How to Make Steel Bridges More Durable

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Abstract: Steel bridges have been used in US for over one hundred years. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. In some cases, the plate girders may be formed in a Z-shape rather than I-shape. The first tubular wrought iron plate girder bridge was built in 1846-47 by James Millholland for the Baltimore and Ohio Railroad. As of today, The I-64 Kanawha River Bridge sets the record as the longest-span steel plate girder bridge in the United States, with its 562-foot main span. This paper presents the methods to make steel bridges more durable. The weathering steel, galvanized steel, and metalizing steel will be reviewed. The jointless bridges are presented as well.

Keywords: steel plate girder, durable, durability, weathering steel, galvanized steel, metalizing steel, bridges, US.

Introduction

Steel bridges have the following advantages:

1. Longer spans,

2. Much easier to meet minimum clearance requirements

Steel bridges have the following disadvantages:

1. Need to paint the steel bridge about every 25 to 30 years, which will increase maintenance cost. One way to reduce the maintenance cost is to use galvanized steel or metalized steel or weathering steel.

2. End of girders are very easy to get corroded under expansion joint in cold regions where salt or deicing materials are used in the winter time.

Concrete bridges have the following advantages:

1. Less maintenance cost than steel bridges

2. Speed up construction, or ABC (Accelerated Bridge Construction)

3. In most cases, concrete bridges are cheaper than steel bridges.

Concrete bridges have the following disadvantages:

1. Difficult to repair the damage by collision

2. Difficult to repair the cracks and spalls

Steel bridges have been used in US for over one hundred years. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. In some cases, the plate girders may be formed in a Z-shape rather than I-shape. The first tubular wrought iron plate girder bridge was built in 1846-47 by James Millholland for the Baltimore and Ohio Railroad. As of today, The I-64 Kanawha River Bridge sets the record as the longest-span steel plate girder bridge in the United States, with its 562-foot main span. This paper presents the methods to make steel bridges more durable. The weathering steel, galvanized steel, and metalizing steel will be reviewed. The jointless bridges are presented as well.

The best way to prevent deterioration on steel bridges is to eliminate deck joints! In fact, for many short span steel bridges, deck joints are not needed at all. If steel girders are discontinuous, consider using link slabs to eliminate deck joints.

Painting on Steel (Google 2 (2024))

Painting on steel is most commonly used method in US to project.

What is painted steel? As the name suggests, painted steel is exactly that: a layer of paint is applied to steel, creating a protective layer from the elements. The process of applying paint to steel involves: Cleaning the steel using a technique called sandblasting.

After painting, different color can be applied to painted steel depending on the DOT’s requirement on color.

Sun, heat, wind and weathering are constants that result in paint typically requiring touch-up and replacement in 12-15 years, costing far more than galvanizing over the intended life of the project.

Some of the cons of choosing painted steel are:
Cost of the paint and its application. With an epoxy paint, paint can fade unevenly depending on where the parts of a structure may face – i.e., one section of a structure may be exposed to more sun than another section, causing an uneven fade over time.

Epoxy Steel Painting: Epoxy Paintings are one of the most widely used steel coatings in industrial and marine markets. Polyurethane Steel Painting: Polyurethane paintings are often used as topcoats over epoxy primers on structural steel.

How do you permanently paint steel?

Apply primer in a well-ventilated area as directed by the manufacturer and allow it to dry. Use a clean brush to apply an even coat of paint to the prepared stainless steel surface. Allow the first coat to dry for the amount of time directed by the manufacturer. Apply the second coat.

Is it better to paint steel or galvanized steel?

Galvanized metal is more durable, but the upfront cost is more expensive than a painted coating. Galvanizing can cost about twice as much per pound as it would to paint the metal, depending on the paint specifications. However, repainting can get expensive if it needs to be done every 10 years, or sooner in some cases.

What is the most durable paint for steel?

-IT® protective paint for STEEL-IT® protective paint for metal is exceptionally durable. Lasting admirably for 10+ years in most environments, it withstands scratching, denting, abrasion, corrosion, high water or air pressure, turbulent and harsh climates, rough factory conditions, and UV radiation.

Weathering Steel (Google 3 (2024))

Weathering steel definition: steels that are chemically formulated to develop a protective patina layer – rust-like in appearance – that eliminates the need for paint. The dense oxide patina layer of weathered steel seals it off from the atmosphere. If a weathered steel panel is scratched, its patina will self-heal.

How long does weathering steel last?

If the planter does not offer adequate drainage, the steel may not dry out, and rather than forming a patina, it may begin to rust through at a quicker rate. Under ideal circumstances, weathering steel can last for decades.

One of cons for using weathering steel is it is not convenient to perform bridge inspection.

The following is the limitations to use weathering steel per FHWA guideline. Under the following conditions, weathering steel should be avoided.

1. Environmental/Climatic factors effecting the selection of

type of steel for new structures.

(a) Marine Coastal Areas

(b) Areas of Frequent High Rainfall, High Humidity or Persistent Fog

2. Geometric and location features considered for new

structures.

(a) Grade Separations - the so-called "tunnel effect" is

produced by the combination of narrow depressed roadway

sections between vertical retaining walls, narrow shoulders,

bridges with minimum vertical clearances and deep abutments

adjacent to the shoulders as are found at many urban/suburban

grade separations. These roadway/bridge geometrics combine

to prevent roadway spray from being dissipated by air currents

and can result in excessive salt in the spray being deposited on

the bridge steel. The illustration below is representative of

situations where use of uncoated weathering steel should be

avoided where winter deicing salt use is significant.

Depressed Roadway: Tunnel-like Condition

(b) Low Level Water Crossings - sufficient clearance over

bodies of water must be maintained so that spray or

condensation of water vapor does not result in prolonged

periods of wetness of the steel. Clearance to bottom flange of

at least 10 feet over sheltered, stagnant water and at least 8

feet over running water is recommended.

