Bridge Collapse in Nigeria: A Case Study of Tatabu Bridge in Mokwa Local Government Area of Niger State

Abstract

Large parts of Niger State are located in low terrain and have proximity to River Niger: the largest river in Nigeria; coupled with the presence of three hydro Electric power stations in the state. Niger State has been confronted annually by flood disaster that has destroyed many lives and properties. The focus of this paper is to investigate the causes behind Tatabu bridge collapse. In this investigation, soil strength and index test, hydrological data, nature of the terrain, concrete strength test and evaluation of flood impact on the bridge and its embankments using ANSYS Finite Element Method were conducted. The results of the investigations revealed that the collapsed bridge was positioned within a valley as well as steady increase in precipitation from 2015 to 2017 which directly increased the stream flow rate and also runoff.  It was also observed that the debris settlement within the cell of the collapsed bridge contributed to reduction of the cross sectional area of single cell. The compressive strength test of the bridge members revealed that the strength are within acceptable limit. The authors recommended that there is the need for embankment protection either covers vegetation, stone pitch, slope stabilizer, or concrete interlocking is required for future consideration. Due to increase in water balance, the new bridge capacity should be increased to accommodate the high volume of water.  The new bridge should be reconstructed above the valley or repositioned away from the valley. it is also recommended that a complete replacement of the underlain material forming the adjacent slope to the bridge retain wall with a better compacted engineering soil to avoid future pavement failure of the kind.

Keywords: Bridge, Flood, ANSYS, Collapse, Terrain