bound together to create a, single structure. Small structures such as sand 

 fences may be a series of independent pieces or sections of a material 

 acting in an independent manner. 



Structures built of stone, earth and asphalt are generally not capable 

 of resisting tensile stress. They are capable of taking loads in compression, 

 shear and impact only and must be designed accordingly. Concrete and wood 

 may or may not be subjected to tensile stress or bending moments. If 

 concrete is subjected to such stress, reinforcing steel or prestressed 

 cable must be employed to carry the tensile load. Steel is capable of 

 withstanding all types of stress when properly designed. The sections flex 

 or deflect when subjected to bending loads and this movement should be 

 considered in the design phase. Synthetics, particularly the sandbag and 

 filter-cloth materials, are mainly subjected to tension, impacts, flexing, 

 and fatigue. They are seldom required to accept a compressive load. 



3. Nonstructural Properties . 



a. Durability . Durability is the ability of a material to withstand 

 the effects of service conditions to which it is exposed. Many laboratory 

 tests have been devised for measuring durability of materials but it is 

 extremely difficult to obtain a direct correlation between laboratory tests 

 and field use. Due to the severe coastal environment it is important that 

 field experience be carefully assessed in selecting materials for coastal 

 structures. For a coastal structure to function properly the planned 

 structural life must be known; a structural life projected for a short term 

 (e.g., less than 10 years) may have a major impact on cost and material 

 selection for the structure. The location of the structure with respect to 

 local resources and materials will also impact on the selection of construc- 

 tion materials. 



Durability is generally related to the desired lifespan of the structure 

 and the relation between first costs and maintenance. Among the stones, 

 igneous rock is usually the most durable rock. Depending on makeup, it may 

 be extremely durable or, after a few years, may fracture and partially 

 disintegrate. Sedimentary rock should be examined very carefully as it is 

 usually stratified, may not be well consolidated, and is subject to failure 

 through shear stress, impact, fracture due to changes of water content, or 

 chemical deterioration. 



Earth is generally considered durable unless changes in water content 

 or chemistry reduce grain size to the silt and clay range, resulting in 

 plastic flow. 



Concrete is considered durable and will generally last the planned life 

 of the structure so long as it is not exposed to adverse chemical reaction 

 or excessive abrasion. 



Asphalt is generally not considered a durable material. It is of low 

 strength in compression or tension, subject to chemical reactions, and not 

 resistant to impact or abrasion. 



Steel is considered durable if properly maintained. However, it is 

 subject to rapid deterioration through corrosion and abrasion. Abrasion 



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