A simply supported pedestrian bridge is to be constructed in a city park and two designs have been proposed as shown in case a and case b. The truss members are to be made from timber. The deck consists of 1.5-m-long planks that have a mass of 20 kg/m². A local code states the live load on the deck is required to be 5 kPa with an impact factor of 0.2. Consider the deck to be simply supported on stringers. Floor beams then transmit the load to the bottom joints of the truss. (See Fig. 6–23.) In each case find the member subjected to the largest tension and largest compression load and suggest why you would choose one design over the other. Neglect the weights of the truss members.

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1.25 m H B G C F case a D -1.25 m 1.25 m-1.25 m-1.25 m E