Scour around bridge piers

Scour around Bridge Piers.
Mohammad saeed khawam 201401379
Walid Omairi 201401485
Ayman Mansour 201400917

Basic Components of a Bridge
The two basic parts are:
• Substructure - includes the piers, the abutments and the foundations.
• Superstructure - consists of the deck structure itself, which support the direct
loads due to traffic and all the other permanent and variable leads to which the
structure is subjected.
• The connection between the substructure and the superstructure is usually made
through bearings. However, rigid connections between the piers (and sometimes
the abutments) may be adopted, particularly in frame bridges with tall (flexible)
piers.

Substructure : Piers
Piers are of two basic types:
• Column piers - Concrete column piers may have a solid cross-section, or a box
section may be the shape chosen for the cross-section for structural and aesthetic
reasons.
• Wall piers - generally less economical and less pleasing from an aesthetic point of
view. They are very often adopted in cases where particular conditions exist, e.g.
piers in rivers with significant hydrodynamic actions or in bridges with tall piers
where box sections are adopted.

Bridge scour
Bridge scour is the removal of sediment such as sand and rocks from
around bridge abutments or piers. Scour, caused by swiftly moving
water, can scoop out scour holes, compromising the integrity of a
structure.
In the United States, bridge scour is one of the three main causes of
bridge failure
where 46 of 86 major bridge failures resulted
from scour near piers from 1961 to 1976.

Some photos of bridges failed due to the scour of foundation material.
Effects of Scour Lowering the river bed level around Pier
Destabilize the Foundation(Pier)

Piles exposed to river due to large scour

Mechanism of Scour
Development scour hole:
Vortex system formed in front of the
obstruction, and has the form of horseshoe
River flow and boundary condition give rise
to the energy of the vortex Increased shear
stress commence local
sediment transport

Local Scour at Piers
• Occurs due to the acceleration of flow around the pier and the
formation of flow vortices.

A bridge in the dry season in Sudan

Shearing Stress Calculation
scourscour
scour

Protection :
Gravel bags : put around pies used for
filter function to reduce flow but
disadvantages handling cost and potential
damage to bags during installation and
after a time loose rock due to flow

Rock Channel Protection at Bridges

Thank you
Mohammad saeed khawam ---Walid Omairi --- Ayman Mansour

Scour around bridge piers

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