1. Design details for new structures.

(1) Controlling Roadway Drainage - This is the first line of defense

against localized corrosion -eliminating the exposure of the steel to

contact with drainage from the roadway above, especially in areas

where roadway salts are used.

(a)Joints:

(b)Scuppers:

(2) Other Features:

(a) Water Traps

(b) Box Sections

(d) Overlapping surfaces

4. Maintenance actions to maximize the service life of existing

structures.

Maintenance Actions - effective inspection and maintenance programs are

essential to ensure that all bridges reach their intended service life. This is

especially true in the case of uncoated weathering steel bridges. The

following maintenance actions should be routine:

(1) Inspection

(2) Controlling Roadway Drainage

order to divert deck drainage away from the superstructure

steel and substructure units.

(d) Periodically clean and repaint all steel within a minimum

distance of 1 1/2 times depth of the girder from bridge joints.

(3) Other Maintenance

(a) Remove dirt, debris and other deposits that hold moisture

and maintain a wet surface condition on the steel. In some

situations, hosing down a bridge to remove debris

andcontaminants may be practical and effective. Some

agencies have a regularly scheduled program to hose down

their bridges.

(b) Maintain screens over access holes in box sections to

prevent entrance by animals and birds.

natural drying of surfaces wet by rain, spray or other sources of

moisture.

Galvanized Steel (Google 4 (2024))

Does galvanized steel rust?

Galvanized steel takes a long time to rust, but it will eventually rust. This type is carbon steel that has been galvanized or coated with a thin layer of zinc. The zinc acts as a barrier preventing oxygen and water from reaching the steel, providing advanced corrosion protection.

It can play an important role for buildings, bridges, facades, signal gantries, gates, balconies and even sculptures. Wherever there is a risk for corrosion of steel, galvanizing should be used.

In a recent IL DOT (department of transportation) project “Circle Interchange Project”, all the straight steel girders are galvanized to reduce future maintenance cost.

Metalizing Steel (Google 5 (2024))

Metallizing is the general name for the technique of coating metal on the surface of objects. Metallic coatings may be decorative, protective or functional.

Techniques for metallization started as early as mirror making. In 1835, Justus von Liebig discovered the process of coating a glass surface with metallic silver, making the glass mirror one of the earliest items being metallized. Plating other non-metallic objects grew rapidly with introduction of ABS plastic. Because a non-metallic object tends to be a poor electrical conductor, the object's surface must be made conductive before plating can be performed. The plastic part is first etched chemically by a suitable process, such as dipping in a hot chromic acid-sulfuric acid mixture. The etched surface is sensitised and activated by first dipping in tin(II) chloride solution, then palladium chloride solution. The processed surface is then coated with electroless copper or nickel before further plating. This process gives useful (about 1 to 6 kgf/cm or 10 to 60 N/cm or 5 to 35 lbf/in) adhesion force, but is much weaker than actual metal-to-metal adhesion strength.

Vacuum metallizing involves heating the coating metal to its boiling point in a vacuum chamber, then letting condensation deposit the metal on the substrate's surface. Resistance heating, electron beam, or plasma heating is used to vaporize the coating metal. Vacuum metallizing was used to deposit aluminum on the large glass mirrors of reflecting telescopes, such as with the Hale telescope.

Thermal spray processes are often referred to as metallizing. Metals applied in such a manner provide corrosion protection to steel for decades longer than paint alone. Zinc and aluminum are the most commonly used materials for metallizing steel structures.^[1]

Cold sprayable metal technology is a metallizing process that seamlessly applies cold sprayable or putty able metal to almost any surface. The composite metal consists of two (water-based binder) or three different ingredients: metal powder, binder and hardener.

The mixture of the ingredients is cast or sprayed on the substrate at room temperature. The desired effect and the necessary final treatment define the thickness of the layer, which normally varies between 80 and 150 µm.

In a recent IL DOT (department of transportation) project “Circle Interchange Project”, all the curved steel girders are metalized to reduce future maintenance cost since galvanizing tub is not wide enough to galvanize curved girders. The SW flyover girders are metalized.

Jointless Bridges/Integral Abutments/Semi-Integral Abutments

Google 6 (2024), Google 7 (2024)

Integral abutments or semi-integral abutments are used to eliminated joints at abutments.

In the United States of America (USA), there are more than 9,000 Fully Integral Abutment Bridges and 4,000 Semi-Integral Abutment Bridges. Integral Abutment Bridges have proven themselves to be less expensive to construct, easier to maintain, and more economical to own over their life span

An integral bridge contains no expansion joints to accommodate enlargement due to increased temperature. Horizontal (axial) movements due to thermal expansion and braking loads are instead transferred to the fill adjacent to the abutment. The omission of the expansion joint removes a pathway for the penetration of chloride-bearing road salts to the bridge's sub-structure. In the United Kingdom there is a presumption that most new short to medium length bridges will be of the integral type.

An early example of an integral bridge is masonry arch bridge. Some of the earliest examples of integral bridges in reinforced concrete were constructed as part of the United Kingdom's M1 motorway in 1959.

Conclusions

Steel bridges have been used in US for over one hundred years. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. In some cases, the plate girders may be formed in a Z-shape rather than I-shape. The first tubular wrought iron plate girder bridge was built in 1846-47 by James Millholland for the Baltimore and Ohio Railroad. As of today, The I-64 Kanawha River Bridge sets the record as the longest-span steel plate girder bridge in the United States, with its 562-foot main span. This paper presents the methods to make steel bridges more durable. The weathering steel, galvanized steel, and metalizing steel are reviewed. The jointless bridges are presented as well.