Question

Question 1 (Total 100/3 Marks) Figure 1 (all units are mm) shows a simply supported beam of span 2500 mm with a 5 kN/m load. The cross-section of the beam is a composite section made from two steel plates attached to the top and bottom of a timber section. The top steel plate is 5 mm wide and 20 mm deep. The bottom steel plate is also 5 mm wide but 10 mm deep. The timber section is 50 mm wide and 100 mm deep as shown in Figure 1. The elastic modulus of steel can be taken as 200 GPa while the elastic modulus of timber can be taken as 20 GPa. Assume both materials remain elastic under the loading a) What is the maximum bending moment in the beam? b) Transform the section and draw the transformed section. You can transform the steel to timber or timber to steel. It is your choice Calculate the centroid and the second moments of area for the transformed section. Determine the maximum stresses in the steel and timber. Draw the stress distribution through the depth of the composite beam What can you say about the strain distribution through the depth of the composite beam c) d) e) f) 5 kN/m Steel 5 mm 20 mm 50 mm 2500 mm Timber 100 mm Esteel -200 GPa Etimber 20 GPa Steel 10 mm 5 mm Not to Scale! Figure 1

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