+3 votes
in Mathematics by kratos

Find the value of X and draw the bending moment diagram for the beam shown below. Given that RA = 1000 N & RB = 4000 N,

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+3 votes
by kratos
 
Best answer

For finding the Value of X, For that first draw the FBD, Taking moment about point A UDL = 2000 X 2 = 4000 acting at a distance of (X + 1) from point A.

MA = 4000 ⋅ (X + 1) - RB ⋅ (2 + X) + 1000 ⋅ (X + 3) = 0

4000 + 4000X - 8000 - 4000X - 1000X -3000 = 0

1000X = 1000 X = 1m

Calculation for Banding Moment diagram

Here total three-section line, which cut AC, CB and BD

Distance of section 1-1 from point A is X1

Distance of section 2-2 from point A is X2

Distance of section 3-3 from point A is X3

Consider left portion of the beam

Consider section 1-1, taking moment about section 1-1

BM1-1 = 1000.X1

It is Equation of straight line (Y = mX + C), inclined linear

Inclined linear means value of bending moment at both nearest point of the section is varies with X1 = 0 to X1 = 1

At X1 = 0 BMA = 0 ...(8)

At X1 = 1 BMC = 1000 ...(9)

i.e. inclined line 0 to 1000 (Inclined line)

Consider section 2-2, taking moment about section 2-2

BM2-2 = 1000.X2 -2000(X2-1)

It is Equation of parabola (Y = mX2 + C),

Parabola means value of bending moment at both nearest point of the section is varies with X2 = 1 to X2 = 3 and make a curve.

At X2 = 1 BMC = 1000 ...(8)

At X2 = 3 BMB = –1000 ...(9)

i.e. Curve between 1000 to -1000

Consider section 3-3, taking moment about section 3-3

BM3-3 = 1000.X3 –4000(X3 – 2) + 4000(X3 – 3)

It is Equation of straight line (Y = mX + C), inclined linear

Inclined linear means value of bending moment at both nearest point of the section is varies with X3 = 3 to X3 = 4

At X3 = 3 BMB = –1000 ...(8)

At X3 = 4 BMB = 0 ...(9)

i.e. Curve between -1000 to 0

Plot the BMD with the help of above value, BMD is show in fig,

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