$4\mathrm{.}12$ A three$-$span six$-$story reinforced concrete frame structure is depicted in the structural plan view shown in Figure $4-26($a$).$ The columns are arranged in a rectangular pattern with a spacing of $4\mathrm{.}2m.$ The simplified diagram for the lateral frame calculation is shown in Figure $4-26($b$).$ The reference wind pressure is denoted as $w_0=0\mathrm{.}55k\frac{N}{m^2},$ and the terrain category is A$.$ The along$-$wind shape factor is shown in Figure $4-26($c$).$ The height variation factor for wind pressure can be calculated using the formula

${}_z(z)=(\frac{H_{T_s}}{z_s}{)}^{2{}_s}(\frac{H_{Ta}}{z_a}{)}^{-2{}_{}}(\frac{z}{z_s}{)}^{2{}_a}$

where the subscript $"$s$"$ represents the standard terrain and the subscript $"$a$"$ represents any terrain, with $z_a=z_s=10m.$

For simplicity, the wind load can be calculated in three segments. The bottom two stories form one segment, the middle two stories form another segment, and the top two stories form the third segment. Within each segment, the wind load is considered as uniformly distributed, and the wind load value at the midpoint is taken as the average wind load value for that segment. Calculate the following:

$(1)$ Determine the along$-$wind direction wind action acting on the frame specified in the structural plan view of Figure $4-26($a$),$ and draw the simplified wind load diagram.

$(2)$ Calculate the bending moment and shear force at the bottom $($support$)$ of the frame under the action of the along$-$wind action.