Diagrams

Equations

1. Moment load at the free-end
Cantilever beam with moment load at the free end

\( M_A = -M \)

\( \theta_\text{max} = -\dfrac{ML}{EI} \)
\( \theta_B = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{ML^2}{2EI} \)
\( \delta_B = \delta_\text{max} \)


At any point:
\[ \theta = -\dfrac{Mx}{EI} \] \[ y = -\dfrac{Mx^2}{2EI} \]

2. Moment load on the span
Cantilever beam with moment load on the span

\( M_A = -M \)

\( \theta_\text{max} = -\dfrac{Ma}{EI} \)
\( \theta_B = \theta_C = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{Ma}{2EI} (2L - a) \)
\( \delta_B = \delta_\text{max} \)


\( 0 \le x \le a \):
\[ \theta = -\dfrac{Mx}{EI} \] \[ y = -\dfrac{Mx^2}{2EI} \]


\( a \le x \le L \):
\[ \theta = -\dfrac{Ma}{EI} \] \[ y = -\dfrac{Ma}{2EI} (2x - a) \]

3. Concentrated load at the free-end
Cantilever beam with point load at the free-end

\( R_A = P \)
\( M_A = -PL \)

\( \theta_\text{max} = -\dfrac{PL^2}{2EI} \)
\( \theta_B = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{PL^3}{3EI} \)
\( \delta_B = \delta_\text{max} \)


At any point:
\[ \theta = -\dfrac{P}{2EI} \left( 2Lx - x^2 \right) \] \[ y = -\dfrac{P}{6EI} \left( 3Lx^2 - x^3 \right) \]

4. Concentrated load on the span
Cantilever beam with point load on the span

\( R_A = P \)
\( M_A = -Pa \)

\( \theta_\text{max} = -\dfrac{Pa^2}{2EI} \)
\( \theta_B = \theta_C = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{Pa^2}{6EI} (3L - a) \)
\( \delta_B = \delta_\text{max} \)


\( 0 \le x \le a \):
\[ \theta = -\dfrac{P}{2EI} \left( 2ax - x^2 \right) \] \[ y = -\dfrac{P}{6EI} \left( 3ax^2 - x^3 \right) \]


\( a \le x \le L \):
\[ \theta = -\dfrac{Pa^2}{2EI} \] \[ y = -\dfrac{Pa^2}{6EI} \left( 3x - a \right) \]

5. Uniform load over the entire span
Cantilever beam with uniformly distributed load over the entire span

\( R_A = wL \)
\( M_A = -\dfrac{wL^2}{2} \)

\( \theta_\text{max} = -\dfrac{wL^3}{6EI} \)
\( \theta_B = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{wL^4}{8EI} \)
\( \delta_B = \delta_\text{max} \)


At any point:
\[ \theta = -\dfrac{w}{6EI} \left( x^3 - 3Lx^2 + 3L^2x \right) \] \[ y = -\dfrac{w}{24EI} \left( x^4 -4Lx^3 + 6L^2 x^2 \right) \]

6. Uniform load applied partially along the span
Cantilever beam with uniformly distributed load applied partially on the span

\( R_A = wa \)
\( M_A = -\dfrac{wa^2}{2} \)

\( \theta_\text{max} = -\dfrac{wa^3}{6EI} \)
\( \theta_B = \theta_C = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{wa^3}{24EI} (4L - a) \)
\( \delta_B = \delta_\text{max} \)


\( 0 \le x \le a \):
\[ \theta = -\dfrac{w}{6EI} \left( x^3 - 3ax^2 + 3a^2x \right) \] \[ y = -\dfrac{w}{24EI} \left( x^4 - 4ax^3 + 6a^2x^2 \right) \]


\( a \le x \le L \):
\[ \theta = -\dfrac{wa^3}{6EI} \] \[ y = -\dfrac{wa^3}{24EI} (a - 4x) \]

7. Triangular load over the entire span
Cantilever beam with uniformly varying load over the entire span

\( R_A = \dfrac{wL}{2} \)
\( M_A = -\dfrac{wL^2}{6} \)

\( \theta_\text{max} = -\dfrac{wL^3}{24EI} \)
\( \theta_B = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{wL^4}{30EI} \)
\( \delta_B = \delta_\text{max} \)


At any point:
\[ \theta = -\dfrac{w}{24EIL} \left( 4L^3x - 6L^2x^2 + 4Lx^3 - x^4 \right) \] \[ y = -\dfrac{w}{120EIL} \left( 10L^3x^2 - 10L^2x^3 + 5Lx^4 - x^5 \right) \]

8. Triangular load applied partially along the span
Cantilever beam with uniformly varying load applied partially on the span

\( R_A = \dfrac{wa}{2} \)
\( M_A = -\dfrac{wa^2}{6} \)

\( \theta_\text{max} = -\dfrac{wa^3}{24EI} \)
\( \theta_B = \theta_C = \theta_\text{max} \)

\( \delta_\text{max} = -\dfrac{wa^3}{120EI} (5L - a) \)
\( \delta_B = \delta_\text{max} \)


\( 0 \le x \le a \):
\[ \theta = -\dfrac{w}{24EIa} \left( 4a^3x - 6a^2x^2 + 4ax^3 - x^4 \right) \] \[ y = -\dfrac{w}{120EIa} \left( 10a^3x^2 - 10L^2x^3 + 5ax^4 - x^5 \right) \]


\( a \le x \le L \):
\[ \theta = -\dfrac{wa^3}{24EI} \] \[ y = -\dfrac{wa^3}{120EI} (a - 5x) \]


Table 1.1: Equations according to degree \( n \) of \( M/EI \) Diagram

  • Degree of \( M / EI \), \( n \)
  • Maximum rotation \( EI \ \theta = \dfrac{M_R \ L}{n + 1} \)
  • Moment reaction, \( M_R \)
  • Maximum deflection, \( EI \ \delta = \dfrac{M_R \ L^2}{n + 2} \)

Case

\( n \)

\( M_R \)

\( EI \ \theta \)

\( EI ~ \delta \)

1. Moment Load
Cantilever beam with moment load at the free-end
\( 0 \) \( M \) \( \dfrac{M_R \ L}{1} \) \( \dfrac{M_R \ L^2}{2} \)
2. Concentrated Load
Cantilever beam with point load at the free-end
\( 1 \) \( PL \) \( \dfrac{M_R \ L}{2} \) \( \dfrac{M_R \ L^2}{3} \)
3. Uniform Load
Cantilever beam carrying a distributed load
\( 2 \) \( \dfrac{w \ L^2}{2} \) \( \dfrac{M_R \ L}{3} \) \( \dfrac{M_R \ L^2}{4} \)
4. Triangular Load
Cantilever beam with triangular load
\( 3 \) \( \dfrac{w \ L^2}{6} \) \( \dfrac{M_R \ L}{4} \) \( \dfrac{M_R \ L^2}{5} \)