must be designed to withstand the deep ocean environment over long time periods. Reliable experi- 

 mental data are now in hand for the dynamic response of and flow-induced forces on a model scale. 

 Based upon these experiments, semi-empirical prediction models have been developed and favorably 

 compared with field test data. 



1.3 NAVFAC/CEL Research Program in Cable Strumming. During the late 1960's and early 1970's the 

 Navy conducted several experiments on large, three-dimensional moored cable structures. These struc- 

 tures were intended to serve as platforms for a variety of oceanographic sensors. In general, the perfor- 

 mance of these cable structures was substantially less than desired, due primarly to a lack of adequate 

 means for calculating the dynamic response of the structure during installation or while in place in the 

 water column. In recognition of the Navy's inadequate capabilities for the design and prediction of the 

 performance of moored cable structures, the Civil Engineering Laboratory (CEL) of the Naval Facilities 

 Engineering Command (NAVFAC) initiated a research program to develop effective means for the 

 analysis of the dynamic response of complex, three-dimensional moored cable structures in the ocean. 



The objectives of the strumming portion of the research were twofold: (1) development of a capa- 

 bility to predict the strumming response (i.e., deflection, vibration amplitude and frequency, drag force) 

 of cable networks which have cable segments at arbitrary orientation to the flow, in taut or catenary 

 configuradons with or without attached masses, subjected to a current which may vary in magnitude or 

 direction along the cable length; and (2) development of techniques which can be used to suppress 

 cable strumming. 



The research plan reviewed the analytical models then available (1974) for the calculation of 

 strumming and concluded that the so-called semi-heuristic approach offered the most promise for 

 extension to the strumming of cables. At the time the plan was written, the models had been applied 

 only to two-dimensional rigid cylinders. The first step in model development, then, was the extension 

 of the models to taut, flexible cables in uniform, perpendicular currents. Succeeding efforts extended 

 the models to yawed cables in uniform currents, slack cables and to cables in nonuniform currents. 



