Truss Design –Case Study Due: 11/03/2016 The configuration of a truss can have a significant effect in that compression members must be “beefed up” due to buckling. Members that are always in tension can be quite slender, even to the point of being rods or cables. For this assignment, let’s compare two classic truss designs: the Pratt truss and the Howe truss, as shown below. For this assignment, assume that, for dead load, P = 15 kips and, for live load, P = 100 kips. Also, assume that the members are to be made of steel with a yield stress of 45 ksi. For compression members, use a critical stress value of 24 ksi. Compute the following for each truss: a. Structural Analysis of each truss using RISA 2D. Include the following output in your submittal: Axial force diagram, diagram showing the reactions and member forces, and the deflected shape of each truss. Use ASCE LRFD load combinations for the analysis. b. The LRFD axial force demand. Do not include the truss’s self-weight in these calculations. c. The required cross sectional area for each member. Assume a minimum value of 1 in2. d. Tabulate your results. Showing member forces, cross sectional areas, member length, and member weight (the density of steel is 490 lb/ft3). Compute the total weight of each truss. Which truss has the most efficient configuration? What other conclusions do you draw?