Solving Stresses in Beams: Reactions at B & F

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SUMMARY

The discussion focuses on calculating the reactions at supports B and F for an L-shaped beam connected to a horizontal beam. The user applied static equilibrium equations, resulting in the equations RB + RF = 1875 lb and RF = 26.97 lb, leading to RB = 1848.03 lb. However, the user received feedback indicating potential errors in moment calculations and signage, particularly regarding the forces acting at point D and the significance of the value 90 in the moment equation.

PREREQUISITES
  • Understanding of static equilibrium principles in mechanics
  • Knowledge of shear and bending moment diagrams
  • Familiarity with the shearing stress formula: τ = VQ/Ib
  • Ability to calculate moments about a point in a beam
NEXT STEPS
  • Review the principles of static equilibrium in beam analysis
  • Learn how to construct shear force and bending moment diagrams
  • Study the calculation of moments and forces at various points in a beam
  • Explore the implications of different loading conditions on beam reactions
USEFUL FOR

Engineering students, structural analysts, and professionals involved in beam design and analysis will benefit from this discussion, particularly those focusing on static equilibrium and shear force calculations.

luciriv
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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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That L shape will impose a punctual moment and a shearing force at point D of the main beam.
 
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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?
 
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.
 

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