Question

Designing a truss bridge This lab involves the design of a truss bridge, which is a Pratt truss and should be designed to handle the loads shown in Fig- ure l (1 kip = 1000 lb). Note that the loads are the same on each of the two trusses for the bridge, so what is in Figure 1 is only half the loading on the bridge. Your job is to develop an optimal design for the bridge, Figure 1. Schematic of the Pratt truss bridge. both as a function of (0) the angle of the bridge, as well as due to (ii) choice of materials (steel or wood) considering their initial cost and transportation costs. J α=tan-10h10) 5 kips 10 kips 10kps 10 kips 10 kips 10 kips 10 ft 10 ft 10 ft 10 ft 10 ft 10 ft Problem information Considering the loading on the bridge, develop a technical report that conveys the following I. 2. 3. Loading on each member (in kips) as a function of the truss angle, α Loading state of each member (compression or tension) The optimal angle, α, to the nearest 5° for both a steel and wooden truss bridge, considering the total amount of material necessary to complete the bridge (if there are any zero force members, design them as if they have the force of the weakest other member in the truss) 4. Cost of the steel and wooden bridge as a function of a, considering only the initial material cost 5. Cost of the steel and wooden bridge as a function of a, considering the initial material cost (which 6. Recommendation of final design: material choice, optimal a, forces, sizes, state, total cost (which includes the cradle-to-gate embodied energy includes the cradle-to-gate embodied energy) and the transportation cost to site Here are the required materials for each element of the problem: (1) and (2) requires a hand-calculation solution, using for example the method of joints. You should solve this on engineering paper and turn it in with your typed report (3) requires using the forces in each member as a function of α in a calculation in which you vary α by 5° (from 5° to 85°) and solve for forces in each member, whether in compression or tension, and the area required by each member (considering allowed design stresses). Then you can solve for the volume of each member, and sum them together for a total volume required .(4) and (5) requires you to use the calculation from (3), but compute associated costs (3), (4), and (5), should have graphs of each y-axis variable as a function of α .(6) The final recommendation must be presented clearly and all in one place Problem givens FS-2 UTS( steel, compression)-29000 psi; UTS(wood, compression)-7000 psi; UTS( steel, tension)-29000 psi; UTS(wood, tension)-6000 psi: FS-2 Wt. density (steel)- 500 lb/f; Wt. density (wood)-50 lb/ft Initial cost (steel) $1.00/lb; Initial cost (wood) $1.001b Transportation cost (both)-$05/1b/mile: Steel is 20 mi and wood 100 mi from site . . .

Answer 1

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