THE CHIRAJARA BRIDGE COLLAPSE
The Chirajara Bridge was part of the Bogotá–Villavicencio highway project in Colombia, designed to improve connectivity between the capital and the eastern plains.
It was conceived as a major engineering landmark: a long-span, cable-stayed structure crossing a deep ravine in a seismically active region.
The bridge was built to shorten journey times, improve transport links and support traffic between Bogotá and the Llanos region.
CONSTRUCTION INFORMATION
Construction began as part of the Fourth Generation road infrastructure programme, which aimed to modernise Colombia’s transport network.
The Chirajara Bridge consisted of two independent carriageways, each supported by its own set of cable stays anchored to tall concrete pylons.
Its form followed a common modern design strategy for deep valleys, where cable-stayed systems provide an economical way of achieving long spans with minimal foundations in difficult terrain.
Cable Stays
Cable stay bridges are advantageous because they can span long distances and use fewer supports. They also make construction easier as the pylons can be built first with the deck put in later.
This arrangement also allows the bridge to be constructed in stages, with the pylons erected first and the deck sections added progressively from each side. The design was selected because it was well suited to the mountainous site constraints, reduced the need for supports below the bridge and offered an efficient method of construction.
January 2018
However, the project became internationally known after the dramatic collapse of one of its pylons on 15 January 2018, during construction. At the time of failure, the deck had not yet been fully connected, and only a portion of the structure was complete.
The collapse resulted in the tragic loss of nine workers and drew significant attention to construction practices, design verification processes and structural safety in large infrastructure projects.
Project background
Subsequent investigations revealed that the failure stemmed from a design error involving the lower section of the tower, specifically the transverse (horizontal) ties connecting the legs of the pylon.
The design did not provide adequate capacity to resist the combination of axial, bending and shear forces induced during construction.
Cracking had already been observed in the week leading up to the collapse, but its significance was not fully recognised.
FAILURE
When one of the transverse diaphragms failed, the load was rapidly redistributed to adjacent members, which were also under-designed. This triggered a progressive collapse mechanism, ultimately causing the entire pylon to buckle and fall.
Independent engineering assessments concluded that the failure was not due to material defects, construction errors, or seismic activity, but rather to insufficient structural detailing and inadequate redundancy in the tower design.
PEER REVIEW
The collapse highlighted the importance of robust peer review, especially for complex, non-standard structures in challenging environments.
As a result of the findings, the partially standing opposite tower was demolished as a precaution. PHOTO As a result of the findings, the partially standing opposite tower was demolished as a precaution. PHOTO As a result of the findings, the partially standing opposite tower was demolished as a precaution. PHOTO
REDESIGN
A redesign was commissioned, led by a different engineering team, opting for a new viaduct structure rather than trying to replicate the original cable-stayed concept.
The redesigned bridge incorporated greater redundancy, improved detailing, and a more conservative approach to force distribution and seismic resilience.
The Chirajara Bridge collapse has since become a frequently cited case study in structural engineering.
It illustrates several critical lessons: the need for rigorous independent checking, the sensitivity of cable-stayed bridges during staged construction, and the risks associated with complex structures that lack redundancy.
It also demonstrates the importance of recognising and acting upon early warning signs, such as cracking or unusual structural movement.
Cable Stayxs
Cable stay bridges are advantageous because they can span long distances and use fewer supports. They also make construction easier as the pylons can be built first with the deck put in later.
This arrangement also allows the bridge to be constructed in stages, with the pylons erected first and the deck sections added progressively from each side. The design was selected because it was well suited to the mountainous site constraints, reduced the need for supports below the bridge and offered an efficient method of construction.
Collapse sequence
The collapse occurred while the bridge remained under construction. One of the bridge pylons failed together with its adjoining section of deck.
The incident resulted in fatalities and led to a detailed investigation of the design, construction sequence and structural behaviour.
“The failure highlighted the importance of examining the complete structural load path."
DESIGN ASPECTS
The deck was a 13m wide, composite steel-concrete structure with two 1.5m deep steel longitudinal girders and 0.84m deep steel transverse beams supporting a 0.2m thick reinforced concrete slab every 3m. Each tower had a hollow 38m tall mast to anchor the cables. The mast had a rectangular section and was supported by a structure with a diamond-shape elevation; the widest part of the diamond accommodated the roadway. The specified compressive strength for the tower concrete was 35MPa. Standard cylinder test reports provided to the supervision company show results exceeding the specified strength. Columns supporting the mast were 6 by 1.6m in cross section (solid), with the longer side oriented axially with the deck. The lower part of the tower included a 500mm thick wall acting as a web between the columns. The standard to be met by the deformed reinforcing bars was not specified in the design drawings provided to the authors.
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ot doneProject background
The Chirajara Bridge formed part of a wider highway improvement scheme connecting Bogotá with Villavicencio and the Llanos region.
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