- 2077 Chaitra · 7 marks
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, , with 50 kN horizontal (to the right) at 2 m above the base. Beam BC: 6 m, , UDL 20 kN/m (down). Right column CD: 3 m, , 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 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 and (moments are taken on the free-end side).
| Member | EI | (kNm) | ||
|---|---|---|---|---|
| DC | 0-3 | |||
| CB | 0-6 | 3 | ||
| BA (top 2 m) | 0-2 | |||
| BA (lower 2 m) | 2-4 |
The column is split at the 50 kN load, where the expression for changes.
Integrals
| Member | divide by | contribution | |
|---|---|---|---|
| DC | 270 | 270.00 | |
| CB | 3780 | 2520.00 | |
| BA (0-2) | 1700 | 850.00 | |
| BA (2-4) | -13.33 | -6.67 | |
| Total | 3633.33 |
Answer: horizontal deflection of the free end (kNm/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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