NJDOT Builds First Orthotropic Deck in New Jersey
- Roadway improvements of two 12’ lanes, one 12’ auxillary lane, and 8-10’ shoulder all on both sides.
- Will also include an 8’ median barrier to separate opposing traffic.
- 6’ sidewalk, will accommodate pedestrian and bicycle traffic.
- Improved vertical clearance of 70’ when closed compared to originally 35’.
- 135’ vertical clearance when raised will remain.
- Reduced opening & closing by 75%.
- Will result in reduced delays and disruptions to traffic.
What is an Orthotropic Deck?
- Steel Orthotropic Deck
- Developed in Germany in the 1930’s, similar to United States (U.S) Battleship decks.
- A thin steel plate has a series of longitudinal “ribs” and floor beams, wearing surface.
- 100% steel superstructure.
- Can see same principles on everyday level with some types of cardboard.
Why is it being used?
- Prefabricated in a shop, which results in faster construction and higher quality control.
- Lightweight, which is a critical characteristic for movable bridges.
- A lighter weight allows the bridge to be more efficient, and also allows for faster operation.
- Since the bridge is more efficient, it will require less maintenance, which will reduce lifecycle costs.
- Highly redundant system; minor cracking is often just a nuisance rather than a serious structural threat.
- Allows for longer span lengths, which provides a better riding surface than others since it contains less connections.
- Good cold weather constructability, since there is not a temperature requirement for concrete to cure.
- Corrosion resistance has historically been very good, partially from wearing surface and closed ribs.
- Unique challenges in terms of design and fabrication because of very complex welds.
- Up to this point, not very standard or common in the United States.
- Higher initial fabrication cost, but offset in the long run since less maintenance costs.
Research with Lehigh University
- Examined Prototypes of Verrazano-Narrows, Williamsburg, Bronx-Whitestone bridges (All in New York).
- Done to understand and analyze how they perform.
- Orthotropic decks are the only deck that can achieve a 100 Year Design Life, according to Dr. John Fisher.
- NJDOT looked at prototype for this deck with Dr. Sougata Roy.
- Examined 3 different connection options.
- Overall successful performance.
- Also determined critical stresses and load distribution.
- Oregon Iron Works-Vigor is manufacturing the deck.
- Expected to be completed in 2017.
- Transferred in 5 pieces for 1 month by ship.
- Shipped in 5 pieces to avoid extend closures, as less risk of delays since less field work required
- Coast Guard says channel (Hackensack River) can be closed for a max of 21 straight days.
- Erection process expected to last 14 days.
Where else are they?
- Utilized successfully for thousands of bridges worldwide (Mainly in Europe, Asia, and South America)
- “Up and Coming” type of bridge deck in the U.S. today; approximately 100 in the U.S.
- Golden Gate Bridge (California, Replacement of concrete deck in 1985 with an orthotropic deck)
- Bronx-Whitestone Bridge (NY) , Verrazano-Narrows Upper Deck (NY) (Orthotropic used as replacements)
- New decks on Tacoma Narrows Bridge (Washington), Alfred Zampa Memorial Bridge (California)
- Many movable bridges in Alaska as well constructed with orthotropic decks