Solve part b please Consider the two$-$bay, three$-$story, $RC$ frame shown below. It is to be designed to carry gravity loads. The columns have a $16"$x$18"$ cross$-$section and the beams have a $16"$x$24"$ cross$-$section. The beams carry a total dead load of $900lb\frac{s}{f}t($including its own weight$)$ and a live load of $1,200$ lbs$/$ft$.$ The modulus of elasticity of the concrete is the same for the whole frame. You may assume that the dead load has a load factor of $1\mathrm{.}2$ and the live load has a load factor of $1\mathrm{.}6.$

$($a$)$ Determine the maximum positive moment and the maximum negative moments that may develop in the beams in the second level of the frame by an elastic analysis. Different possible live$-$load distributions as recommended in ACI $318$ should be considered to obtain the maximum moment values. Use a simplified frame model consisting of only the second level of the frame and the columns above and below with their far ends fixed for the analysis, as permitted by ACI $318.$ Also, the sideway of the frame under the gravity loads can be ignored. The lengths of the columns and beams are measured between the points where the dashed centroidal lines are connected. To account for the effect of member cracking, use the effective moment of inertia recommended in ACI Table $6\mathrm{.}6\mathrm{.}3\mathrm{.}1\mathrm{.}1($a$)$ in Lecture $21$ Notes. The values of the maximum negative moments in the beams should be calculated at the face of the columns. You may use either the moment$-$distribution or the matrix analysis method to do the analysis.

$($b$)$ Use ACI moment coefficients to determine the maximum positive and negative moments in the beams in the second level. Compare your results with those from part $($a$).$