Analyze and compare two trusses, arched configurations of the Pratt Truss and the Howe Truss in Figures P4.56 (a) and (b), respectively. The trusses have the same depth, length, panel spacing, loading, and supports. All joints are pinned. For each truss, do the following. a) Compute all bar forces and indicate tension or compression for each force. b) Determine the required cross-sectional areas for each bar, given an allowable tensile stress of 45 ksi, and an allowable compressive stress of 24 ksi. Note that the allowable compressive stress is lower due to buckling. c) Tabulate your results showing bar forces, cross sectional areas, and lengths. d) Calculate the total weight of each truss and determine which truss has a more efficient configuration. Explain your results. e) What other conclusions can you draw from the study?

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100 kips 100 kips 100 kips 100 kips 100 kips 6 @ 15' 90' (a) 100 kips 100 kips 100 kips 100 kips 100 kips 6 @ 15' 90' (b) 10' 10' 17' 17' 20' 20'