j. Fire. Metals in the shapes and sizes used in construction will not 

 burn in a fire; however, these do have reduced strength as temperatures 

 rise. Carbon steel is affected above 340 Celsius (650 Fahrenheit). At 

 480° Celsius (900° Fahrenheit), carbon steel has only about half the strength 

 that it does at room temperature. During a fire, structures of all steel 

 construction have collapsed. Structures are protected from fire loss by the 

 installation of sprinkler systems, which spray water on the building and 

 roof supports to keep them cool and by the covering of steel beams and 

 supports with concrete to provide insulation. Metals that have experienced 

 a fire should be tested for suitability before being reused because strength 

 and toughness may be reduced. Heat treatment may be required to restore 

 properties. 



k. Human Activity. Accidents and theft are two elements of human 

 activity that the designer must consider. Piers and wharves are constructed 

 with fender systems to minimize damage from impact by ships. When accidents 

 do cause damage, metal structures may be repairable by welding. 



Legs on drilling platforms are often sheathed with copper nickel alloys 

 in the splash zone areas to minimize corrosion. Attempts to use similar 

 methods in harbors have not been completely successful because the sheathings 

 have been stolen for their metal value as scrap. 



4. Uses of Structural and Sheet Metal. 



a. General. 



(1) Steel. Various parts of coastal structures are made of steel. 

 Steel H-piles or pipe piles are used to support foundations. Steel H-piles 

 are used in preference to steel pipe piles because they are more easily 

 driven in soils containing hard strata or obstructions such as boulders. 

 Steel H-piles are easily spliced by welding, allowing driving to deep rock 

 strata if necessary. Steel H-piles are also frequently used to support 

 fender systems immediately in front of the wharves. Steel bolts are used to 

 attach rubber bumpers to the fender system that prevents damage to the 

 structure by absorbing the ship impact loads. Cast-steel bollards and 

 mooring posts are used to take up ships' lines. Steel is an ideal material 

 for breasting and mooring dolphins because steel can be easily jointed, has 

 high tensile strength, good ductility, and good toughness. Structural steel 

 shapes are used for framing of structures. Even the fences around coastal 

 installations are most often chain- link steel fences. 



Large quantities of steel are used in components that appear to be all 

 concrete. Concrete piles, beams, structure foundations, walls, roadways, 

 and pads all will contain steel reinforcing bar, wire or wire fabric. 

 Materials for concrete reinforcement are covered in Section V, Portland 

 Cement Concrete. 



(2) Aluminum . Many alloys of aluminum possess high corrosion 

 resistance to marine atmospheres as well as good strength-.to-weight ratios. 

 These properties make aluminum an economic choice for many applications in 

 coastal structures, particularly where freedom from maintenance is desired. 



225 



