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Moment area: overhang beam free-end deflection

Short answer

Applying the moment-area method, the tangent at A yields θA = 53.33/EI anticlockwise. The vertical deflection at the free end C is 506.67/EI downward.

Calculate vertical deflection at free end of the given overhanging beam using moment area method. Take EI to be constant. [Figure: beam ABC; A hinge and B roller 4 m apart; AB (2EI) carries 10 kN/m UDL; overhang BC = 2 m (EI) carries 100 kN at C.]

Given data

Overhanging beam ABC: A hinge, B roller, AB=4AB = 4 m (2EI2EI, UDL 10 kN/m), overhang BC=2BC = 2 m (EIEI) with 100 kN at C.

   10 kN/m (2EI)                100 kN
 A =============== B ------------v C
 ^       4 m       ^    2 m (EI)

Step 1: Reactions

RA=−30.00R_{A} = -30.00 kN, RB=170.00R_{B} = 170.00 kN (positive = upward; check: ∑Fy=140.00\sum F_y = 140.00 kN equals the total load 140.00 kN).

Step 2: Bending moment diagram (sagging +), as M/EIM/EI pieces

Portion (m)MM (kNm)stiffnessArea of M/EIM/EIxˉ\bar x from A (m)
0 to 4−5x2−30x- 5 x^{2} - 30 x2EI-173.332.769
4 to 6100x−600100 x - 600EI-200.004.667

(Stiffness is in terms of EIEI; "Area" is ∫M/EI dx\int M/EI\,dx in units of 1/EI1/EI; xˉ\bar x is the centroid distance from A.)

Step 3: Tangent at A

Deviation of the support at x=4x = 4 m from the tangent at A (Theorem II, moment of the M/EIM/EI area about that support):

t=(−173.33)(1.231)=−213.33EIt = (-173.33)(1.231) = \frac{-213.33}{EI}

That support does not deflect, so θA=−t/4\theta_A = -t/4:

θA=53.333EI (anticlockwise)\theta_A = \frac{53.333}{EI}\ \text{(anticlockwise)}

At C (free end) (x=6x = 6 m):

θ=θA+∑A=53.333+[(−173.33)+(−200.00)]=−320.000EI (clockwise)\theta = \theta_A + \sum A = 53.333 + [(-173.33) + (-200.00)] = \frac{-320.000}{EI}\ \text{(clockwise)} y=θA x+tP/A=320.000+[(−173.33)(3.231)+(−200.00)(1.333)]=−506.667EI (downward)y = \theta_A\,x + t_{P/A} = 320.000 + [(-173.33)(3.231) + (-200.00)(1.333)] = \frac{-506.667}{EI}\ \text{(downward)}

Answer: vertical deflection at the free end C =506.67EI= \dfrac{506.67}{EI} (kNm3^3/EI), downward.

✓ Answer checked by Claude Opus 5.5 (high effort)

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