For a fixed beam with a concentrated load w at \(\frac{1}{4}\) of
A. <span class="math-tex">\(\frac{{16{M_p}}}{{3L}}\)</span>
B. <span class="math-tex">\(\frac{{4{M_p}}}{L}\)</span>
C. <span class="math-tex">\(\frac{{32{M_p}}}{{3L}}\)</span>
D. <span class="math-tex">\(\frac{{6{M_p}}}{L}\)</span>
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Right Answer is: C
SOLUTION
Given:
Fixed beam with concentrated load L/4 from one end
Calculation:
Number of Plastic hinges = Ds + 1 = (4 - 2) + 1 = 3
i.e. at A, B and C
From geometry,
\(\Delta = \frac{L}{4}{\theta _A}\) and \({\theta _A} = 3{\theta _B}\)
According to virtual work principle,
External work done = Internal work Done
\(W\Delta = {M_P}{\theta _A} + {M_P}{\theta _A} + {M_P}{\theta _B} + {M_P}{\theta _B}\)
\(W\frac{L}{4}{\theta _A} = 2{M_P}{\theta _A} + \frac{{2{M_P}{\theta _A}}}{3}\)
\(\Rightarrow W = \frac{{32}}{3}\frac{{{M_P}}}{L}\)