ABSTRACT
Usually bridge hydraulics is concerned w i t h determining either the stage-discharge relationship of a structure or the afflux, or possibly both. This chapter shows how to analyse the flow through rectangular and arched bridge waterway openings wi th either single or multispans, before and after the waterway becomes drowned. The abutments provide the primary contraction, wi th the piers being a secondary influence: often the gross area of the waterway opening ( A N 2 , which includes the area occupied by any piers) is employed initially in the calculations, and then a correction factor (/) is introduced to allow for the secondary obstruction of the piers. Typically / = A P / A N 2 where A P is the cross-sectional area of the submerged parts of the piers projected onto section 1. On the other hand, Chapter 5 considers long crossings where i t is the piers that control the flow while the effect of the abutments is negligible.
