Comparing cable-supported to archstructures footbridges across historic sites

Three arch-type as well as 3 cable supported alternatives have been developed for footbridges above historic sites. The two categories of arches and cable supported structures exhibit a completely different behaviour, since the latter are more flexible. The first cable variant is a straight intersection of variable width. In comparison with an arch, it is striking that the deformability is much greater the fundamental frequencies being significantly lower. However, the characteristic values for dynamics, such as the Scruton number and the accelerations of the bridge deck are significantly better. To span the site of 200 m in length, pylons of 46.7 m in height are needed. As a second alternative, a semi-circular suspension footbridge of variable height has been developed. Direct comparison with an arch counterpart is not evident. However, it could be deduced that this structure has a fairly high frequency and is also not sensitive to the important types of vibration. A full elevated walkway around a circular site can certainly be compared to its arch-shaped counterpart. Despite the lower fundamental frequency, the higher flexibility and the increased consumption of steel, the cable-supported structure performs better as for its dynamic behaviour.