Solving Stresses in Beams: Reactions at B & F

In summary, the conversation discusses the determination of reactions at B and F for a supported beam with an L-shaped beam connected to it. The user provides an attempt at solving for the reactions using the sum of forces and moments equations. The calculated reactions are R_B = 1848.03 lb and R_F = 26.97 lb. The user also asks for assistance in determining the shearing forces around the L-shaped beam and the bending moment and force at point D.
  • #1
luciriv
5
1
Homework Statement
Figure shows a supported beam, where a=2 and b=3, and the cross section is a rectangle with the sides a=2 in and b=3 in. Determine the support reactions, maximum normal and shearing stresses. Draw the shearing force and bending moment diagrams.
Relevant Equations
In the figure, pulg means inches. The shearing stress is $$\tau = \dfrac{VQ}{Ib},$$ where ##V## represents the shearing force, ##Q## is the first moment of area, ##I## is the moment of inertia of the entire cross section, and ##b## is the width of the beam at the position where ##\tau## acts.
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To determine the reactions at B and F, I don't know how to handle that L-shaped beam connected to the horizontal beam. My attempt is:
$$\sum F_{y} \colon\;\;\; -200 + R_{B} - 75 + 32 + R_{F} - 1632 = 0$$
from which it follows that ##R_{B} + R_{F} = 1875##.
$$\sum M_{B} \colon\;\;\; -5 \times 200 - 8 \times 75 + 25 \times 32 + 33R_{F} - 90 = 0.$$
So ##R_{F} = 26.97\, lb## and ##R_{B} = 1848.03\, lb##.
Is this right? Any hint or help to determine the shearing forces around that L-shaped beam is welcome.
 
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  • #2
That L shape will impose a punctual moment and a shearing force at point D of the main beam.
 
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  • #3
luciriv said:
Homework Statement:: Figure shows a supported beam, where a=2 and b=3, and the cross section is a rectangle with the sides a=2 in and b=3 in. Determine the support reactions, maximum normal and shearing stresses. Draw the shearing force and bending moment diagrams.
Relevant Equations:: In the figure, pulg means inches. The shearing stress is $$\tau = \dfrac{VQ}{Ib},$$ where ##V## represents the shearing force, ##Q## is the first moment of area, ##I## is the moment of inertia of the entire cross section, and ##b## is the width of the beam at the position where ##\tau## acts.

View attachment 286775

To determine the reactions at B and F, I don't know how to handle that L-shaped beam connected to the horizontal beam. My attempt is:
$$\sum F_{y} \colon\;\;\; -200 + R_{B} - 75 + 32 + R_{F} - 1632 = 0$$
from which it follows that ##R_{B} + R_{F} = 1875##.
$$\sum M_{B} \colon\;\;\; -5 \times 200 - 8 \times 75 + 25 \times 32 + 33R_{F} - 90 = 0.$$
So ##R_{F} = 26.97\, lb## and ##R_{B} = 1848.03\, lb##.
Is this right? Any hint or help to determine the shearing forces around that L-shaped beam is welcome.
what is your assessment of the bending moment and force at point D are for the L-shaped beam?
 
  • #4
For finding end reactions, your treatment of the force at E in determining its moment about B is good. But you have signage errors in determining the sum of moments and you missed some loads and I don't know what is the 90.
 

1. What are the different types of reactions at point B and F in a beam?

The different types of reactions at point B and F in a beam are support reactions, which include fixed support, roller support, and pinned support.

2. How do you determine the magnitude and direction of reactions at point B and F?

The magnitude and direction of reactions at point B and F can be determined by using the equations of equilibrium, which state that the sum of all forces and moments acting on a body must equal zero.

3. What is the difference between statically determinate and indeterminate beams?

A statically determinate beam is one in which the reactions can be determined using only the equations of equilibrium, while an indeterminate beam requires additional equations or methods to determine the reactions.

4. Can you solve for reactions at B and F using the method of joints?

Yes, the method of joints can be used to solve for reactions at B and F. This method involves analyzing the forces acting on each joint of the beam and using the equations of equilibrium to solve for the reactions.

5. How do you account for distributed loads when solving for reactions at B and F?

Distributed loads can be accounted for by converting them into equivalent point loads at the centroid of the distributed load. The equivalent point load can then be treated as a regular point load when solving for reactions at B and F.

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