Needing a linking road across a busy interchange, the local government of Envigado, just south of Medellin, decided to build a symbolic bridge. The bridge is considered as a representative of the effort and commitment of a community to overcome the turbulent situation in the country at the time. The explicit wish to overcome difficulties has been captured in this bridge whose cost and style can only be understood by considering the circumstances. A structure of big dimensions, albeit rational and plain, has been designed. Since its completion in 2004, this landmark bridge has been nationally awarded by two institutions in recognition of its innovative iconic character for the community and aesthetic merit.
The bridge has two cable-stayed spans of 121 m and 60 m, respectively; and three 20.2 m long access spans. The 18.6 m wide deck has a straight alignment in the longer cable-stayed span and a curved transition in the remaining spans. It has a cross section with high torsional inertia consisting of a tri-cellular concrete box girder with 2.4 m overhangs, which is both longitudinally and transversally post-tensioned. The deck is suspended from stays every 10 to 12 m.
The stay cables, which are arranged in a central layout, stretch as continuous members through a steel saddle at the top of the tower, where they all converge. It is one of the few bridges with this cable-stay arrangement. The north abutment serves as anchorage for several of the backstays. The central pylon is made of reinforced concrete and has a rectangular cross-section of variable width in both directions. It is 50 m high and is inclined 5° to achieve a more dynamic visual experience and landmark character, which makes it stand out in the cityscape.
Because the labour cost was relatively low in Colombia, the design of the various structural elements of the bridge was aimed to optimize material use, requiring a more complex implementation and more personnel on site. The choice of this particular stay arrangement allowed to reduce the dimensions of the pylon as well as the number of stay anchors. The design was carried out in accordance with the specifications of the Colombian Standard which is similar in many respects to AASTHO. The bridge site belongs to a medium grade seismic zone hence the bridge was calculated for a spectrum with a maximum acceleration of 5 m/s2.
Sobrino, Juan A.; Urban cable-stayed bridge in Envigado (Colombia), presented at FIB Symposium 2004, 26-28 April 2004, Avignon.