New footbridge in Seatown, Cullen requires protective system for harsh environments due to North Sea location

CTS Bridges supply their footbridges with a variety of high quality protective finishes depending on the bridge location. But for a recent bridge installation in Cullen, Morayshire the requirement was for a paint system to suit a harsh environment due to its exposure to the North Sea.

Vierendeel Truss cycleway bridge at Cullen, Morayshirectsbridges1216a
Original concrete bridge – Built in 1930’s

Original concrete bridge – Built in 1930’s

A new cycle/footbridge was recently installed by CTS Bridges in the town of Cullen, Morayshire. The new bridge replaces an old concrete structure built in the 1930’s which was in very poor condition.

New Footbridge awaiting top coat

New Footbridge awaiting top coat

The new bridge forms part of the Moray Coast Trail and is 3m wide to accommodate both cyclists and pedestrians on what is one of the busiest footbridges in the area due to its proximity to the beach car park and golf club.

Due to its location next to the North Sea a Series 1900 paint specification for difficult access was used which will give the bridge a life to first major maintenance of 20 years.

The paint system comprises of:

– Blast clean to SA3 Standard
– 1 coat HB Epoxy Zinc Rich Primer Dpt Item 109 –- MDft 50 microns
– 2 coats HB Epoxy MIO Dpt Item 112 – MDFT 125 microns/coat
– 1 coat Polyurethane Finish Dpt Item 169 – 870 – MDFT 50 microns
– Top coat colour – Power Blue BS4800 20C33.

Aerial view of bridge showing its proximity to the North Sea

Aerial view of bridge showing its proximity to the North Sea

Mr David Walker, a local resident, kindly sent us these photographs and commented “The bridge has been very well received and is something of a talking point among those who use it and who like to visit Cullen.”

Footbridge Protective Systems: 

There are differing types of protective systems available for bridges. These can be either painted, galvanised (or a combination of Galvanised and painted) or weathering (Corten) steel.

The type of protective finish affects both the performance and budget. However the choice of protective system depends also on the Environment (either inland or marine) and accessibility (ready or difficult access). Difficult access applied where future maintenance painting activities including inspections and trails would require some form of traffic management and/or temporary access works.

Painted finish:

Our Steel truss or beam bridges have two main paint systems – namely:

Type 1 for Ready Access Type 2 for Difficult Access
Shot blast to SA 2.5 Min DFTh or Shot blast to SA 3 Min DFTh
1 coat 2 pack epoxy zinc phosphate primer 125 microns or 1 coat of HB Epoxy Zinc Rich Primer (Dtp Item 109) 50 microns
1 coat 2 pack epoxy MIO undercoat 125 microns or 1 coat of HB Epoxy MIO (Dtp Item 112) 125 microns
1 coat 2 pack polyurethane finish (to single colour of choice) 50 microns or 1 coat of HB Epoxy MIO (Dtp Item 112) 125 microns
1 coat of Polyurethane Finish (Dtp Item 169) 50 microns
This system will give a life to major maintenance of 15 – 20 years. This system complies with SHW Series 1900 and will give a life to major maintenance of 20 – 25 years in an environment defined as exterior exposed inland with difficult access.

The service life quoted above is subject to the environment the bridge is placed in.

Or we can provide Type 5 for Ready or Difficult Access that provides an Aluminium metal spray, plus sealer, Plus quick drying epoxy (two pack) system with an epoxy acrylic, polyurethane or polysiloxane finish.  This finish provided no maintenance up to 12 years, minor maintenance from 12 years and major maintenance after 20 years.

For Highways bridges or bridges on other trunk roads we supply a completed Appendix 19/1 Form HA/P1 paint system sheet.

Galvanised finish:

On steel beam bridges you can have a galvanised finish. A galvanised finish will give an average life of 20 years without maintenance but can be up to 40 years depending on the environment. The Engineers and Architects Guide to Hot Dip Galvanising states a life of 34 to 70 years depending on area. Our bridges are galvanised in accordance with BS 1461. This finish provides an economical option with minimal maintenance.

Galvanised and painted:

It is quite common to have both Galvanised and painted finishes on a bridge in accordance with series 1900. Many customers request galvanised main beams and a painted system for the parapets to a colour of their choice. The top coat colour is identified by means of a colour description and a BS or RAL number i.e. Dark Grey – BS18B25.

Corten / Weathering Steel

Weathering steel is a high strength low allow steel originally developed in the USA to resist corrosion and was given the trade name Cor-ten. In suitable environments the steel forms an adherent protective rust patina that inhibits further corrosion. This type of finish is not suitable for bridges in coastal environments. It has very low maintenance requirements and is ideal where access for future maintenance is difficult or dangerous. However it is a more expensive option. For more information on Weathering steel see http://www.steelconstruction.info/Weathering_steel.

CTS Bridges employ both skilled joiners and fabricators and can therefore provide an extensive range of bridges in a variety of materials including steel and FRP or using a combination of steel, timber or FRP materials.

ctsbridges1216logoPlease contact us for more details on our design, build and installation service for bridges and structures on 01484 606416 or visit our website at www.ctsbridges.co.uk or by email enquiries@ctsbridges.co.uk