Flow Influence Line Method In The Small&Middle Span Bridges Design Flow Of Jiangxi Province

The water hazard of bridge brings enormous damage to bridge and brings huge economic loss to the country. Especially for the Jiangxi province in frequent flooding area, the damage caused by the water hazard of bridge were more serious. Therefore, how to effectively determine bridge design flow in Jiangxi province, how to make simply and effectively assessment for small&middle span bridges of the Jiangxi province’s flood-fighting ability. This has the vital significance for the Jiangxi province.Now the calculation of design flow mainly includes two kinds of methods: observation data calculation method, no observation data calculation method. And no observation data calculation method widely used in most regions of China use the rainfall to calculate runoff.Combined with the geology hydrological conditions in Jiangxi province, Jiangxi province mainly uses the region-al empirical method, instantaneous unit hydrograph method. These methods need catchment area, basin grandient and other lots of factors, which lead to data collection difficulties.that collected much error, etc.Based on professor Wen Yusong’s team put forward the flow influence line method combined with the Jiangxi province’s instantaneous unit hydrograph method, This paper using VB program draw the conversion rainfall map of load which relatived to the design frequency of Jiangxi province is1/100、1/50、1/25. Aslo this paper use the conversion rainfall load series of Jiangxi province loaded in the flow influence line which has be made to get maximum flood peak discharge relatived to the design frequency.This paper contrasts bridge case of Jiangxi province which has be analysed by the flow influence line method and bridge case of Jiangxi province which has be analysed by the method recommended by the Jiangxi province rainstorm hydrological manual. The flow influence line method has certain precision because of the error in5%-10%. This shows that flow influence line method can widely use to most of small&middle span bridges of Jiangxi province which have rainfall data. The flow influence line method must be widely used in jiangxi province because the flow influence line method has characteristics that require less factor、Get the data simply and has results in high precision.