Real Life Parabola's - Comparing the Sydney Harbour Bridge a

Students get an opportunity to investigate the difference in the curves of 2 Bridges that are similar - The Sydney Harbour Bridge and the Tyne Bridge in Newcastle.
Can you find the equations of the curves for each of the bridges? What is similar about the 2 bridges? What is different between the 2 bridges? Why is the curve of the 2 Bridges different?