Max Bending Moment of Rigidly Clamped Beam

AI Thread Summary
The discussion revolves around calculating the maximum bending moment for a rigidly clamped beam with a central point load. The poster, Eddie, is confused about the derivation of the maximum bending moment formula, specifically the term involving "8." He correctly identifies the vertical reactions at the ends as F/2 but struggles with the moment calculation. A key point raised is the contradiction in considering the maximum bending moment as a function of x, as it should be a fixed value. The conversation seeks clarification on the derivation of the maximum bending moment formula used in engineering texts.
eddie135
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Dear Experts,

I am a gradute engineer posting here for the first time. I have a query regarding the simple problem to which i cannot seem to get the correct Max bending moment. Here is the problem.

A beam of length L rigidly clamped at both ends with a point load F in the centre, i.e, at location l/2
I calculate the vertical reactions to be f/2 on each end.
Now if we take a section through the beam at a distance x from the left hand side and summing moments about this section, i get the following

M(x) = F(x - L/2) + M + R1x

where R1 is the left hand vertical force which is equal to f/2 and M which is the fixing moment due to LHS of beam being rigidly clamped. From here I get lost. The Max bending moment from various books for this scenario is given to be

Mmax = Fx/2 - FL/8

I am baffled as to where the 8 comes from.

I would really appreciated it if anyone can shed some light on how this max moment is derived.

Looking forward to hearing from you.

Best Regards
Eddie
 
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How can the maximum bending moment be a function of x, if the moment is maximized with respect to x?
 
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