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Tony's Intertwingled Memex • Reference Manual

Beam Deflection and Shearing Force (Civil Engineering)

Formulas & Definitions

A civil structural engineer is evaluating the internal forces on a 12 m12\text{ m}12 m highway bridge girder supporting a non-uniform traffic load. The internal bending moment distribution M(x)M(x)M(x) along the span of the beam (measured in kN⋅m\text{kN}\cdot\text{m}kN⋅m for x∈[0,12]x \in [0, 12]x∈[0,12]) is modeled by:

M(x)=48x−16x+4−2x2M(x) = 48x - \frac{16}{\sqrt{x + 4}} - 2x^2M(x)=48x−x+4​16​−2x2

In structural mechanics, the internal shear force V(x)V(x)V(x) (measured in kN\text{kN}kN) is the spatial rate of change of the bending moment:

V(x)=dMdxV(x) = \frac{dM}{dx}V(x)=dxdM​

  1. Pre-process the radical denominator term in M(x)M(x)M(x) using negative and rational exponent laws.
  2. Differentiate M(x)M(x)M(x) to find the analytical expression for the internal shear force V(x)V(x)V(x).
  3. Post-process your derivative into standard radical notation, and evaluate the internal shear force at the support coordinate x=0 mx = 0\text{ m}x=0 m and at the mid-span x=5 mx = 5\text{ m}x=5 m.