STEP $1$: INFLUENCE LINES

Problem Statement: You will need to understand the behavior of each truss to safely define the

appropriate member sizes. For Option $1$ and Option $2,$ construct the influence diagrams for the

reaction forces at the supports and the force in each of the members. Assume that each truss is subject

to vertical loading, directed downward along the horizontal chord from joint A to joint E$.$ Use positive

values to designate tension member forces and negative values for compression.

The influence diagrams for the members on the right side of each truss will be mirror images of those

on the left because of symmetry. Therefore, for Option $1,$ construct the influence lines for the

following nine members: AB$,$ BC$,$ AF$,$ BF$,$ BG$,$ CG$,$ CH$,$ FG$,$ and GH$.$ And for Option $2,$ construct

the influence lines for the following eight members: AB$,$ BC$,$ AF$,$ BF$,$ BG$,$ CG$,$ FG$,$ and GH$.$

Be sure to keep the results for Option $1$ separate from those for Option $2.$ Each design option

must be investigated independently.

STEP $2$: DESIGN FORCE CALCULATIONS

Problem Statement: For Option $1$ and Option $2,$ use the two sets of influence diagrams from Step $1$

to calculate the design force in each member. For Option $1,$ calculate the design forces for the

following nine members: AB$,$ BC$,$ AF$,$ BF$,$ BG$,$ CG$,$ CH$,$ FG$,$ and GH$.$ For Option $2,$ calculate the

design forces for the following eight members: AB$,$ BC$,$ AF$,$ BF$,$ BG$,$ CG$,$ FG$,$ and GH$.$

The design force for a member is the maximum tension and$/$or compression force due to applied

loads. Consider live load acting in combination with dead load. Note that some members may have

two design forces: one is maximum tension, and the other is maximum compression. For these cases,

do not simply focus on the maximum absolute value; both values must be retained to determine the

proper member size.

Use the following load values for your calculations:

$1.$ Total dead load $=150$ lbs$/$ft $($this includes the self$-$weight of the truss$)$

$2.$ Pedestrian live load $=300$ lbs$/$ft

$3.$ Maintenance vehicle live load $=5000$ lbs$.$