Bridge protection systems
Bridge protection systems prevent ship collision damage to a bridge by either deflecting an aberrant ship from striking the piers of a bridge, or sustaining and absorbing the impact.[1]
History
Protecting bridges against
In the US, the turning point was the collapse of the Sunshine Skyway Bridge in 1980. Since then,[2]
- A "Committee on Ship/Barge Collision" appointed by the National Research Council issued a report on the history of ship collisions with bridges[3](1983);
- The Louisiana Department of Transportation and Development issued vessel collision protection criteria for the bridge piers in Louisiana (1984);
- Eleven states together with the Federal Highway Administration commissioned guidelines for the bridge protection design in the United States (1988);
- The American Association of State Highway and Transportation Officials (AASHTO) issued a Vessel Collision Design Guide Specification[4] in February, 1991, based on the previous study;
- The International Association for Bridge and Structural Engineering published its "Ship Collision with Bridges"[5] guide in 1993;
- AASHTO adopted the LRFD bridge design specifications[6]with provisions for bridge protection (1994).
Designs
There are several types of bridge protection systems used:[7]
- Fender systems attached to the pier with the goal to absorb the vessel impact. Their ability to withstand a typical ship collision is low. Fenders are built using a variety of materials:[8]
- thin-walled concrete box;
- thin-walled steel membrane steel;
- rubber.
- artificial islands built with sand and rock core that is protected by riprap. The islands are quite effective in protecting the pier by pushing the ship away, but cause environmental damage to the river bottom and, while settling, might shift the bridge piers;[8]
- piles driven into the river bottom in a group, with space in between sometimes filled with rocks and capped with concrete. The collision is absorbed via deformations of the structure;[8]
- pile-supported systems on dedicated piles that are driven into the bottom either vertically or at an angle ("batter piles"). The piles are connected together with rigid or flexible links, can be attached to the pier, and sometimes are fitted with fenders;[8]
- floating systems (cable nets and pontoons) have multiple problems from low efficiency to high construction and maintenance costs and environmental impacts, and are therefore used as a last resort, when the location of the bridge precludes the use of other designs.[8]
- Starlings are widenings of the bridge piers near their base, typically extending some distance above water level, providing some degree of reinforcement of the pier against impact.[9]
Alternatives
Physical bridge protection systems designed to prevent catastrophic collisions are expensive and represent a "significant" share of overall construction costs. Therefore, alternatives are typically considered during the design phase:[10]
- fortifying the piers and superstructure to the point where they will be able to handle the impact, either on their own, or with the help of a fender system;
- increasing the span length, so that the piers are away from the fairway and thus protected by the shallow water around them;
- improving the
Regulations
Highway designs in the US are subject to the AASHTO specifications,[4][6] but the text does not contain specific procedures and recommendations.[2] Railway bridges are build according to the "Manual for Railway Engineering"[12] published by the American Railway Engineering and Maintenance-of-Way Association (AREMA).[8]
In Australia, the subject is covered in the Australian standard AS 5100.2:2017, "Bridge design, Part 2: Design loads".
References
- ^ Knott & Prucz 2000, 60.2.5.
- ^ a b c Knott & Prucz 2000, 60.1.1.
- ^ National Research Council, Ship Collisions with Bridges — The Nature of the Accidents, Their Prevention and Mitigation, National Academy Press, Washington, D.C., 1983
- ^ a b AASHTO, Guide Specification and Commentary for Vessel Collision Design of Highway Bridges. American Association of State Highway and Transportation Officials, Washington, D.C., 1991.
- ISBN 978-3-85748-079-9. Retrieved 2024-03-30.
- ^ a b AASHTO, LRFD Bridge Design Specifications and Commentary, American Association of State Highway and Transportation Officials, Washington, D.C., 1994.
- ^ Wuttrich et al. 2001, p. 17.
- ^ a b c d e f Knott & Prucz 2000, 60.8.1.
- ^ "Parts of a bridge and gloss". scotlandsoldestbridges.co.uk. Retrieved 29 March 2024.
- ^ Knott & Prucz 2000, 60.8.
- ^ Knott & Prucz 2000, 60.8.2.
- ^ AREMA, Manual for Railway Engineering, Chapter 8, Part 23, American Railway Engineering Association, Washington, D.C., 1999.
Sources
- Knott, Michael; Prucz, Zolan (2000). "Vessel Collison Design of Bridges". Bridge Engineering Handbook (PDF). Boca Raton: CRC Press.
- Wuttrich, Rafal; Wekezer, Jerry; Yazdani, Nur; Wilson, Claudia (2001). "Performance evaluation of existing bridge fenders for ship impact". Journal of Performance of Constructed Facilities. 15 (1): 17–23. .