Fiqure $12.$A

$12\mathrm{.}6$ The shed in Figure $12.$ A has double $26$ knee braces on each column to resist the lateral force. Lumber is Redwood $($open grain$).$ The braces are to be connected to the columns with $16$d common nails. Lateral seismic force to roof diaphragm is $w_{EL}=66l\frac{b}{f}t.$ Heights: $h_1=12ft,h_2=4ft.$ Use LRFD procedures and remember to use the appropriate LRFD load factor for seismic forces.

Find: $,a.$ The required number of nails for the brace connection, assuming that $C_M=1\mathrm{.}0.$

b$.$ The required number of nails for the brace connection, assuming that the connection is exposed to the weather.

c$.$ How would a and $b$ change if helically threaded hardened$-$steel nails with $D=0\mathrm{.}148in.$ and $l=3\mathrm{.}5in.$ were used?