Recall the definition of Q.
Q is the first
moment of the area between the location where the shear stress
is being
calculated and where the shear stress is zero.
where A’
is the area between the location where the shear stress is zero and
the location
where the shear stress is being calculated and y_{bar} is the distance from the neutral axis to
the centroidal axis of A’.
Key points in the calculation of Q are that you must identify the location in
the x-section
where the shear stress is zero. Also
note that for symmetric x-sections, the shear stress distribution must also be
symmetric. Further note that the maximum shear stress occurs
at the neutral axis. Consider the cases
shown below where z is the neutral axis.
Click
here for four other cases.
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