CONCEPTS IN DESIGN OF COASTAL STRUCTURES

Abstract

Certain design of the existing and proposed coastal structures for lateral loading in the United States is presently based upon the use of timber which is structurally inefficient in the elastic range. Figure 1, for example, indicates the plan of timber pile structure. This is a low- capacity dolphin composed of 19 piles, where piles in line of load carry two times axial load and three times larger shear than next piles in line of load. A relatively small load will be conducive to yield in the tension or compression members. Repetitive loading will gradually cause collapse of such structure. Being inefficient in the elastic range, timber structures may nevertheless, be adequate to provide safety for condition of shallow water, moderate wind pressures, moderate tides, and for moderate cross and reversing currents. However, such factors as: traffic safety, the possibility of marine borer attack, the location of structures in greater water depths, where they are exposed to waves, currents, tides, winds, and floating objects, indicate a need for larger capacity, more reliable and functional coastal structures consistent with the growing requirements.