Answer
$15.6\times10^{4}N$
Work Step by Step
Let's apply the equation $F=Shear\space stress\times area$ for a rivet to find the force experienced by each rivet,
$F=(5\times10^{8}\space Pa)\pi (5\times10^{-3}m)^{2}\approx3.9\times10^{4}N$
The maximum tension that can be applied to each beam (T) = $4F=4\times3.9\times10^{4}N$
$T=15.6\times10^{4}N$
