Bridge Hydraulics

Bridge Hydraulics

Many people, indeed many engineers, who are not familiar with the subject imagine that
constructing a bridge across a river is entirely a problem in structural engineering. They
assume that the bridge opening can be made so large that it will completely span the river at
such a height that floodwater will never rise anywhere near the deck. If this was always true
there would be little need to study bridge hydraulics, but in reality things are rarely this simple.
Economics often dictate the length of span and therefore how many piers have to be located in
the river. Similarly economics, the geography of the site or the nature of the crossing (such as
a railway line with a fixed vertical profile may impose some restriction on the
maximum permissible elevation of the deck. Consequently flood levels may rise to deck
height or above. What initially appeared to be an elementary problem turns out to be quite

This book is concerned with the hydraulic analysis and design of bridge waterway openings.
It covers both single and multispan bridges with either rectangular or arched waterways. It is
based on a century or more of study and research by investigators all over the world, most
notably in North America. It can be used to estimate how a bridge, existing or proposed, will
alter water levels at a site at any particular discharge. Conversely, it can be used to calculate
the discharge from the observed water levels. It can be employed to analyse and design
modern bridges with relatively long rectangular spans, or to investigate the hydraulic
performance of the old masonry arch structures that are still numerous in many parts of the
world. Other topics covered include how to improve the flow through a bridge, and how to
evaluate and alleviate the problem of scouring of the foundations.


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