Solving Shear and Bending Moment for a Beam

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SUMMARY

The discussion focuses on calculating shear and bending moment diagrams for a 1.4m beam subjected to various loads. The loads include a downward force of -0.54kN at x=0, a pin support of +1.8kN at x=0.2m, a downward force of -1.35kN at x=0.7m, a roller support of +0.63kN at x=1.1m, and another downward force of -0.54kN at x=1.4m. The user encountered conflicting bending moment values due to incorrect reaction forces, which were identified and corrected by another forum member, emphasizing the importance of checking equilibrium in structural analysis.

PREREQUISITES
  • Understanding of beam loading and support types
  • Knowledge of shear and bending moment diagrams
  • Familiarity with equilibrium equations in static systems
  • Basic proficiency in structural analysis techniques
NEXT STEPS
  • Review the principles of static equilibrium in structural analysis
  • Study how to construct shear and bending moment diagrams for various loading conditions
  • Learn about different types of beam supports and their effects on reaction forces
  • Practice solving problems involving multiple loads and supports on beams
USEFUL FOR

Engineering students, structural analysts, and professionals involved in civil engineering who are focused on understanding beam behavior under various loading conditions.

NBAJam100
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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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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.
 
ahhh wow, i totally looked right past that. bleh, thanks a lot nvm.
 

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