Orthotropic deck
Encyclopedia
Structural steel
Structural steel is steel construction material, a profile, formed with a specific shape or cross section and certain standards of chemical composition and mechanical properties...
deck plate stiffened either longitudinally or transversely, or in both directions. This allows the deck both to directly bear vehicular loads and to contribute to the bridge
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
structure's overall load-bearing behaviour. The orthotropic deck may be integral with or supported on a grid of deck framing members such as floor beams
Beam (structure)
A beam is a horizontal structural element that is capable of withstanding load primarily by resisting bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment.- Overview...
and girder
Girder
A girder is a support beam used in construction. Girders often have an I-beam cross section for strength, but may also have a box shape, Z shape or other forms. Girder is the term used to denote the main horizontal support of a structure which supports smaller beams...
s.
The same is also true of the concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
slab in a composite girder bridge, but the steel orthotropic deck is considerably lighter, and therefore allows longer span bridges to be more efficiently designed.
The stiffening elements can serve several functions simultaneously. They enhance the bending
Bending
In engineering mechanics, bending characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element. The structural element is assumed to be such that at least one of its dimensions is a small fraction, typically...
resistance of the plate to allow it to carry local wheel loads
Structural load
Structural loads or actions are forces, deformations or accelerations applied to a structure or its components.Loads cause stresses, deformations and displacements in structures. Assessment of their effects is carried out by the methods of structural analysis...
and distribute those loads to main girders. They also increase the total cross-sectional area of steel in the plate, which can increase its contribution to the overall bending capacity of the deck (i.e. the deck plate acts as a top flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
in a box
Box girder
A box or tubular girder is a girder that forms an enclosed tube with multiple walls, rather than an or H-beam. Originally constructed of riveted wrought iron, they are now found in rolled or welded steel, aluminium extrusions or pre-stressed concrete....
or I beam girder). Finally, the stiffeners increase the resistance of the plate to buckling
Buckling
In science, buckling is a mathematical instability, leading to a failure mode.Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium...
.
A German Engineer Dr. Cornelis of MAN Corporation was issued German patent No. 847014 in 1948. MAN's design manual was published in 1957 in German. In 1963 AISC published their manual based on North American design practices today called AASHTO.
Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck....
s and suspension bridge
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...
s) would not be feasible without steel orthotropic decks. The longest or record span box girder
Box girder
A box or tubular girder is a girder that forms an enclosed tube with multiple walls, rather than an or H-beam. Originally constructed of riveted wrought iron, they are now found in rolled or welded steel, aluminium extrusions or pre-stressed concrete....
, slant-leg bridges; arch bridge
Arch bridge
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...
s; movable bridges and two Norwegian Floating Bridges. (The steel deck-plate-and-ribs system may be idealized for analytical purposes as an orthogonal
Orthogonality
Orthogonality occurs when two things can vary independently, they are uncorrelated, or they are perpendicular.-Mathematics:In mathematics, two vectors are orthogonal if they are perpendicular, i.e., they form a right angle...
-anisotropic
Anisotropy
Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties An example of anisotropy is the light...
plate, hence the abbreviated designation “orthotropic.”) Thousands of orthotropic deck bridges are in existence throughout the world. Despite the savings and advantages (up to 25% of total bridge mass can be saved by reducing deck weight, as the weight reductions extend to cables, towers, piers, anchorages, and so forth), the US has only about 60 such bridge decks in use as of late 2005. About 25% of USA Orthotropic Steel Deck Bridges are in California, including the San Mateo-Hayward Bridge box girder
Box girder
A box or tubular girder is a girder that forms an enclosed tube with multiple walls, rather than an or H-beam. Originally constructed of riveted wrought iron, they are now found in rolled or welded steel, aluminium extrusions or pre-stressed concrete....
(1967) one of the first major bridges in the US to be built using an orthotropic deck.
Three "basic types"; movable bridges, are the swing bridge
Swing bridge
A swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its centre of gravity, about which the turning span can then pivot horizontally as shown in the animated illustration to the right...
, vertical lift bridge and bascule bridge
Bascule bridge
A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....
. The El Ferdan Bridge across the Suez Canal
Suez Canal
The Suez Canal , also known by the nickname "The Highway to India", is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea. Opened in November 1869 after 10 years of construction work, it allows water transportation between Europe and Asia without navigation...
of Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
is the record span bridge. The Erasmus Bridge has an orthotropic deck for both its cable-stayed bridge
Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck....
and bascule
Bascule
Bascule may refer to:* A Bascule bridge, a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic...
span. The Danziger Bridge
Danziger Bridge
The Danziger Bridge is a vertical lift bridge which carries seven vehicular lanes of U.S. Route 90 across the Industrial Canal in New Orleans, Louisiana. It was built to replace the old Danziger Bridge, a draw bridge constructed in 1931–1932...
of New Orleans is a very large vertical lift bridge.
