Problem $4$: Approximate method for Frames

$(25$ points$)$

A highway overpass is supported by a two$-$bay rigid frame. In order to perform the preliminary design of the members and foundation, we want to perform an approximate analysis. The foundations are idealized as fixed. Now a team member has calculated the earthquake loading as an equivalent static load as shown in the figure below.

Part $1)$ List the assumptions you make in order to perform an approximate analysis of the frame. $(5$ pts$).$

Part $2)$ Use the approximate analysis to determine the moment at point D$.(10$ pts$)$

Part $3)$ Use the approximate analysis to find the reactions at point A$.(10$ pts$)$