Chirajara Bridge
Chirajara Bridge
Viaducto Chirajara
Guayabetal, Cundinamarca, Colombia
492 feet high / 150 meters high
630 foot span / 192 meter span
2023
Chirajara Bridge is the highest bridge in Colombia with a deck 150 meters above a forested creek that flows into the great Rio Negro River gorge along the Bogota-Villavicencio highway. Originally to be a cable stayed bridge, the final design is a cantilevered concrete beam bridge with a total length of 460 meters with a span configuration of 114.6 +192 +114.6 meters on piers 73 and 54 meters tall.
The new beam design came after a V-shaped cable stayed configuration was scrapped as the replacement for the original diamond shaped cable stayed tower that collapsed in 2018. This accident forever tarnished the once perfect track record of zero cable stayed bridge collapses stretching back more then 60 years to the first modern cable stayed span from 1957.
On January 15, 2018, the entire west side of the nearly finished Chirajara Bridge collapsed into the gorge killing 10 construction workers. After an investigation, engineers discovered that the horizontal connection within the diamond-shaped towers was insufficiently designed with a minimal number of prestressing cables. Incorrect calculations were also made about the lateral strength of the concrete diaphragm wall that connected the lower V-shaped legs of the towers. The study of the bridge collapse is detailed in an excellent IABSE paper written by Dr. Christos T. Georgakis, Dr. Yozo Fujino, Siegfried Hopf, Klaus H. Ostenfeld and Dr. S. Eilif Svensson.
Normally the cross tie beams in a concrete cable stayed bridge tower are at least 2 meters thick with several rows of prestressing cables. For the Chirajara Bridge the cross tie was just .6 meters thick with only one row of 12 prestressing cables holding the two sides of the tower together.
Although many of the world's cable stayed bridges have giant concrete wall "diaphragms" below the cross tie, rarely are they used to restrain the lateral tension of the tower legs. The Chirajara Bridge engineer assigned #4 rebar stirrups vertically every 20 cm within the diaphragm which was not nearly strong enough to counter the load path change between the upper A-shape columns of the tower and the lower V-shape columns that focus the weight of the bridge down into the narrow foundation pad.
The older Chirajara Beam Bridge from 1995 still carries eastbound traffic and crosses 90 meters over Chirajara creek.
Completed in 2002, the 122 meter high Pipiral Bridge is the second highest span along the Bogota-Villavicencio route and is located about 10 kilometers to the east of Chirajara.
Sadly the Chirajara Bridge disaster would not be the last cable stayed accident in 2018 as on August 14 a tower and span of the Morandi cable stayed bridge in Genoa, Italy collapsed from excessive corrosion of the wire stays.
New Chirajara Bridge render.
V-shaped cable stayed design that was to replace the collapsed bridge.
Original Chirajara Bridge render with the diamond shaped towers.
Old Chirajara Bridge under construction in 2018.
The IABSE report stated that the diaphragm, between the pylon knees, was a 0.6m thick link slab, extending the entire 6m width of the pylon legs along the bridge axis. The link slab was post-tensioned in both longitudinal (along bridge axis) and transverse (knee to knee) 2 directions. 14 tendons each consisting of 8strands 0.6"in diameter (nom.A =140 mm), were provided in the longitudinal direction of the bridge. 12 tendons each consisting of a single 0.6" strand were provided as ties between the knees of the pylon in transverse direction and anchored within the pylon legs.
Horizontal reinforcement in the link slab was provided at the top and bottom faces by N°4 (⌀12.7mm) bars per 250mm in both longitudinal and transverse directions. The reinforcement ended at the edge of the link slab. No reinforcement, other than the 12 single strands, was provided between the link slab and the pylon legs.
Implosion of East Tower of Chirajara Bridge on July 11, 2018.
Early construction view before the collapse.
Chirajara Bridge satellite image.
Chirajara Bridge location map.
MORANDI BRIDGE COLLAPSE
On August 14, 2018 one of the three towers and two of the spans of Italy's Morandi Bridge collapsed in the city of Genoa. Years of corrosion from salty ocean air and factory pollution caused the steel tendons in one of the large concrete stays to snap. Unlike most cable stayed bridges that have several stays, the Morandi Bridge had only one set per span so there was no redundancy. The cantilevered design did not allow for the towers to support the weight of just one opposing span without bending or overturning.
Image by Luca Zennaro.
Image by AFP.