Exact Analysis of Indeterminate Structures: Displacement Methods - Examples

The problems use one consistent local sign convention per example. When using a table or simulator, first match its moment and rotation signs before transferring numerical values.

Example 1: Rotational Stiffness with Far End Fixed

A prismatic member has EI=24000 kN⋅m2EI=24000\text{ kN}\cdot\text{m}^2 and L=6.0 mL=6.0\text{ m}. Find the near-end rotational stiffness when the far end is fixed.

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Example 2: Rotational Stiffness with Far End Hinged

Use the same member data as Example 1, but the far end is an ideal hinge. Find KK.

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Example 3: Distribution Factors at a Joint

Three members meeting at joint JJ have rotational stiffnesses K1=12K_1=12, K2=18K_2=18, and K3=30K_3=30 in consistent units. Find their distribution factors.

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Example 4: Distributing an Unbalanced Joint Moment

At a joint, the algebraic unbalanced moment is +50 kN⋅m+50\text{ kN}\cdot\text{m}. The connected members have distribution factors 0.200.20, 0.300.30, and 0.500.50. Find the balancing corrections.

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Example 5: Carry-Over to a Fixed Far End

A moment-distribution correction of −24 kN⋅m-24\text{ kN}\cdot\text{m} is applied at the near end of a prismatic member whose far end is fixed. Find the classical carry-over correction.

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Example 6: Fixed-End Moment Magnitude for a Uniform Load

A prismatic fixed-fixed beam has w=18 kN/mw=18\text{ kN/m} and L=5.0 mL=5.0\text{ m}. Find the magnitude of each fixed-end moment.

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Example 7: Slope-Deflection with One Joint Rotation

Member ABAB has EI/L=5000 kN⋅m/radEI/L=5000\text{ kN}\cdot\text{m/rad}, no member load, no chord rotation, θA=0\theta_A=0, and θB=0.002 rad\theta_B=0.002\text{ rad}. Find MABM_{AB} using the lesson equation.

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Example 8: Companion End Moment

Using the same member and rotations as Example 7, find MBAM_{BA}.

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Example 9: Chord Rotation from Joint Translation

A frame column has length L=4.0 mL=4.0\text{ m}. Its top joint translates 12 mm12\text{ mm} to the right relative to its base. Under the small-angle approximation, find the chord-rotation magnitude.

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Example 10: Non-Sway or Sway Classification

A rectangular frame has fixed bases and is subjected only to symmetric vertical loading. Geometry and stiffness are symmetric about the centerline. Should a lateral sway degree of freedom be expected in the symmetric idealization?

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Example 11: Moment-Distribution Convergence Check

After several distribution cycles, the largest remaining joint correction is 0.08 kN⋅m0.08\text{ kN}\cdot\text{m} while final member moments are about 120 kN⋅m120\text{ kN}\cdot\text{m}. Compute the correction as a percentage of that moment scale.

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