The inspected structure is located in Athens/Greece adopting the engineering genius of Architect Santiago Calatrava who designed this impressive footbridge, commonly known as “HARP BRIDGE”. The shape of the bridge looks like a harp inspired by the ancient Greek monuments and sculptures of the Classical Era.
The bridge is made of steel and is formed by a main curved pillar of 50m high, from which 14 high strength steel wire cables hang down to sustain the 94m walkway of about 6m width, suspended over the road traffic area.
What makes this bridge one of its kind is the arrangement of the cable-stay back span. In an asymmetric cable-stay bridge, where the main span is longer than the back-span, the back-span cables are generally anchored to the ground to provide the necessary stability. In most such bridges, the back-span cables are angled so that they provide a horizontal force, helping the bridge’s mast to resist the horizontal pull from the main-span cables. On Harp Bridge, the back-span cables are vertical, resisting none of the sideways pull from the main span. Instead, that pull is absorbed through the curvature of the pylon, as a compressive thrust.
The decking is formed by short timber planks, lined up neatly in the longitudinal direction. These are supported on steel ribs and the whole deck is cross-braced to provide the necessary stiffness. It makes crossing a busy traffic junction looks better and certainly is considered among the modern landmarks of the city of Athens.
HiSCS Engineers performed the inspection of this iconic bridge using a 3D laser scanning device to record the sagging of the stay cables as well as any abnormal condition such as inclination and/or tilting of the structural elements in comparison with the as-built data.
A drone has been used to get a close access to the pilar, the cable anchorages and the steel deck elements recording the current condition without annoying traffic and pedestrians. An evaluation report including bridge health index analysis and the necessary proposals for future maintenance and repair works has been delivered to the Owner, the Urban Rail Transport Operator Company of Athens.
