Although the surface chars, the undamaged wood below the char retains its 

 strength. Heavy timber members will retain their structural integrity 

 throughout long periods of fire exposure because of their size and the slow 

 rate at which charing penetrates inward from the wood surface. 



1. Abrasion . In the coastal environment, abrasion of wood occurs from 

 sources such as scour by wind- and water-driven sand as well as the working 

 or rubbing at joints in the wood structure. Abrasion can be from beneficial 

 use as from vehicle traffic on a pier or from rubbing of floats on anchor 

 piles. The wearing away of a wood structure in this manner will eventually 

 reduce the structural integrity of the structure. 



m. Seismic Effects . Seismic activity can have a significant effect and 

 in some locations a devastating effect. Ground shaking can stress structures 

 to overload and cause destruction. Natural alluvial terraces or manmade 

 landfills in the coastal zone are subject to liquefaction during severe 

 earthquakes which cause the ground to slump and flow horizontally. Structures 

 founded on such terraces in a severe seismic area are subject to destruction 

 if liquefaction occurs. However, under less severe conditions, wood performs 

 very well in seismic events because of its resiliency. This characteristic 

 of wood allows it to flex during ground shaking and reduce the stresses that 

 might destroy structures of more rigid materials. 



n. Human Activity . Human use of wood structures can eventually cause 

 the wood to wear out; the worn wood parts could be replaced or the whole 

 structure could be abandoned. On wharves and piers ship moorings wear or 

 break fender piles and vehicular traffic on the deck wears out the surface 

 timbers. Human use engenders risks in the form of explosions, fires, and 

 accidental impact loads, all of which can destroy wood members of coastal 

 structures. Vandalism can cause serious damage to wood: some wood may be 

 sacrificed for firewood; wood may be destroyed by the target practice of 

 shooters; and amateur wood carvers may cause deterioration. 



12. Uses of Wood In Coastal Construction . 



a. General. 



(1) Dimension Lumber . Untreated dimension lumber can be used in 

 temporary situations during the construction phase of a project or where the 

 life of the wood is to be less than a few months. It can also be used in 

 any situations where the wood can be protected either by a covering, for 

 example interior framing of a building, or where it is to be painted and 

 maintained in a painted state for the projected life of the installation. 

 Untreated dimension lumber should not be used in direct contact with the 

 ground or sea water. Untreated dimension lumber is used in form work for 

 concrete. It is also used in a variety of ways such as for dunnage or 

 machinery supports. 



Foundations and sill plates for frame buildings are usually pressure 

 treated with chromated copper arsenate. Any use where contact with the 

 earth exposes the lumber to rot, fungus, or insect attack requires treatment 

 to obtain a satisfactory useful life. Specific treatment would be determined 

 by the conditions of service. Exposed uses subject to severe weathering or 

 prolonged (or periodic) immersion in seawater should be pressure treated 



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