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Frame AFD, SFD, BMD (60 kNm, 50 kN)

Short answer

Reactions: Ha=0, Va=43.64 kN↑, Ve=36.36 kN↑. AB: N=-30.86, V=30.86, M linear 0→87.27 kN·m. At B a 60 kN·m couple jumps moment to 147.27 kN·m (right face) on BC. CD: V linear -6.36→-36.36, M parabolic max 128.18 bottom at C. DE: N=-36.36, V=0, M=0.

Draw axial force, shear force and bending moment diagrams for the frame given in figure below. [Figure: inclined member A-B-C rising from a hinged support at A to C (A to B horizontal projection 2 m, B to C 3 m); a 50 kN force and a 60 kNm couple at B; horizontal member C-D of 6 m carrying 5 kN/m UDL; right column D-E of height 4 m with E on a roller support.]

Assumptions (taken from the figure):

  • A(0,0) hinged; inclined member A–B–C at 45°: B = (2,2), C = (5,5); 50 kN downward and 60 kN·m clockwise couple at B.
  • Beam C–D = 6 m with 5 kN/m downward; column D–E = 4 m with E on a roller (vertical reaction only).

Sign convention: N is positive in tension; V is positive when the forces on the part before the section (travelling A → end) point along the left-hand normal of the member axis (upward on a left-to-right beam); M is quoted as a magnitude with the tension face named. Support reactions are drawn on the free-body of the whole frame.

                   /C------------------------D
                  /                          |
               ///                           |
              /                              |
           ///                               |
          /                                  |
       /B/                                   |
      /                                      |
   ///                                       E
  /
A/

Support reactions

Equilibrium of the whole frame gives ΣFx=0\Sigma F_x = 0, ΣFy=0\Sigma F_y = 0 and ΣM=0\Sigma M = 0.

  • HAH_A = 0.00 kN →
  • VAV_A = 43.64 kN ↑
  • VEV_E = 36.36 kN ↑

Check: the three equilibrium equations of the complete frame (and the hinge condition, where present) are satisfied to rounding (residuals below 10−910^{-9}).

Axial force, shear force and bending moment at the key sections

SectionN (kN)V (kN)M (kN·m)
AB at A-30.8630.860.00
AB at B-30.8630.8687.27 (right face)
BC at B4.50-4.50147.27 (right face)
BC at C4.50-4.50128.18 (right face)
CD at C0.00-6.36128.18 (bottom)
CD at D0.00-36.360.00
DE at D-36.360.000.00
DE at E-36.360.000.00

Shape of the diagrams

  • AB: V constant (steps at point loads), M linear
  • BC: V constant (steps at point loads), M linear
  • CD: V linear, M parabolic
  • DE: V constant (steps at point loads), M linear
  • AFD: constant between loads on a member, changing only where a load component acts along the member.
  • BMD is drawn on the tension side of each member; it is continuous at rigid joints (moment is transferred) and zero at hinges and at free ends.

Salient features

  • Maximum bending moment = 147.27 kN·m at B, tension on the right face

✓ Answer checked by Claude Opus 5.5 (high effort)

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