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Title: Assessment of Failure on Drainage Structures along the Ethiopian National Railway line of Sebeta-Mieso (Case study of Akaki River crossing drainage structure)
???metadata.dc.contributor.*???: Dereje Hailu (PhD)
Yerosan, Abera
Keywords: Hydrologic models- HEC-HMS;HEC-RAS;Akaki New Railway Bridge;Objective function;Calibration;validation;Simulation
Issue Date: Nov-2015
Publisher: AAU
Abstract: A railway drainage system gives vital role for effective, efficient operation of rail track. This study worked on an assessment of railway drainage system problem along the Addis AbabaMieso railway line, specifically on Akaki rives crossing. It was done to check adequacy of hydraulic structure provided on Akaki River crossing by undertaking hydrologic and hydraulic analysis. Hydrologic modeling of the Akaki catchment area was developed by HEC-GeoHMS program with the help of Arc-GIS and hydrologic analysis was computed by HEC-HMS program. The catchment land use, soil type, rainfall data, Akaki river stream flow data, etc were used to develop hydrological model. SCS unit hydrograph and flood frequency analysis methods were used to estimate instantaneous peak design discharge for 50 and 100 year return period. Model input parameters were calibrated and verified with observed flow data of the river at Akaki gauging station. Design discharge computed in this case for 50/100 year return period was 743.2m3/s and 834.5m 3 /s respectively at bridge location from catchment area of 894km 2, where these values were used to check adequacy of the bridge. Hydraulic models were developed to determine water-surface profiles along the stream reaches for the discharges established in the hydrologic analyses The HEC-RAS step-backwater hydraulic analysis model was used to determine water-surface profiles for the bridge. Crosssectional elevation data, hydraulic-structure geometries, roughness coefficients along with peakdischarge estimated were used as input for the model. Based on available data’s water surface profile for peak discharge was determined by the program. Finally adequacy of the bridge was evaluated for both peak discharges. Although the site of the bridge was fixed based on geometrical alignment of railway, the output of HEC-RAS analysis confirmed that Akaki Railway Bridge has sufficient size to safely convey both peak design flow during the design period. Thus, it is Akaki Railway Bridge was hydraulically efficient over its design period.
Appears in Collections:Railway Engineering

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