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Frame horizontal deflection at free end

Short answer

The horizontal deflection at the free end equals 3633.3/EI (kN·m³) towards the left, obtained by integrating M·m/EI along the three cantilever members for the given loading.

Determine the horizontal deflection at free end using method of virtual work. [Figure: frame fixed at the bottom of the left column (2EI, 4 m high, 50 kN horizontal load at mid-height, 2 m above the base); top beam of 6 m (3 m + 3 m, 1.5EI) with 20 kN/m UDL; right column EI, 3 m high, hanging down to a free end where a 30 kN horizontal load acts.]

Given data

Frame fixed at the base A (0,0). Left column AB: 4 m high, 2EI2EI, with 50 kN horizontal (to the right) at 2 m above the base. Beam BC: 6 m, 1.5EI1.5EI, UDL 20 kN/m (down). Right column CD: 3 m, EIEI, hanging down from C to the free end D, where a 30 kN horizontal load acts towards the left. Required: horizontal deflection at the free end D by virtual work.

    B =========== C        UDL 20 kN/m on BC
    |             |
 50->| (2 m)      | 3 m
    |             D <- 30 kN (free end)
    A (fixed)

Virtual load

Apply a unit horizontal load at D, to the left (the same direction as the 30 kN). Distances ss are measured from D along DC, from C along CB, and from B along BA. Since the structure is a cantilever fixed at A, no reactions are needed to find MM and mm (moments are taken on the free-end side).

MemberssEIMM (kNm)mm
DC0-3EIEI30s30sss
CB0-61.5EI1.5EI90+10s290 + 10s^23
BA (top 2 m)0-22EI2EI450−30s450 - 30s3−s3 - s
BA (lower 2 m)2-42EI2EI350+20s350 + 20s3−s3 - s

The column is split at the 50 kN load, where the expression for MM changes.

Integrals

Member∫Mm ds\int Mm\,dsdivide bycontribution
DC270EIEI270.00
CB37801.5EI1.5EI2520.00
BA (0-2)17002EI2EI850.00
BA (2-4)-13.332EI2EI-6.67
Total3633.33
ΔDh=3633.33EI\Delta_{Dh} = \frac{3633.33}{EI}

Answer: horizontal deflection of the free end =3633.3/EI= 3633.3/EI (kNm3^3/EI), towards the left (the direction of the unit load and the 30 kN force). Assumed: the 50 kN load acts to the right and the 30 kN load to the left.

✓ Answer checked by Claude Opus 5.5 (high effort)

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