The load capacity of the historical Pratt truss shown in the photo is to be investigated when the load on the bottom girder AB is 600 lb/ft. A drawing of the bridge shows the centerline dimensions of the members. All the members are bolted to gusset plates. The vertical and half-diagonal members each have a cross sectional area of 3.60 in², and each of the main diagonal members and the top cord have a cross-sectional area of 5.80 in². The side girder has a cross sectional area of 13.2 in² and a moment of inertia of 350 in⁴. Establish a structural model of the bridge truss and justify any assumptions you have made. Perform a computer analysis to determine the force in each member of the truss. From the results, draw the moment diagram for the side girder. Check your results by using the method of sections to determine the force in some of the truss members. Neglect the weight of the members and take E = 29(10³) ksi.

Transcribed Image Text:

15 ft 15 ft A 15 ft 15 ft 15 ft 15 ft 15 ft 15 ft Prob. 17-4P B Food