Moment Distribution Method — Worked Problems

Fixed-End Moments — Uniformly Loaded Restrained Span

A prismatic beam ABAB is fixed against rotation at both ends, has L=6L=6 m and a downward uniformly distributed load w=12w=12 kN/m. Find the clockwise-positive member-end fixed-end moments. Uniform load and two fixed beam endsw = 12 kN/mAB6 m

Step-by-Step Solution

0 of 3 Steps Completed
1

Fixed-End Moments — Central Point Load

A prismatic fixed–fixed beam of length 8 m carries a downward central load of 64 kN. Find the two FEMs. Central concentrated load on fixed spanP = 64 kN4 m + 4 m

Step-by-Step Solution

0 of 3 Steps Completed
1

Rotational Stiffness — Fixed versus Hinged Far End

A beam member has constant EI=24,000EI=24{,}000 kN·m2^2 and L=5L=5 m. Compute near-end rotational stiffness for (a) a fixed far end and (b) a hinged far end.

Step-by-Step Solution

0 of 3 Steps Completed
1

Distribution Factors — Three Members at One Joint

Three non-translating members meet at a free-to-rotate rigid joint JJ with near-end stiffnesses 88, 1212 and 2020 MN·m/rad. The algebraic unbalanced moment is U=+40U=+40 kN·m. Calculate the correcting increments.

Step-by-Step Solution

0 of 3 Steps Completed
1

Pinned Far-End Release — Uniform-Load FEM Adjustment

Beam BCBC carries w=12w=12 kN/m over L=6L=6 m. Its near end BB is rotationally connected to a rigid joint; physical end CC is a hinge. Find load-only moments before releasing BB. Pin-released far end for moment distribution12 kN/m; L = 6 m

Step-by-Step Solution

0 of 3 Steps Completed
1

One-Joint Distribution — Fixed A, Continuous B, Hinged C

A continuous two-span beam has AB=5AB=5 m under w=10w=10 kN/m and BC=6BC=6 m under w=12w=12 kN/m. AA is fixed, BB rotationally continuous, and CC a hinge/roller. EIEI is the same. Find all four final member-end moments. Two-span beam for one-joint balance10 kN/m12 kN/mABC5 m6 m

Step-by-Step Solution

0 of 5 Steps Completed
1

One-Joint Distribution — Both Exterior Ends Fixed

Use the previous spans, loads and constant EIEI, but now both AA and CC are fixed against rotation. Find four member-end moments from one release of B. Two-span beam with both remote ends fixed10 kN/m12 kN/mABC

Step-by-Step Solution

0 of 5 Steps Completed
1

Two-Joint Iteration — Three Equal Spans with Central UDL

A continuous beam ABCDABCD has three 4-m spans with identical EIEI; AA and DD are fixed, BB and CC are rotationally continuous. Only middle span BCBC carries w=12w=12 kN/m. Compute representative distribution cycles and final end moments. Three-span beam for alternating B and C moment distributionw = 12 kN/mABCD4 m4 m4 m

Step-by-Step Solution

0 of 5 Steps Completed
1

Sway Translation — Fully Restrained Column Magnitudes

A 4-m prismatic column with EI=10,000EI=10{,}000 kN·m2^2 has both end rotations restrained and a prescribed lateral relative translation Δ=0.010\Delta=0.010 m. Find the magnitudes of column end sway moments and shear. Do not treat this as a free-rotation frame result.

Step-by-Step Solution

0 of 4 Steps Completed
1

Convergence Decision — Residual Moments and Precision

A moment-distribution cycle leaves residual joint moments UB=−0.08U_B=-0.08 kN·m and UC=+0.12U_C=+0.12 kN·m. The stated absolute joint-equilibrium tolerance is 0.10 kN·m. Decide whether another cycle is needed.

Step-by-Step Solution

0 of 3 Steps Completed
1