Solving Shear and Bending Moment for a Beam

In summary, the conversation discusses how to draw the shear and bending moment diagrams for a beam and loading. The beam is 1.4m long and has various loads at different points. The conversation also mentions that the bending moment should be the same regardless of which side it is taken from, but the values obtained are conflicting. After discussing the issue, it is determined that the reaction forces were incorrect and need to be reworked in order to obtain the correct values.
  • #1
NBAJam100
146
0

Homework Statement



For the beam and loading, draw the shear and bending moment diagrams. Find the max and min abs vals of shear and bending moment.
+= pointing upwards, - = pointing downwards
The beam is 1.4m long.
Load A = -.54kN at x=0,
Load B= pin support at x=.2m (Found to be +1.8kN)
load C= -1.35kN, x= .7m
load D= roller support at x= 1.1m (Found to be .63kN)
load E= -.54 kN at x= 1.4m

The Attempt at a Solution



Im shooting myself in the foot over this because its so simple and I've reworked it about 500 times and keep getting conflicting answers... The bending moment should be the same for the same point regardless of what side i take it from, but i keep getting different values...
going from left end of beam, fixing right side.
From 0<x<.2 --> B.M = -540*x
From .2<x<.7 --> B.M = -540*x + 1800*(x-.2)

Now go from right side, fixing left end.

From 0<x<.3 --> B.M = -(540)*x
From .3<x<.7 --> B.M = -540*x + 630*(x-.3)

I am getting conflicting values for x=.7m for my bending moment... what am i doing wrong, someone please help before i go crazy...
 
Last edited:
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  • #2
NBAJam100: Your reaction forces are incorrect. You forgot to check equilibrium to ensure your reactions are correct. First, rework the problem to obtain the correct reaction forces. Then everything should work out fine.
 
  • #3
ahhh wow, i totally looked right past that. bleh, thanks a lot nvm.
 

FAQ: Solving Shear and Bending Moment for a Beam

1. What is shear and bending moment in a beam?

Shear and bending moment are two important forces that act on a beam when it is subjected to external loads. Shear is a force that causes one part of the beam to slide against the other part, while bending moment is a force that causes the beam to bend or twist.

2. How do you solve for shear and bending moment in a beam?

To solve for shear and bending moment in a beam, you need to first determine the external loads acting on the beam, such as point loads, distributed loads, or moments. Then, you can use equations derived from equilibrium and shear and moment diagrams to calculate the shear and bending moment at any point along the beam.

3. Why is it important to solve for shear and bending moment in a beam?

Understanding the shear and bending moment in a beam is crucial for designing and analyzing structures. This information helps engineers determine the strength and stability of beams, and ensure that they can withstand the expected loads without failing.

4. What are some common methods for solving shear and bending moment in a beam?

The two most common methods for solving shear and bending moment in a beam are the method of sections and the method of joints. The method of sections involves cutting the beam at a specific point and analyzing the forces on the resulting free body diagram, while the method of joints involves analyzing the forces at the joints of the beam.

5. Can software be used to solve for shear and bending moment in a beam?

Yes, there are many software programs available that can quickly and accurately solve for shear and bending moment in a beam. These programs use advanced algorithms and equations to analyze the beam and provide detailed results, making the process more efficient and less prone to errors.

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