流量影响线及其在桥梁山洪水害预报中的应用

在单位线法的基础上提出流量影响线法。流量影响线的数学模型与简支梁应力影响线的数学模型相同,这样就将洪峰流量计算转换成结构力学中的影响线最不利加载。流量影响线法需要利用历史上的洪水在桥梁墩台上留下水痕高程并收集到降雨量系列,完成流量影响线的标定。在接收到新的降雨量数据后,将雨量当作移动荷载在流量影响线上加载,计算出流量历程曲线,据此确定出最大洪峰流量和到达桥址处的时间即造峰时间。使用流量影响线计算流量时不需要流域面积,可以减少外业工作量。无论是已经建立单位线的地区还是没有建立单位线的地区,都可以利用流量影响线法预报山洪对中小桥的影响。流量影响线法可以为抗洪提供科学依据,为行车安全与抢险赢得宝贵的准备时间。

Flow Influence Line and Its Application in Bridge Flood Forecast

On the basis of the unit hydrograph method,the flow influence line method is put forward.The mathematical model of the flow influence line has the same form with the stress influence line of the simply supported beam.So the computation process of peak flood flow is transformed into critical loading on the influence line in structural mechanics.Calibration of the flow influence line can be done depending on water marks on piers left by flood in history and the corresponding rainfall series;new rainfall series are applied on the calibrated flow influence line as mobile loading,and the runoff process curve can be got;finally,the peak flood flow and the time it gets to the bridge site,namely the peak time,are fixed according to the runoff process curve.Computing flow through the flow influence line does not need drainage area,so field work can be largely cut down.Damages to middle and small bridges caused by mountain floods may be predicted with the flow influence line method,no matter the bridges are located in regions with or without the unit hydrograph.The flow influence line method can provide scientific criterion and gain precious preparation time for guarantee of traffic safety and flood fighting.