Physical failure will not normally occur from wave or current forces if 

 steel structures are properly designed. Primary cause of failure will be 

 severe damage by ships, barges or debris, or in the case of a dock, through 

 overloading. Prompt replacement of buckled members is mandatory to prevent 

 further damage to adjacent members. 



e. Wood . The greatest cause of deterioration of wooden structures is 

 biological attack. This may be by plant or animal life and may occur 

 completely above or below the waterline but is most likely to occur in the 

 wet dry tidal area. Most of these species require some sunlight but there 

 are some that are active in total darkness. Only below the mud line are 

 wood members safe from such attack. Two methods of preventive maintenance 

 are available—complete impregnation of the cells of the wood by 

 chemicals, or the application of a surface coating that prevents entry of 

 borers into the timber. Surface coatings may be coatings such as antifouling 

 paint or a coating material resistant to borer penetration, such as a 

 thick, 0.5-millimeter (0.020 inch), epoxy coating, a synthetic film wrapped 

 around the wood members or a membrane of concrete (usually about 50 milli- 

 meters thick) completely surrounding the wood members. Without such protec- 

 tion, a wood structure will deteriorate rapidly making a sustained mainten- 

 ance program of inspection and prompt replacement necessary to a long 

 service life of the structure. 



Physical damage generally consists of broken members due to damage by 

 ships, barges, or debris, or by the force of storm waves. Prompt replacement 

 of broken members is necessary to avoid deterioration of adjacent members. 

 Damage through chemical reaction is largely confined to unusual events in 

 industrial harbor basins. A side benefit of pollution of harbor waters 

 from industrial activity may be the almost complete absence of marine life 

 that attack wooden structures. 



f . Asphalt . This is primarily used as a surfacing material for 

 harbor roads, parking areas, and storage zones. It is subject to chemical 

 deterioration, abrasion, plastic flow under heavy loads, and vehicular 

 impact, particularly in areas subjected to high temperatures. Continuous 

 maintenance is required or damage will not only be extensive to the asphalt 

 structure, but also to vehicles and equipment using it. Where asphalt is 

 used on jetties, frequent inspection and replacement of broken or dislodged 

 asphalt is required. 



7 . Environmental Considerations . 



The physical properties and performance experience of each of the 

 coastal structural materials are discussed in detail in the following 

 sections. The environmental impacts considered on each of the materials 

 are: corrosive and pollutant attacks on exposed surfaces, the effects of 

 sunlight, water penetration, waves and currents, severe temperature, ice, 

 marine organisms, periodic wetting and drying, wind erosion, burrowing 

 animals, flora, fire, abrasion, seismic effects and human activity. While 

 all of the above impacts do not effect all structural materials (for example, 

 fire does not change the physical properties of earth), those environmental 

 impacts that may effect a specific structural material to be considered for 

 use in coastal construction are discussed in the appropriate material 

 section. 



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