Collapse of the Chirajara Cable-Stayed Bridge in Colombia

The Chirajara Bridge is part of a highway project located about 40 mi to the southeast of Bogota, Colombia. The collapsed structure was a cable-stayed bridge consisting of two diamond-shaped towers, with a main span length of 940 ft and two side spans of 262 ft. On January 15, 2018, while under construction and with only 164 ft of the floor system remaining to be constructed between the towers, the western tower suddenly collapsed, destroying that part of the bridge. The other tower remained standing, approximately in the same construction stage as the collapsed tower. Modjeski and Masters was engaged one week after the collapse to conduct a forensic investigation that included: an in situ inspection of the collapsed structure, analytical studies, an evaluation of the design, a review of the construction documentation, and testing of materials from critical structural components. Global analyses were performed to determine the loading effects in the bridge before collapse, and refined nonlinear analyses were conducted to estimate the capacity of the tower and to identify the failure mode. The investigation was concluded 4 months after the collapse and, based on the resulting data, the cause of the collapse was determined to be a deficiency in the strength of the tower. The design erroneously assumed that the reinforcing along most of the height of the diaphragm between the lower legs of the tower was effective to resist the horizontal tensile force caused by the tower’s geometry, as opposed to typical practice which utilizes a tension tie at the change in direction of the tower legs.