Change Order "O" to Contract NOy-12561, under which the Laboratory is now operating, provides as a general objective the investigation of the forces and pressures exerted by waves on fixed plane barriers inclined at any angle to the sea surface, and on stepped or off-set plane barriers. In keeping with this objective, the Laboratory
is endeavoring to develop a program which will combine a basic investigation of the mechanics of wave-induced forces with the production of immediately useful data. It is expected, for instance, that the results of experimental farce and pressure measurements on plane barriers, aside from their scientific value, can be used with
profit in calculating the stability of gravity-type or caisson breakwaters against sliding and overturning.
Since this program represents a new field of work for this
Laboratory, the initial portion of the contract period has been devoted to the alteration of existing laboratory equipment, and the design and construction of required new equipment. In all of the~ modification and development of force and pressure measuring equipment, an effort has been made to design for maximum flexibility. Thus, the resulting basic units can be easily adapted to the various specific phases of the current or future investigations, such as
breaking and non-breaking wave conditions, and many configurations of structures for which force or pressure data will be of interest. At this time, all equipment for the pressure measuring and orbit investigation programs has been completed, and work on these programs has begun. The force measuring apparatus is under construction, with
completion estimated as June 1, 1953.
In view of the considerable investment in time and funds made to equip the Laboratory for this new type of investigation, this report has been prepared to describe in some detail the alteration of existing equipment and the development of new equipment
