structural / beams

Propped cantilever with a point load at any position.

Estimate the fixed reaction, prop reaction, fixed-end hogging, and sagging moment at the load for a rigidly propped cantilever.

read the result

Compatibility supplies the missing reaction.

This is a first-degree indeterminate beam. The vertical prop reaction is selected so that the prop point has zero vertical movement; the remaining vertical reaction and fixed-end action then follow from equilibrium.

Implemented equations and signs

Let L be the fixed-end-to-prop span, P the downward point load, and a its distance from the fixed end, with 0 < a < L. Taking upward reactions as positive, the prop reaction is RB = Pa2(3L - a)/(2L3) and the fixed vertical reaction is RA = P - RB. The displayed fixed-end hogging magnitude is |MA| = Pa - RBL; the sagging moment at the load is M(a) = RB(L - a).

Classic load-case variants covered

The position parameter covers a point load anywhere strictly inside the span, including the common midspan case by setting a = L/2. It also covers an off-centre point load without assuming symmetry. P = 0 is accepted as a zero-load screen. The page does not represent a prop at the fixed end or exactly at the free/prop end because the implemented compatibility case requires 0 < a < L.

Keep it as an elastic load-case screen.

  • The left support is perfectly fixed; the right support is a rigid vertical prop with no rotational restraint.
  • The load is vertical, downward, and applied at one point; signs are represented by a non-negative P input and named hogging/sagging outputs.
  • Constant EI, small deflection, zero settlement, continuous contact, and no prop flexibility or gap are assumed.
  • Shear deformation, axial force, second-order effects, member strength, connection design, and serviceability criteria are not checked.