a role in determining the shape of the diagram.
5. Can a Bending Moment Diagram be used for any type of beam?
Yes, a Bending Moment Diagram can be used for any type of beam, including simple beams, cantilever beams, and continuous beams. However, the method for calculating the internal forces and moments may vary depending on the type of beam and its support conditions.
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