(Solved): 4. The two-span highway bridge shown in Figure Q4. a is a steel and concrete ...

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4. The two-span highway bridge shown in Figure Q4. a is a steel and concrete composite multi-girder construction. The concrete deck is \( 250 \mathrm{~mm} \) thick (assume this thickness is uniform across the bridge), with concrete grade C40/50 and the steel is \( \mathrm{S} 355 \mathrm{~J} 2 \mathrm{G} 3 \). (a) At the preliminary design stage, use an appropriate span to construction depth ratio to determine the steel girder depth. [3 marks] (b) Determine the effective lengths Lei, Leii, Leii as defined in Figure Q4.b. [3 marks] Question 4 continues on the following page Question 4 continued (c) A cross section of the bridge is shown in Figure Q4.a. Assuming that there are 4 rows of shear connectors for the top flange, spaced across a width of \( 300 \mathrm{~mm} \), find the effective width of the internal girders over the regions \( L e_{i,} L_{e_{i j}} \) and \( L e_{\text {iil. }} \). [6 marks] for the internal girders in Lei. Use the following sectional dimensions for the steel girder: - Top flange: \( 400 \mathrm{~mm} \times 30 \mathrm{~mm} \) - Bottom flange: \( 440 \mathrm{~mm} \times 40 \mathrm{~mm} \) - Web: \( 1330 \mathrm{~mm} \times 12 \mathrm{~mm} \). The height of web is the clear distance between top and bottom flanges. [14 marks]