Study on the collapse of the steel bridge due to flooding in Baringin Village of Padang City, Indonesia

Abstract

Baringin Bridge is a steel bridge that connects between Baringin Village and Koto Lalang Village in Padang City, Indonesia. Baringin Bridge was made of steel frame construction using the Box Caisson type foundation, with 7.6 meters width and 60 meters length. This bridge was built with a semi cantilever method with temporary support using coconut tree trunks. The construction of Baringin Bridge was terminated due to flood in Baringin River on November 2, 2018, which causes the collapse of the temporary scaffolding. The flood made the bridge move away about 300 meters from its foundation. This study aims to find out the cause of the steel bridge collapse. The assessment was carried out to analyze the existing bridge construction, the cause of flooding, and flood discharging that occurred on November 2, 2018. The calculation of forces acting on the scaffold when the bridge collapsed was also conducted. The results of the study show that Baringin River discharge on November 2, 2018, was 407.17 m³/s with a river flow velocity of 1.45 m/s. The calculation results of the scaffold show that the bridge should be able to withstand forces arising from the weight of the steel frame and the flow of the river. However, the collision of the wood logs that hit the scaffold’s feet causes the collapse of the steel bridge.