Bridge deck drainage

Last updated on Wed, 05/11/2016 - 11:27

Well designed bridge deck drainage is an essential aspect of road safety.
Bridge deck drainage is made with collectors either installed within the archstones or underdeck exposed, and then through vertical stacks.

Basing on precise project criteria – run-off type, rainfall intensity, slope and surface of the catchment area etc...- the designer will size up the drainage project and select the outlet types.

SAINT-GOBAIN PAM, municipal castings number one in Europe, has developed an expert software to guide the designer in selecting the inlets and sizing up the drainage project.

Life expectancy of bridges and civil works

Their life expectancy is generally set around 50 years, but the longer the better.
Engineering structures can be exposed to extremely adverse climatic conditions: exposure to ultra-violets, gusts of wind, weather stresses...

Bridge decks can also expand in two axis.

It is of utmost importance to select a pipe system able to withstand to one constraint and the other because a good drainage protects the bridge lifespan.

Cast iron resistance to climatic stresses and its low thermal expansion coefficient, very close to steel or concrete, make it the ideal material for this application. The jointing of the cast iron systems is made with couplings equipped with elastomer gaskets able to absorb potential small range movements.

All these characteristics build reliable and long lasting drainage systems, able to withstand operation constraints.

The expansion values are determined by the civil work designer. Where these values are very high, specific devices must be considered during the drainage system installation, to accommodate movements in the structure.

Protection and safety against fire hazards

On the roads, accidents may occur involving cars or trucks and their loads. The risks of fire are very high and the site conditions make the rescue very difficult. Drainage systems must not feed the fire nor worsen the risks.

According to the Euroclass classification, the ITINERO range fire ranking is A2, s1-d0.

Non-flammable and non combustible, the pipe system will not give off toxic smokes nor burning droplets and will not feed the fire in case of accident.

Fitness for purpose and ease of installation

Bridges impose many building constraints: reduced accessibility and operability, quick installation required etc…
Bridge deck drainage systems have to be solid, easy to install and to maintain.

SAINT-GOBAIN PAM cast iron pipe systems are available in a range of diameters from 50 up to 600, to suit all sites configurations and build consistent pipeworks.

PAM cast iron are solid and modular systems to ease handling and installation.

  • Suitably long pipes (3m)
  • Dismountable or adjustable mechanical couplings.
  • Many pieces to ease assemblies

The couplings angular deflections (3° or 1,5° according to the diameter) allow to follow large curvatures without additional fittings. The jointing is made with stainless steel couplings and allows reversible assemblies, for maintenance or part repair.

Cast iron spigot systems are easily cut to length and can be passed through manholes.

Respect for the environment

Drainage systems collect run-off waters but also drain silt, debris and contaminants (heavy metals…) from the pavement. Bridges often straddle rivers or wetlands not to be contaminated.

SAINT-GOBAIN PAM cast iron pipe systems are perfectly watertight to prevent leaks to the natural environment.

Their external coatings accept all finish paints and can be colour matched for a perfect integration into the bridge

Our recommendations

Run-off waters commonly contain waste materials, heavy metals or hydrocarbon traces. In winter, in some cold regions, they can also contain de-icing salts.

The ITINERO range we recommended for these applications have an internal lining able to resist pollutants and run-off water collection and an external coating fully adapted to resist environment and climatic stresses (see FOCUS).

However, when the pipe system is inside the bridge, or if a specific anti-corrosion coating is applied, the standard range SMU S can also fit. Please consult us.