Rust damage may have caused Nanfang’ao Bridge collapse (Taiwan)
An investigation into the collapse of the Nanfang’ao Bridge in Yilan County, near Taipei City last year has identified corrosion in several of the bridge’s steel cables. The Taiwan Transportation Safety Board (TTSB) announced the initial results of its investigation into the facts of the case, but did not conclusively state what caused the collapse. Investigations to see how other road construction projects and overloading affected the bridge are also still being conducted and a comprehensive report is scheduled to be released in August.
According to the TTSB report, surveillance footage showed abnormal movement in one of the bridge’s arches before the collapse, which dislodged the casings on five of the bridge’s 13 cables. The western end of the bridge then dropped by eight degrees, causing the deck of the bridge to fracture, the report said.
TTSB investigators found deficiencies in several of the bridge’s suspenders, including rust damage and steel strands which had “escaped” from their anchors on the bridge’s arches and deck. However, because of the bridge’s design features, safety inspectors would not have been able to see the rust damage with the naked eye, and failed to establish additional inspection standards taking this into account, said Wang Hsing-chung (王興中), a senior TTSB investigator.
Yilan County Government inspected the bridge a total of seven times from 2001-2016. On April 28, 2016, responsibility for the bridge was transferred to the Maritime and Port Bureau, and no further inspections were conducted, the report said.
Three fishing boats were crushed when the 140-meter suspension bridge in Taiwan’s northeastern Su’ao Township collapsed on October 1st 2019, resulting in the deaths of six crew members.