ARCE $226-$Structural Systems

$2.$ The roof of the $12-$node model you built for Homework $2$ is stabilized with $4$ braces as discussed in class and as shown in the figure below. The roof is shown in the $x-y$ plane, as a stable plane truss. The reactions and zero force members are to be determined in class as part of Student Worksheet #$4.$

a$.$ Use Method of Joints to calculate forces in all bars. Show if these forces are tension $($T$)$ or compression $($C$).$ Mark the force magnitudes on each bar in the figure below: compression forces in red, tension forces in blue and zero forces in black.

b$.$ Work on your $12-$node model: $(1)$ add four braces to the roof, as shown in the figure below; and $(2)$ add three braces to the vertical walls. The three braces added to the walls must correspond to the supports at A and $D$ shown in the roof diagram: pin at A and roller at D$.$ Take a clear picture of your model and include it in your HW$3$ submission file. The photo must clearly show all added bars and the names of the students.