The Performance Assessment And Remedial Measures Of Bridge Structure

The bridge is an infrastructure which built across the river also used to pass safely from onernside of the road to another to cross the river; on the road shall be kept strong to serve intendedrnpurposes. The bridge structure requires detail, assessment before and after construction bothrndue to possible failures. Many countries have come upon different mitigation measure tornovercome failure by providing bridge assessment. Ethiopian Road Authority follows up bridgernstructure failure by recording all necessary data about bridge and Road situation. rnThe Bilate River Bridge is the one among those encountered local abutment failure.rn The abutment failure of the bridge was seen at different times, which is observed in the fieldrnassessment. The analysis was conducted on the abutment scour failure for a different returnrnperiod of time. The existing bridge opening size was the 26m length, 5m wide. Both sides ofrnriverbank material were taken and analysis is done in a laboratory result express that particlerndiameter of 1.5mm and 34.5mm for D50 and D95 respectively.rnThe maximum design flood estimation resulted in 284.2mrn3rn/s, and 327.3 mrn3rn/ at the Bilate River rnfor 50-year and 100-year return period respectively. In the design flood estimation rainfallrunoffrnmodelrnanalyzedrnbyrnInitialrnandrnconstantrnlossrnmethodrnandrndirectrnrunoffrnbyrnthernSCSrnunitrnrnhydrographrnmethodrnalsornbasernflowrnbyrnrecessionrnmethod.rnrnThernBridgerninstabilityrnevaluatedrnbyrnHECrnRASrn5.0.1;rnhasrnbeenrnpreparedrnbyrntakingrninputsrnlike;rnrnriverrncrossrnsection,rndesignrnflood,rnandrnriverbankrnmaterials.rnrnrnThernlocal abutmentrnscouringrnobservedrninrnthernvicinityrnofrnthernstructurernof thernbridgernincorporaternrnwithrnovertoppingrnwhichrnenduresrnBridge tornfail.rnrnrnThernmodelrnresultsrnshowrnthatrndominaterncausernofrnabutmentrnscoursrnofrnthernbridgernwasrnanrninadequaternrnopeningrnsizerntornpassrndesignrnfloodrnatrnthernbridge;rnbecausernofrnconstrictionrnatrnthernbridgernwithinrnthernrnriverrnrnhas resulted in an increase the flow velocity so that, the abutment has been scoured.rnCountermeasures were reviewed based on the hydraulic analysis result calculated. Based onrnhydraulic analysis results; the recommended river training work and increase the opening sizernof a bridge across the river.

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