The Millau Viaduct
Millau Viaduct
The Millau Viaduct is a cable-stayed road-bridge that spans the valley of the river Tarn near Millau in southern France. Designed by the British architect Norman Foster and French structural engineer Michel Virlogeux, it is the tallest bridge in the world, with one mast's summit at . It is the...
a Cable-Stayed Bridge
Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck....
of Millau, France has the largest orthotropic steel deck area of any single bridge. The lower total gross weight of the superstructure allowed bridge launching from both ends of the Millau Viaduct
Millau Viaduct
The Millau Viaduct is a cable-stayed road-bridge that spans the valley of the river Tarn near Millau in southern France. Designed by the British architect Norman Foster and French structural engineer Michel Virlogeux, it is the tallest bridge in the world, with one mast's summit at . It is the...
.
The Akashi-Kaikyō Bridge's orthotropic deck allowed the Japanese to build the longest span at about 6000 ft or 50% longer than the Golden Gate Bridge
Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...
. The Italian Government is proposing to build a Messina Suspension Bridge 10,000 ft at the Strait of Messina between the Island of Sicily and Italy
Orthotropic decks permit a very shallow deck depth which reduces the steepness of approach gradients and hence their costs. The form is also widely used on bascule
Bascule bridge
A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....
and other moveable bridge
Moveable bridge
A moveable bridge is a bridge that moves to allow passage for boats or barges. An advantage of making bridges movable include lower price, due to the absence of high piers and long approaches. The principal disadvantage is that the traffic on the bridge must be halted when it is opened for passages...
s where significant savings in the cost of the mechanical elements can be made where a lighter deck is used.
The unpopularity of the orthotropic deck relates mainly to its cost of fabrication, due to the amount of welding involved. In addition, it must be prefabricated rather than assembled on site, which offers less flexibility than in-situ concrete decks. Orthotropic decks have been prone to fatigue
Fatigue (material)
'In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.Fatigue occurs...
problems and to delamination of the wearing surface, which, like the deck, is also often of a very thin material to reduce weight.
It is possible to refit a bridge originally designed with a concrete or non-structural deck to use an orthotropic deck, which was first utilized in Vancouver Canada's Lions Gate Bridge. For example, San Francisco’s Golden Gate Bridge
Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...
, completed in 1937, originally used a concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
deck
Deck (building)
In architecture, a deck is a flat surface capable of supporting weight, similar to a floor, but typically constructed outdoors, often elevated from the ground, and usually connected to a building...
. Salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
carried by fog or mist reached the rebar
Rebar
A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...
, causing corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
and concrete spall
Spall
Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...
ing. In 1985, the bridge was restored using steel deck panels. The project not only restored the bridge to prime condition but also used fewer materials and reduced the deck weight by 12,300 ton
Ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...
s (11,160 metric tons
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
).
External links
- Orthotropic bridge conference held in Sacramento, California in August 2004 & 2008.
- Turner-Fairbark Highway research center Orthotropic deck article from United States Department of TransportationUnited States Department of TransportationThe United States Department of Transportation is a federal Cabinet department of the United States government concerned with transportation. It was established by an act of Congress on October 15, 1966, and began operation on April 1, 1967...
website - Orthotropic Bridge organisation list of bridges in the US that use Orthotropic decks.
- Course outline for a design of orthotropic bridges class.
- Federal Highway Administration (US Department of Transportation) report on automation of bridge deck section fabrication.
- Chemco systems commercial site describing Epoxy Asphalt Polymer Concrete, a wear surface material that addresses the delamination problem
- Severn Crossing deck details Illustrations include deck underside and weldpoint diagrams
- Western Bridge Engineers Seminar* =orthotropic bridges of California
- [ftp://ftp.wsdot.wa.gov/public/Bridge/WBES2009/D/3D2/3D2.pdf orthotropic bridges of California]* Powerpoint
Foreign language search terms – examples of famous bridges with orthotropic steel decks
Dutch: Erasmus Orthotropic Bridge = ErasmusbrugErasmusbrug
The Erasmusbrug is a cable stayed bridge across the Nieuwe Maas river, linking the northern and southern halves of the city of Rotterdam, The Netherlands....
(Brug = bridge in Dutch)
French: Pont Gustave-Flaubert
Pont Gustave-Flaubert
The Pont Gustave-Flaubert is a vertical lift bridge over the River Seine at Rouen, Seine-Maritime, Haute-Normandie, France...
(Pont = bridge and orthotrope = orthotropic in French)
German: Erasmus-Brücke (Brücke = bridge and orthotrop = orthotropic in German)
Brazilian Portuguese: The Juscelino Kubitschek Bridge
Juscelino Kubitschek bridge
The Juscelino Kubitschek Bridge , also known as the President JK Bridge or just the JK Bridge, is a steel and concrete bridge that crosses Lake Paranoá in Brasília. It links the southern part of the lake, and St. Sebastian Paranoá the Pilot Plan , through the Monumental Axis...
(Portuguese: Ponte Juscelino Kubitschek) (Ponte = bridge in Portuguese)
Italian Ponte sullo Stretto di Messina (Ponte = Bridge in Italian)
Norwegian: Nordhordland Bridge
Nordhordland Bridge
The Nordhordland Bridge is a combined cable-stayed and pontoon bridge which crosses Salhusfjorden between Klauvaneset and Flatøy in Hordaland, Norway. It is long, of which the pontoon section is long. The cable-stayed section consists of a single tall H-pylon which has a length of and a main...
= Nordhordlandsbrua (Brua = bridge in Norwegian)