Deflection of Beams — Worked Examples

Unless stated otherwise, the examples assume small deflections, linear elasticity, and constant flexural rigidity EIEI.

1. Simply Supported Beam with a Central Point Load

A simply supported beam has L=6.0 mL=6.0\text{ m}, P=20 kNP=20\text{ kN} at midspan, E=200 GPaE=200\text{ GPa}, and I=120×106 mm4I=120\times10^6\text{ mm}^4. Determine the maximum deflection.

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2. Simply Supported Beam with Full-Span UDL

A simply supported beam has L=5.0 mL=5.0\text{ m}, w=8.0 kN/mw=8.0\text{ kN/m}, E=200 GPaE=200\text{ GPa}, and I=100×106 mm4I=100\times10^6\text{ mm}^4. Determine the maximum deflection.

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3. Cantilever with a Free-End Point Load

A cantilever has L=3.0 mL=3.0\text{ m}, P=10 kNP=10\text{ kN}, E=200 GPaE=200\text{ GPa}, and I=60×106 mm4I=60\times10^6\text{ mm}^4. Determine free-end deflection magnitude.

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4. Cantilever with Full-Span UDL

Use the same cantilever stiffness as Example 3, but apply w=4.0 kN/mw=4.0\text{ kN/m} over the full 3.0 m3.0\text{ m} span. Determine free-end deflection magnitude.

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5. Superposition of a Midspan Point Load and UDL

A 5.0 m5.0\text{ m} simply supported beam has E=200 GPaE=200\text{ GPa} and I=100×106 mm4I=100\times10^6\text{ mm}^4. It carries a central 10 kN10\text{ kN} point load and a full-span UDL of 4.0 kN/m4.0\text{ kN/m}. Determine midspan deflection.

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6. Double Integration for a Cantilever End Load

A cantilever of length LL is fixed at x=0x=0 and carries a downward point load PP at x=Lx=L. Derive its free-end deflection.

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7. Moment-Area Solution for the Same Cantilever

Use the moment-area method for a cantilever with end load PP and length LL. Determine the free-end slope magnitude and tangential deviation.

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8. Effect of Doubling Moment of Inertia

A beam remains in the same linear-elastic load case, but its moment of inertia is doubled while EE, load, and span are unchanged. Determine the deflection ratio.

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9. Span Sensitivity for a Central Point Load

A simply supported beam with a central point load has fixed PP, EE, and II. The span doubles. How does maximum deflection change?

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10. Choosing a Method for Standard Load Cases

A simply supported beam carries a central point load and a full-span UDL. Verified standard elastic formulas are available for both, and only the maximum midspan deflection is required. Which method is most efficient?

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11. Symmetry Check on Beam Slope

A simply supported beam and loading are perfectly symmetric about midspan. What is the slope at the center of the span?

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