Question 9.74: Determine the location of the shear center O of a thin-walle...

Determine the location of the shear center O of a thin-walled beam of uniform thickness having the cross section shown in Figures P9.74.

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Section Properties: 

\begin{aligned}d A &=t d s=t r d \theta \quad y=r \sin \theta \\d I &=y^{2} d A=r^{2} \sin ^{2} \theta(t r d \theta)=r^{3} t \sin ^{2} \theta d \theta \\I &=r^{3} t \int_{0}^{2 \pi} \sin ^{2} \theta d \theta \\&=r^{3} t \int_{0}^{2 \pi}\left(\frac{1-\cos 2 \theta}{2}\right) d \theta \\&=\pi r^{3} t \\d Q &=y d A=r \sin \theta(t r d \theta)=r^{2} t \sin \theta d \theta \\Q &=r^{2} t \int_{0}^{\theta} \sin \theta d \theta=r^{2} t(1-\cos \theta)\end{aligned}

 

Shear Flow Resultant: 

\begin{aligned}q &=\frac{V Q}{I}=\frac{V r^{2} t(1-\cos \theta)}{\pi r^{3} t}=\frac{V}{\pi r}(1-\cos \theta) \\F &=\int q d s \\&=\int_{0}^{2 \pi} \frac{V}{\pi r}(1-\cos \theta) r d \theta \\&=\frac{V}{\pi} \int_{0}^{2 \pi}(1-\cos \theta) d \theta=2 V\end{aligned}

Shear Center: Sum moments about the center of the split tube to find

\begin{aligned}&V e=F r \\&e=\frac{F r}{V}=\frac{2 V r}{V}=2 r\end{aligned}

 

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